Auto Focus Work Out

Auto Focus Work Out

My recent summer trip to Flatanger in Norway, and to the famous “Eagle Man of Norway” Ole Martin Dahle, proved, as ever, a severe test of the auto focus capabilities of the gear!

We had 4 guys on the trip, 3 Nikon and 1 Canon, and White-tailed Eagles doing more than 40mph and turning on a dime is one of the hardest tests for auto focus tracking and lock on that you can imagine – especially when it’s all done hand held from a boat that’s rolling around in the sea swell.

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The Guys – yours truly, Malcolm Clayton and Paul Atkins; and Mohamed El Ashkar (all the way from Cairo!) and our Cambridge “Don” – all trips should have one – Jamie Gundry. Photo by Ole Martin Dahle.

We had a conglomeration of D4’s, D800E’s and 200-400 f4’s, with a smattering of 300mm and 400mm f2.8’s – and then there was Mohamed with his solitary 1Dx and 300 f2.8.

And our target:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings

Say “Hello” to “Brutus” – an eagle who lives up to his name for sure – a total brute, especially to a boat full of daft photographers! CLICK for larger view.

Just to set the scene with regard to the technical side of things; birds fly into the wind given the choice, and the sun is wherever it decides to be! So the boat driver – Ole – always needs to position the boat so that “wind and sunlight” are coming from pretty much the same direction, otherwise the birds are not front-lit and cast their own shadows across themselves. In other words the images look like crap!

Some birds come towards the boat, take the fish and then turn away; some will do their approach parallel to the boat; and gits like Brutus will fly low and fast straight at you, pick the fish and then turn straight for the boat and climb.

But no matter how they choose to approach the camera boat all the birds pick the fish and go back to where they’ve come from.

Ole has intimate knowledge of these birds as individuals, and so has a damn good idea of what they will do as they come to the boat.  This enables him to manoeuvre the boat for the best shots, and this skill is what you pay for.

Perhaps by now you’ve got the general feel for the situation – a boat that’s subject to wave motion and which might suddenly go backwards 10 yards through its own wake – not the steadiest of camera platforms!

Couple that with trying to make the auto focus lock on and track the bird, and maintain a modicum of composition – it’s just damned hard work.

Photographing anything that’s moving is hard work; moving erratically is even harder; and hand holding on an oscillating camera platform makes the job beyond hard.  This style of shooting will NEVER yield vast rafts of sharp sequential images – anyone who tells you different is an outright liar. Christ, even licensed FIA F1 ‘togs are on “easy street” by comparison.

Auto focus cannot be set up perfectly for this sort of situation, but understanding it is a MUST if you want to maximise the opportunity.

Auto Focus Choices

There are 3 main things that control the effectiveness of auto focus and AF tracking:

AF Area Mode

AF Tracking Lock-on interval

Frame Rate

(Bare in mind I’m talking Nikon here, but sorting Mohameds’ 1Dx out showed my that Canon AF is pretty much the same).

Now I dealt with the latter in a previous post HERE and so we need to concentrate here on AF area modes in the main.

Let’s look at what we have to work with on a Nikon body – in this case a D4:

Firstly, the AF sensor layout.

All 51 focus sensors, and there approximate layout in relation to the image frame:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings

All 51 of the Nikon Multi Cam 3500 FX focus sensors – both cross and linear sensors depicted.

Just the Cross-type Sensors:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

The 15 Cross type focus sensors on the Nikon Multi-Cam 3500 FX unit.

The Linear-type Sensors:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

The 36 Linear type focus sensors on the Nikon Multi-Cam 3500 FX unit.

Single Area AF

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

Single Area, or single point AF.

9 Point Dynamic Area AF:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

9 Point Dynamic Area AF

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

9 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

21 Point Dynamic Area AF:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

21 Point Dynamic Area AF

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

21 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

51 Point Dynamic Area AF:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

51 Point DA AF as displayed in the viewfinder (drop shadows added in Photoshop behind the dots to aid visibility in this article).

As a stills photographer you are using what’s called Phase Detection auto focus (that’ll be another blog post topic!) but it still relies on a mix of contrast,luminosity and colour to work out what it should be concentrating on in the frame.

Consider the following 2 images, A & B:

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

A. Dark Subject and Light Background.
Subject itself is low contrast, background water is higher contrast. Subject is at 15 meters, Focal Length is 240mm

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

B. Light Subject against a Dark Background.
Subject now has a slightly higher contrast, and background is lower contrast. Subject 29 meters, Focal length 360mm

Auto focus is dumb; just plain stupid, left to its own devices.  It, like me (yep, me dumb too!) favours lighter things with a higher degree of contrast.  The lighter something is then the brighter and more saturated it colour is, and this in turn gives it higher localised contrast.

Auto focus will be happier locking on to and tracking Eagle B than Eagle A.

In A, the AF will want to switch to the lighter, more contrasty water behind the bird – unless of course you “hobble it” and stop it from doing so…

And you stop it by BLINDING IT – in other words use LESS active auto focus points!

“If it ain’t got ’em it can’t switch to ’em!”

If all the AF points in use are on the important part of the subject (the EYE in this case) then there’s little or no chance of the auto focus switching to somewhere you don’t want it to go to.

In a perfect world we’d all be using Single Area AF on a tripod and panning away quite happily keeping that single sensor on the targets eye……………oh I wish!!!!!!

51 point AF is out for this sort of work – with what I’ve just written you should now easily understand why.

So we are down to either the 9 point or 21 point Dynamic Areas.

It all comes down to two things:

  • How steady you can keep the camera.
  • How big in the frame the birds are – in other words, subject distance.

But accuracy of auto focus will always be improved by using the least number of sensors you can get away with.

 

Image A. is at 240mm and a subject distance of 15 meters, and Image B. is at 360mm and a subject distance of 29 meters.  Both images were shot using 21 point Dynamic Area AF, 1/2000th @ f7 and 1600ISO.

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

21 point AF, 15 meters and 240mm focal length.

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

21 point AF, 29 meters and 360mm focal length.

On the upper detail image there’s one, perhaps two of the 21 sensors that are NOT on the subject.

On the second image there are at least 9 sensors out of the 21 in the group that are NOT on the bird.

If the bird in image A. had been 29 meters away I’ll guarantee it would have been out of focus – why?

  • Lack of good directional light.
  • Poor subject contrast and illumination.
  • Brighter, higher contrast background.
  • More sensors “Off Target”.

And the auto focus hasn’t wanted to wander to the background on image B. because there’s nothing there for it to favour over the main subject.

How Dynamic Area AF Works

9 point DA auto focus uses the single AF point that you select, but activates the 8 points surrounding it.  If you, or the subject, or both, move so that the single point you selected comes “off target” then one of those 8 surrounding points will “cover” the error and maintain focus lock and tracking until you get back on target.

In 9 point DA, auto focus ALL the sensors activated are “cross type” sensors, assuming you use a sensor on the vertical center line of the AF grid.

In 21 point DA, auto focus is still centered on the single sensor you select, but now the surrounding 20 are activated. But at least 6 of these sensors will be linear, not cross type sensors.

Auto Focus Senor Types – Cross and Linear (line).

This is going to be immensely paraphrased!

AF sensors need to see edge detail in order to work. A linear sensor can work more effectively when the edge it’s looking at is perpendicular to it.

The more an edge is parallel to said line sensor then the harder time it has in discerning when said edge is sharp or not.

But if we add 2 line sensors together at right angles to each other, then an edge that is parallel to one line is perpendicular to the other – so edge detection is greatly enhanced.

In an ideal scenario 9 point Dynamic Area AF, centered in the middle of the view finder and kept on the eagles head would be the ideal way to go, but with the other circumstances of:

  • Moving camera platform
  • Potential closeness of subject (sub 15 meters possible)

then 9 point DA might be a wee bit tight on both counts, and 21 point makes more sense from a tracking and shooting perspective.

But it leads to an initial problem with the auto focus acquiring the target in the first place.  You have to pick these eagles up quite a way out, and if one is coming low to the water then there is possibly too much in the frame to act as a distraction to the auto focus unit itself; though this isn’t quite such an issue if the bird is high in the sky.

So my recommendation for any form of bird-in-flight photography is to start out at 9 point DA and see how you get on!

There is always the AF Tracking Lock On feature that you can deploy in order to “hobble” the AF unit from switching  to subjects closer to or further away, but if I’m honest I find this the most sticky and difficult aspect of the Nikon system to get a precise handle on.  It does exactly “what it says on the tin” but it’s the “when” and “how much by” bits that have me slightly guessing.

Sometimes I put it on long and it basically waits for perhaps 4 or 5 seconds before it tries to switch focus, while at other times it does so in less than half the time.  Sometimes I feel it actually diminishes the effectiveness of the “predictive” side of the auto focus tracking unit.

But if I turn it off when hand holding the camera for flight shots then everything turns to crap – so I turn it back on again!

Again, my base recommendations for this are SHORT to NORMAL and see how things go.

One thing that can have a considerable impact on the way you perceive your auto focus effectiveness is how you have your AF release priority set up (CS a1).

There are 4 options:

  • Release
  • Focus+Release
  • Release+Focus
  • Focus

By default this is set to FOCUS.  With the default setting, it’s theoretically impossible to take a soft shot.  But in practice that’s not so simple, and I’ve taken many a soft shot when the D4 “thinks” things are sharp; though in the main, that seems to have been cured the minute we got trap focus back with the latest firmware upgrade.

Release means the camera will take shots irrespective of focus being acquired or not.  I NEVER use this option.

Focus+Release means that the first frame will only be taken once focus is acquired, and subsequent frames will be taken irrespective of focus.  This is one of my preferred options when everything is unstable – that first frame hopefully sets up the auto focus and AF tracking and so everything SHOULD keep the subsequent frames sharp – please note the use of the word “should”!

Both the above release priority modes do NOT slow the frame rate.

Release+Focus – works the opposite way to Focus+Release – it does slow the frame rate down giving the mirror more down-time and so the auto focus system has more time to work.  This is my other preferred option, the one I use when the “action” may not be as repeatable.

Focus – This is the option I deploy when shooting from a tripod or when the action is not quite so fast-paced.  Again, this option slows the frame rate.

The Back Button Auto Focus Option

I always use the back button for auto focus activation.  There are plenty of arguments for doing this, but I just feel it’s darn right more efficient than having AF activation on the shutter button.  Just don’t forget to turn AF/Shutter ON to OFF in the menu, otherwise you are just wasting time and effort!

Conclusion

A lot of folk feel that their auto focus is flawed; but more often it is they and their setup choices which are flawed.

There is no blanket panacea or magic bullet setting for your AF system – as with everything else you have to constantly evaluate the light around you, anticipate the shot and make the necessary changes to setup – otherwise it’s going to be a sad day.

But knowing how your gear works and how it reacts under different scenarios is the “meat and two veg” of good photography.  Couple that with shot anticipation and the proper corrective measures and it’s off home for tea and medals!

But above all, remember to have a laugh – you’re a long time dead……..

wildlife photography,auto focus,Nikon,D4,Andy Astbury,eagle,Norway,workshop,camera settings,Nikon Multi-Cam 3500 FX unit

“GIMME SOME, YOU MEAN BARSTARD!”

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Parallel Horizontals.

Quite often when shooting landscapes, or more commonly seascapes, you may run into a problem with parallel horizontals and distortion between far and near horizontal features such as in the image below.

Parallel horizontals that are not parallel - but should be!

Parallel horizontals that are not parallel – but should be!

This sort of error cannot be fully corrected in Lightroom alone; we have to send the image to Photoshop in order to make the corrections in the most efficient manner.

Here’s a video lesson on how to effectively do just that, using the simplest, easiest and quickest of methods:

You can watch the video at full size HERE – make sure you click the HD icon.

This is something which commonly happens when photographing water with a regular shaped man-made structure in the foreground and a foreshortened horizon line such as the receding opposite shore in this shot.  But with a little logical thought these problems with parallel horizontals being “out of kilter” can be easily cured.

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Flash Duration – How Fast Can We Go

Flash duration – how long the burst of photons from flash actually lasts, does seem to get a lot of people confused.

Earlier this year I posted an article on using flash HERE where the prime function of the flash was as a fill light. As a fill, flash should not be obvious in the images, as the main lighting is still the ambient light from the sun, and we’re just using the flash to “tickle” the foreground with a little extra light.

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Flash as “fill” where the main lighting is still ambient daylight, and a moderate shutter speed is all that’s required. 1/800th sec @ f8 is plenty good enough for this shot.

Taking pictures is NEVER a case of just “rocking up”, seeing a shot and pressing the shutter; for me it’s a far more complex process whereby there’s a possible bucket-load of decisions to be made in between the “seeing the shot” bit and the “pressing the shutter” bit.

My biggest influencers are always the same – shutter speed and aperture, and the driving force behind these two things is light, and a possible lack thereof.

Once I make the decision to “add light” I then have to decide what role that additional light is going to take – fill, or primary source.

Obviously, in the shot above the decision was fill, and everything was pretty straight forward from there on, and aperture/shutter speed  selection is still dictated by the ambient lighting – I use the flash as a “light modifier”.

The duration of the flash is controlled by the TTL metering system and it’s duration is fairly irrelevant.

Let’s take a look at a different scenario.

flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

The lovely Jo doing her 1930’s screen icon “pouty thing”. Flash is the ONLY light source in this image. 1/250th @ f9 ISO 100.

In this shot the lighting source is pure flash.  There’s very little in the way of ambient light present in this dark set, and what bit there is was completely over-powered by the flash output – so the lighting from the Elinchrom BX 500 monoblocks being used here is THE SOLE light source.

Considerations over the lighting itself are not the purpose of this post – what we are concerned with here are the implications for shutter speed due to flash synchronization.

The flash units were the standard type of studio flash unit offering no TTL interface with the camera being used, so it’s manual everything!

But the exposure in terms of shutter speed is capped at 1/250th of a second due to the CAMERA – that is it’s highest synch speed.

The focal length of the lens is 50mm so I need to shoot at around f8 or f9 to obtain workable depth of field, so basic exposure settings are dictated.  This particular shot was achieved by balancing the light-to-subject distance along the lines of the inverse square law for each light.

But from the point of view of this post the big consideration is this – can I afford to have movement in the subject?

At 1/250th sec you’d think not.  Then you’d think “hang on, flash durations are a lot faster than that” – so perhaps I can…..or can I ?

Flash Duration & Subject Movement

Flash duration, in terms of action-stopping power, is not as simple or straight forward as you might think.

Consider the diagram below:

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Flash Power Output curve plotted against Output duration (time).

The grey shaded area in the diagram is the “power output curve’ of the flash.

Most folk think that a flash is an “instant on, instant off” kind of thing – how VERY wrong they are!

When we set the power output on either the back panel of our SB800/580EX etc, or on the power pack of a studio flash unit, or indeed any other flash unit, we are setting a peak output limit.

We might set a Nikon SB800 to 1/4 power, or we might set channel B output on a Quadra Ranger to 132Watt/sec, but either way, we are dictating the maximum flash output power – the peak output limit. The “t 5 time” – or to be more correct the “t 0.5 time” is the total time duration where the flash output is at 50% or above of the selected peak output limit we set.

Just to clarify: we set say, 1/4th power output on the back of a Canon 580EX – this is the selected peak output limit. The t5 time for this is the total time duration where the light output is at or above 50% of that selected 1/4th power – NOT 50% of the flash units full power output – do not get confused over this!

So when it comes to total “light emission duration” we’ve got 3 different ways of looking at things:

  1. Total – and I mean TOTAL – duration; the full span of the output curve.
  2. T 0.5 – the duration of the flash where its output is at 50% or above that level set by the user – the peak output limit.
  3. T 0.1 – the duration of the flash where its output is at 10% or above that level set by the user.

Anyone looking at the diagram above can see that the total output emission time/flash duration is A LOT LONGER than the t5 time.  Usually you find that t5 times are somewhere around 1/3rd of the total emission time, or flash duration.

Getting back to our shot of Jo above, if my memory serves me correctly the BX heads I used for the shot had a t5 time of around 1/1500th sec.  So the TOTAL duration of the flash output would be around 1/500th sec.

So I can’t afford to have any movement in the subject that isn’t going to be arrested by 1/500th sec flash duration, let alone the 1/250th shutter speed.

Why? Well that 1/250th sec the shutter is open will comprise of 1/500th sec of flash photons entering the lens, and 1/500th sec of NOTHING entering the lens but AMBIENT LIGHT photons.

Let us break flash output down a bit more:

In the previous article I mentioned, I quoted a table of Nikon SB800 duration times.  At the top of the table was the SB800 1/1 or full output power flash duration.  All times quoted in that table were t5 times.

The one I want to concentrate on is that 1/1 full power t5 time of 1/1050th sec.

Even though Nikon try to tempt you into believing that the flash only emits light for 1/1050th sec it does in fact light the scene for a full 1/350th sec – most flash manufacturers units are quoted as t5 times.

Now in most cases when you might employ flash – which let’s face it, is as some sort of fill light in a general ambient/flash mixed exposure, this isn’t in reality, a big problem.  Reduced power multiple pulse AutoFP/HSS also makes it not a problem.

But if you are trying to stop high speed action – in other words “freeze time”, then it can become a major headache; especially when you need all the flash power you can get hold of.

Why? Let’s break the diagram above down to basics.

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The darker shaded area represents the “tail” of the flash output – the area that can cause many problems when trying to stop high speed action.

  • The first 50% of the total light output is over and finished in the first 1/1050th of the total flash duration.
  • The other 50% of the total light output takes place over a further 1/525th sec, and is represented by the dark grey area – let’s call this area the flash “output tail”.  Some publications & websites refer to this tail as after-glow.  I always thought that ‘after glow” was something ladies did after a certain type of energetic activity!
  • The light will continue to decay for a full 1/525th sec after t5, until the output of light has died down to 0% and the full “burn time” of 1/350th sec has been reached.

That’s right – 1/1050th + 1/525th = 1/350th.

So, if our shutter speed is 1/350th sec or longer we are going to see some ghosting in our image caused by the movement of the subject during that extra 1/525th sec post t5 time.

I need to point out that most speedlight type flash units are “isolated-gate bipolar transistor” devices – that’s IGBT to you and me. Einstein studio flash units are also IGBT units – I’ll cover the implications of this in a later post, but for now you just need to know that the IGBT circuitry works to eliminate sub t5 output BUT doesn’t work if your speedlight is set to output at maximum power.  And if you need access to full 1/1 power with your speedlights for any reason then IGBT won’t help you.

Let’s see the problem in action as it were:

flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

A bouncing golf ball shot at 1/250th sec using full power output on an SB800.
The ball is moving UPWARDS.
The blur between points A & B are caused by the “tail” or “after-glow” of the flash.

And the problem will be further exacerbated if there is ANY ambient light in scene from a window for instance, as this will boost the general scene illumination during that “tail end” 1/525th sec.

We might be well advised, if using any form of non-TTL flash mode, to use a shutter speed equal to, or shorter in duration to the t5 time, as in the shot below:

flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

A bouncing golf ball shot at 1/2000th sec using full power output on an SB800.

All I’ve done in this second shot is go -3Ev on the shutter speed, +1Ev on the aperture and +2Ev on ISO speed.

Don’t forget, the flash is in MANUAL mode with a full power output.

With the D4 in front-curtain synch the full power, 1/350th sec flash pulse begins as the front shutter curtain starts to move, and it “burns” continuously while the 1/2000th sec “letter-box” shutter-slot travels across the sensor.

In both shots you may be wondering how I triggered the exposure. Sitting on the desk you can see a small black box with a jack plug sticking out the back – this is the audio sensor of a TriggerSmart audio/light/Infra Red combined trigger system.  As the golf ball strikes the desk the audio sensor picks up the noise and the control box triggers the camera shutter and hence the flash.

Hardy, down at the distributors,Flaghead, has been kind enough to send me one of these systems for incorporation into some long-term photography projects, and in a series of high speed flash workshops and training tutorials.  And I have to say that I’m mighty impressed with the system, and at the retail pricing point ownership of this product is a no-brainer.  The unit is going to feature in quite a few blog post in the near-future, but click HERE to email Hardy for more details.

Even though I constantly extol the virtues of the Nikon CLS system, there comes a time when its automatic calculations fight AGAINST you – and easy high speed photography becomes something of a chore.

Any form of flash exposure automation makes assumptions about what you are trying to do.  In certain circumstances these assumptions are pretty much correct.  But in others they can be so far wide of the mark that if you don’t turn the automation OFF you’ll never get the shot you want.

Wresting full control over speed lights from the likes of Nikons CLS gives you access to super-highspeed flash durations AND high shutter speeds without a lot of the synching problems incurred with studio monoblocks.

Liquid in Motion,flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

Liquid in Motion – arrested at 1/8000th sec shutter speed using SB800’s at full 1/1 power.

Liquid in Motion,flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

Liquid in Motion – arrested at 1/8000th sec shutter speed using SB800’s at full 1/1 power. A 100% crop from the shot above.

Liquid in Motion,flash duration,fill flash,flash,shutter speed,photography,Andy Astbury,digital photography,wildlife photography

“Scotch & Rocks All Over The Place”
Simple capture with manual speed lights at full power and 1/8000th shutter speed.

The shots above are all taken with 2x SB800s lighting the white background and 1 heavily defused SB800 acting as a top light.

One background light is set at 1/1 manual FP, the other to manual 1/1 SU-4 remote.  The top light is set to 1/8 power SU-4 remote.

The majority light in the shot is in fact that white background – it’s punching light back through the glass and liquid splash – the subject is backlit.

So, that background is being lit for a full 1/350th of a second.

But shooting in front curtain synch I’m using 1/8000th sec as a shutter speed, an exposure duration 3 stops shorter than the flash unit t5 time for full power. So in effect I’m using the combined background flash units as a very short-term continuous light source which lasts for 1/350th of a second, but the camera is only recording the very first 1/8000th sec – in other words, photons are still leaving the flash AFTER the rear shutter curtain has closed and the exposure is finished.

Finally, the shutter and flash are triggered by dropping the faux crushed ice through the IR sensor beam of the TriggerSmart unit.

This is very much along the lines of what’s termed HYPERSYNCH – a technique you can use with conventional slow burn studio flash units and certain types of 3rd party trigger units such as Pocket Wizards – but that’s yet another story, and is fraught with synch problems that you have program out of the system using the Pocket Wizard utility.

So, there’s more to come from me about flash in future posts, but for now just remember – there’s not a lot you can’t do with speed lights – as long as you’ve got enough of the little darlings!

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Trap Focus

Trap Focus on the Nikon D4

Trap focus comes to my D4 – Yay!!!!!!!!

What was it Nikon said – “we left it off the D4 because no one wanted it”….or words to that effect.

Well, with today’s (March 18th 2014) update version 1.10 trap focus is back – in a fashion.

What is trap focus some may ask.  Well it’s basically pre-focusing on a particular distance or spot where you expect the subject to be or to pass through.

As the subject enters the frame and gets closer to the camera it’s also getting closer to the pre-focused distance, and when it reaches the set focus distance the camera actually detects the subject/image is sharp and so takes the shot.

Basically you sit there with the shutter button fully depressed, but no shots get taken until the camera AF system deems the subject is now in focus.

It’s a technique that a lot of sports photographers find very useful, but I find it has very limited use for my wildlife & natural history work.  Having said that, it’s got me out of a bind more than once over the years, but ever since the D4 came out you’ve not been able to use it.

The failing lay in the flawed D4 focus priority – even if you told it to only trip the shutter when the image was deemed ‘in focus’ by setting CS a1 & a2 to FOCUS, it would still fire as if a1 and a2 were set to release priority.

But the new firmware update v1.10 has given trap focus back to the D4, but before you start jumping up and down and getting all excited you need to know how to set it up, and bare in mind that “as a technique” trap focus might not suit what you had in mind.

Setup for D4 Trap Focus

  1. Update firmware to v1.10 – read the instructions FULLY before you attempt this, otherwise you may need another camera!
  2. Go to Custom Settings a2 AF-S priority selection and set to FOCUS.
  3. Go to Custom Settings a4 AF activation and set to AF-ON only – this takes to AF activation away from the shutter release button.
  4. Put a wide angle lens on the camera.
  5. Set the lens focus switch to M/A
  6. Set the D4 focus mode selector (the lever on left side of the body front) to AF
  7. Press the AF mode button and rotate the Command Dial (back one) to select AFS and NOT AFC.
  8. Rotate the Sub Command Dial (front one) to select S (single) and NOT Auto.
  9. Focus on your computers monitor screen using either the manual focus ring of the lens or the rear AF-ON button next to the Command Dial.
  10. If you’ve pressed the latter TAKE your thumb OFF!
  11. Move the camera directly away from the computer monitor screen so the image in the viewfinder goes soft.
  12. Jam your finger down on the shutter release. Nothing happens (if it does then start again!).
  13. Keeping that shutter button depressed and NOT touching the lens or AF button, move back towards the computers monitor screen – the shutter will fire when the monitor screen is sharp.

Got that?  Good!  Oh, and by the way, the award-winning shot you just missed – it would have been epic!

Now you’ve got a D4 that does trap focus.

Now for the trap focus caveats:

Trap Focus only works in AFS – not in AFC.

Trap Focus only works with a single AF sensor, AFS-S – so correct prediction of that one AF sensor/subject alignment to get the required ‘bits” in sharp focus and DoF is going to be difficult.

wildlife photography, common Kestrel, photography technique,manual focus trap,trap focus

Common Kestrel Landing
©Andy Astbury/Wildlife in Pixels

Do NOT think you can pull this wildlife shot off using TRAP FOCUS.

By the time the camera has detected the sharp focus and got over the system lock time and triggered the shutter, the bird will be way closer to the camera – and sharp focus in the resulting image will be behind the tail!

This shot is done with a manual focus trap – a completely different technique, as described HERE

The subject is too small and so to close to the camera and 500mm lens for trap focus to work effectively.

However, if you are doing sports photography for instance, you are imaging subjects that are much bigger and a lot further away.

A 500mm f4 on an FX body has over 2 meters depth of field at f5.6 when focused at 40 meters.  Take a baseball match for instance – not that I’ve ever covered one mind!

Set the single AF sensor focus distance at home plate.

Then tilt the camera up slightly, or move the sensor with the Dpad so it can’t see/is not overlaying what you just focused on. Hold the shutter button down and wait for a player to make a dive for home plate.  As he enters the area of the AF sensor the camera will fire continually if you’re in continuous shooting mode, and will only stop when the camera detects focus has been lost.

Works like a charm!

The key thing is that the depth of field generated by the focus distance makes trap focus work for you – at much shorter distances where depth of field is down to an inch or so if you’re lucky, then couple that with a fast subject approach speed, and trap focus will fall down as a reliable method.

If I’m doing studio flash work like this:

WIP00048398

which is never often enough any more! – I sometimes find it useful to use trap focus because it can help doing hand held work under the lowish flash unit modelling lights when you want to make sure eyes are sharp.

Using Trap Focus in a sort of 'bastardised' manner can help you maintain sharp focus on models eyes whilst giving you freedom to move around, change composition, zoom etc. by controlling the sharpness of the image with the lens focus ring.

Using Trap Focus in a sort of ‘bastardised’ manner can help you maintain sharp focus on models eyes whilst giving you freedom to move around, change composition, zoom etc. by controlling the sharpness of the image with the lens focus ring.

Like I said earlier, it’s a technique that can get you out of trouble every now and again, but up until today you hadn’t got recourse to it on the D4.

But you seriously need to understand the limitations of trap focus deployment before you rush out and use it – you could be very disappointed with the results, and it’ll be all your own fault for trying to bang a square peg through a round hole.

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What Shutter Speed?

Shutter speed, and the choices we make over it, can have a profound effect on the outcome of the final image.

Now everyone has a grasp of shutter speed and how it relates to subject movement – at least I hope they do!

We can either use a fast shutter speed to freeze constant action, or we can use a slow shutter speed to:

  • Allow us to capture movement of the subject for creative purposes
  • Allow us to use a lower ISO/smaller aperture when shooting a subject with little or no movement.

 

Fast Shutter Speed – I need MORE LIGHT Barry!

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels

1/8000th sec @ f8, Nikon D4 and 500mm f4

Good strongish sunlight directly behind the camera floods this Red Kite with light when it rolls over into a dive.  I’m daft enough to be doing this session with a 500mm f4 that has very little in the way of natural depth-of-field so I opt to shoot at f8.  Normally I’d expect to be shooting the D4 at 2000iso for action like this but my top end shutter speed is 1/8000th and this shutter speed at f8 was slightly too hot on the exposure front, so I knocked the ISO down to 1600 just to protect the highlights a little more.

Creative Slow Shutter Speed – getting rid of light.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels

1/5th sec @ f22

I wanted to capture the movement in a flock of seagulls taking off from the water, so now I have to think the opposite way to the Kite shot above.

Firstly I need to think carefully about the length of shutter speed I choose: too short and I won’t capture enough movement; and too long will bring a vertical movement component into the image from me not being able to hold the camera still – so I opt for 1/5th sec.

Next to consider is aperture.  Diffraction on a deliberate motion blur has little impact, but believe it or not focus and depth of field DO – go figure!

So I can run the lens at f16/20/22 without much of a worry, and 100 ISO gets me the 1/5th sec shutter speed I need at f22.

 

Slow Shutter  Rear Curtain Synch Flash

We can use a combination of both techniques in one SINGLE exposure with the employment of flash, rear curtain synch and a relatively slow shutter speed:

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels

6/10th sec @ f3.5 -1Ev rear curtain synch flash

A technique the “Man Cub” uses to great effect in his nightclub photography, here he’s rotated the camera whilst the shutter is open, thus capturing the glowing LEDs and other highlights as circular trails.  As the shutter begins to close, the scene is lit by the 1/10,000th sec burst of light from the reduced power, rear curtain synched SB800 flash unit.

But things are not always quite so cut-and-dried – are they ever?

Assuming the lens you use is tack sharp and the subject is perfectly focused there are two factors that have a direct influence upon how sharp the shot will be:

  • System Vibration – caused by internal vibrations, most notably from the mirror being activated.
  • Camera Shake – caused by external forces like wind, ground vibration or you not holding the camera properly.

Shutter Speed and System Vibration

There was a time when we operated on the old adage that the slowest shutter speed you needed for general hand held shooting was equal to 1/focal length.

So if you were using a 200mm lens you shot with a minimum shutter speed of 1/200th sec, and, for the most part, that rule served us all rather well with 35mm film; assuming of course that 1/200th sec was sufficient to freeze the action!

Now this is a somewhat optimistic rule and assumes that you are hand holding the camera using a good average technique.  But put the camera on a tripod and trigger it with a cable or remote release, and it’s a whole new story.

Why?  Because sticking the camera on a tripod and not touching it during the exposure means that we have taken away the “grounding effect” of our mass from the camera and lens; thus leaving the door open to for system vibration to ruin our image.

 

How Does System Vibration Effect an Image?

Nowadays we live in a digital world with very high resolution sensors instead of film. and the very nature of a sensor – its pixel structure (to use a common parlance) has a direct influence on minimum shutter speed.

So many camera owners today have the misguided notion that using a tripod is the answer to all their prayers in terms of getting sharp images – sadly this ain’t necessarily so.

They also have the other misguided notion that “more megapixels” makes life easier – well, that definitely isn’t true!

The smallest detail that can be recorded by a sensor is a point of light in the projected image that has the same dimensions a one photosite/pixel on that sensor. So, even if a point is SMALLER than the photosite it strikes, its intensity or luminance will effect the whole photosite.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images.

A point of light smaller than 1 photosite (left) has an effect on the whole photosite (right).

If the lens is capable of resolving this tiny detail, our sensor – in this case (right) – isn’t, and so the lens out-resolves the sensor.

But let’s now consider this tiny point detail and how it effects a sensor of higher resolution; in other words, a sensor with smaller photosites:

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

The same detail projected onto a higher resolution sensor (right). Though not shown, the entire photosite will be effected, but its surface area represents a much small percentage of the whole sensor area – the sensor now matches the lens resolution.

Now this might seem like a good thing; after all, we can resolve smaller details.  But, there’s a catch when it comes to vibration:

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

A certain level of vibration causes the small point of light to vibrate. The extremes of this vibration are represented by the the outline circles.

The degree of movement/vibration/oscillation is identical on both sensors; but the resulting effect on the exposure is totally different:

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

The same level of vibration has more effect on the higher resolution sensor.

If you read the earlier post on sensor resolution and diffraction HERE you’ll soon identify the same concept.

The upshot of it all is that “X” level of internal system vibration has a greater effect on a higher resolution sensor than it does on a lower resolution sensor.

Now what’s all this got to with shutter speed I hear you ask.  Well, whereas 1/focal length used to work pretty well back in the day, we need to advance the theory a little.

Let’s look at four shots from a Nikon D3, shot with a 300mm f2.8, mounted on a tripod and activated by a remote (so no finger-jabbing on the shutter button to effect the images).

Also please note that the lens is MANUALLY FOCUSED just once, so is sharply on the same place for all 4 shots.

These images are full resolution crops, I strongly recommend that you click on all four images to open them in new tabs and view them sequentially.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

Shutter = 1/1x (1/320th) Focal Length. No VR, No MLU (Mirror Lock Up). Camera on Tripod+remote release.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

Shutter = 1/2x (1/640th) Focal length. No VR. No MLU. Camera on Tripod+remote release.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

Shutter = 1/2x Focal length + VR. No MLU. Camera on Tripod+remote release.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

Shutter = 1/2x Focal length. Camera on Tripod+remote release + MLU – NO VR + Sandbag.

Now the thing is, the first shot at 1/320th looks crap because it’s riddled with system vibration – mainly a result of what’s termed ‘mirror slap’.  These vibrations travel up the lens barrel and are then reflected back by the front of the lens.  You basically end up with a packet of vibrations running up and down the lens barrel until they eventually die out.

These vibrations in effect make the sensor and the image being projected onto it ‘buzz, shimmy and shake’ – thus we get a fuzzy image; and all the fuzziness is down to internal system vibration.

We would actually have got a sharper shot hand holding the lens – the act of hand holding kills the vibrations!

As you can see in shot 2 we get a big jump in vibration reduction just by cranking the shutter speed up to 2x focal length (actually 1/640th).

The shot would be even sharper at 3x or 4x, because the vibrations are of a set frequency and thus speed of travel, and the faster the shutter speed we use the sooner we can get the exposure over and done with before the vibrations have any effect on the image.

We can employ ‘mirror up shooting’ as a technique to combat these vibrations; by lifting the mirror and then pausing to give the vibrations time to decay; and we could engage the lens VR too, as with the 3rd shot.  Collectively there has been another significant jump in overall sharpness of shot 3; though frankly the VR contribution is minimal.

I’m not a very big fan of VR !

In shot 4 you might get some idea why I’m no fan of VR.  Everything is the same as shot 3 except that the VR is OFF, and we’ve added a 3lb sandbag on top of the lens.  This does the same job as hand holding the lens – it kills the vibrations stone dead.

When you are shooting landscapes with much longer exposures/shutter speeds THE ONLY way to work is tripod plus mirror up shooting AND if you can stand to carry the weight, a good heavy sand bag!

Shot 4 would have been just as sharp if the shutter had been open for 20 seconds, just as long as there was no movement at all in the subject AND there was no ground vibration from a passing heavy goods train (there’s a rail track between the camera and the subject!).

For general tripod shooting of fairly static subjects I was always confident of sharp shots on the D3 (12Mb) at 2x focal length.

But since moving to a 16Mp D4 I’ve now found that sometimes this let’s me down, and that 2.5x focal length is a safer minimum to use.

But that’s nothing compared to what some medium format shooters have told me; where they can still detect the effects of vibration on super high resolution backs such as the IQ180 etc at as much as 5x focal length – and that’s with wide angle landscape style lenses!

So, overall my advice is to ALWAYS push for the highest shutter speed you can possibly obtain from the lighting conditions available.

Where this isn’t possible you really do need to perfect the skill of hand holding – once mastered you’ll be amazed at just how slow a shutter speed you can use WITHOUT employing the VR system (VR/IS often causes far more problems than it would apparently solve).

For long lens shooters the technique of killing vibration at low shutter speeds when the gear is mounted on a tripod is CRITICAL, because without it, the images will suffer just because of the tripod!

The remedy is simple – it’s what your left arm is for.

So, to recap:

  • If you shot without a tripod, the physical act of hand holding – properly – has a tendency to negate internal system vibrations caused by mirror slap etc just because your physical mass is in direct contact with the camera and lens, and so “damps” the vibrations.
  • If you shoot without a tripod you need to ensure that you are using a shutter speed fast enough to negate camera shake.
  • If you shoot without a tripod you need to ensure that you are using a shutter speed fast enough to FREEZE the action/movement of your subject.

 

Camera Shake and STUPID VR!

Now I’m going to have to say at the outset that this is only my opinion, and that this is pointed at Nikons VR system, and I don’t strictly know if Canons IS system works on the same math.

And this is not relevant to sensor-based stabilization, only the ‘in the lens’ type of VR.

The mechanics of how it works are somewhat irrelevant, but what is important is its working methodology.

Nikon VR works at a frequency of 1000Hz.

What is a “hertz”?  Well 1Hz = 1 full frequency cycle per second.  So 1000Hz = 1000 cycles per second, and each cycle is 1/1000th sec in duration.

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

Full cycle sine wave showing 1,0.5 & 0.25 cycles.

Now then, here’s the thing.  The VR unit is measuring the angular momentum of the lens movement at a rate of 1000 times per second. So in other words it is “sampling” movement every 1/1000th of a second and attempting to compensate for that movement.

But Nyquist-Shannon sampling theory – if you’re up for some mind-warping click HERE – says that effective sampling can only be achieved at half the working frequency – 500 cycles per second.

What is the time duration of one cycle at a frequency of 500Hz?  That’s right – 1/500th sec.

So basically, for normal photography, VR ceases to be of any real use at any shutter speed faster than 1/500th.

Remember shot 3 with the 300mm f2.8 earlier – I said the VR contribution at 1/640th was minimal?  Now you know why I said it!

Looking again at the frequency diagram above, we may get a fairly useful sample at 1/4 working frequency – 1/250th sec; but other than that my personal feelings about VR is that it’s junk – under normal circumstances it should be turned OFF.

What circumstances do I class as abnormal? Sitting on the floor of a heli doing ariel shots out of the open door springs to mind.

If you are working in an environment where something is vibrating YOU while you hand hold the camera then VR comes into its own.

But if it’s YOU doing the vibrating/shaking then it’s not going to help you very much in reality.

Yes, it looks good when you try it in the shop, and the sales twat tells you it’ll buy you three extra stops in shutter speed so now you can get shake-free shots at 1/10th of a second.

But unless you are photographing an anaesthetized Sloth or a statue, that 1/10th sec shutter speed is about as much use to you as a hole in the head. VR/IS only stabilizes the lens image – it doesn’t freeze time and stop a bird from flapping its wings, or indeed a brides veil from billowing in the breeze.

Don’t get me wrong; I’m not saying VR/IS is a total waste of time in ALL circumstances.  But I am saying that it’s a tool that should only be deployed when you need it, and YOU need to understand WHEN that time is; AND you need to be aware that it can cause major image problems if you use it in the wrong situation.

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In Conclusion

shutter speed,Red Kite,Andy Astbury,action photography,Wildlife in Pixels,vibration reduction,camera shake,mirror slap,sharp images

1/2000th sec is sufficient to pretty much freeze the forward motion of this eagle, but not the downward motion of the primary feathers.

This rather crappy shot of a White-tailed eagle might give you food for thought, especially if compared with the Red Kite at the start of the post.

The primary feathers are soft because we’ve run out of depth of field.  But, notice the motion blur on them too?  Even though 1/2000th sec in conjunction with a good panning technique is ample to freeze the forward motion of the bird, that same 1/2000th sec is NOT fast enough to freeze the speed of the descending primary feathers on the end of that 4 foot lever called a wing.

Even though your subject as a whole might be still for 1/60th sec or longer, unless it’s dead, some small part of it will move.  The larger the subject is in the frame then more apparent that movement will be.

Getting good sharp shots without motion blur in part of the subject, or camera shake and system vibration screwing up the entire image is easy; as long as you understand the basics – and your best tool to help you on your way is SHUTTER SPEED.

A tack sharp shot without blur but full of high iso noise is vastly superior to a noiseless shot full of blur and vibration artefacting.

Unless it’s done deliberately of course – “H-arty Farty” as my mate Ole Martin Dahle calls it!

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Metering Modes Explained

Camera Metering Modes

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I always get asked about which camera metering mode I use,  and to be honest, I think sometimes the folk doing the asking just can’t get their heads around my simplistic, and sometimes quite brutal answers!

“Andy, it’s got to be more complicated than that surely….otherwise why does the camera give me so many options…?”

Well, I always like to keep things really simple, mainly because I’m not the brightest diamond in the jewellery shop, and because I’m getting old and most often times my memory keeps buggering off on holiday without telling me!

But before I espouse on “metering the Uncle Andy way” let’s take a quick look at exactly how the usual metering options work and their effects on exposure.

The Metering Modes

  • Average (a setting usually buried in the center-weighted menu)
  • Spot
  • Center-weighted
  • 3D Matrix (Nikon) or Evaluative (Canon)
Metering Mode Icons

Metering Mode Icons

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Nikon D4S

The new Nikon D4S announced today

 

Nikon D4S left & D4 right

Nikon D4S left & D4 right

Well, that’s about right, my sexy Nikon D4 is officially out of date, and thanks to the Nikon D4S I’ve just lost a grand off the resale value of my camera – cheers chaps…..

Is Uncle Andy stressed at all about being kitted out with yesterdays gear?

Nope, not really.

So what’s new on the Nikon D4S ?

  • Well there’s been a few ergonomic tweaks which basically mean nothing for starters.
  • Seemingly dispelled are the rumours that it would have a higher Mp count – apparently this stays the same at 16.2Mp.
  • I was expecting some major change in AF but no, they’ve kept the venerable Multi-Cam 3500FX system.
  • New sensor design.
  • BUT – they’ve changed the image processor to Expeed 4 from Expeed 3.
  • AND – they’ve changed the battery from EN-EL18 to an EN-EL18a.

Bare in mind all I’m going on is the web – perish the thought that Nikon would ever think my opinion worthy of note and ACTUALLY SEND ME ONE.

Other changes:

  • A new Group Area AF mode – which from my own photography PoV is fairly meaningless, seeing as we already have 9 point dynamic AF – I can’t see it’ll make much difference. Plus, the Group AF mode always focusses on the nearest point – something you rarely want the camera to do!
  • 6 possible white balance presets as opposed to 3 on the D4 – I jam all my cameras into Cloudy B1 custom WB and leave them there – so this improvement isn’t worth jumping up and down about either.
  • Fairly gimmicky S Raw
  • Spot White Balance

On the storage front most reports say that the D4S carries over the D4 crazy arrangement of 1x CF plus 1x XQD.

My Basic Thoughts:

New Sensor – well the benefits can’t been seen by yours truly until I see a few RAW files from it – preferably taken by myself.

I’m glad they’ve kept it to 16.2Mp – if you crunch the numbers this is the optimum Mp count for an FX sensor – as Canon worked out aeons ago with the 1DsMk2; but then joined the stupid Mp race.

Image Processor changes – well, it’s reportedly 30% faster than the Expeed 3, which basically means that the D4S fires off images to storage 30% faster.

Now I can go out with the D4 and shoot getting on for 100 uncompressed 14bit RAW files in one continuous burst at 8 or 9 fps – do I want to chew through my storage any faster?  NO!

The Expeed 4 gives better high ISO performance?

Well perhaps it does, but I look at it this way.  If light is so damn low that you need to shoot at crackpot ISO numbers then you can say one thing – the light is crap.

If the light is crap then the image will look like crap – it’s just that with the Expeed 4 it’ll be slightly less noisy crap.

If I can pull 1/8000th sec at f7 or f8 at 3200ISO in half descent looking light using a D4 – which I do regularly – then why do I need a higher ISO capability?

The Red Squidger images you’ve seen in the previous blog articles are all 2000ISO and there is ZERO noise degradation – so again, why do I need more ISO capability.

Now if I was a ‘jobbing’ photo-jounalist, or I was embedded with the troops in Afghanistan or something of that ilk then I’d perhaps have a much different attitude.

But I’m not, and from my own perspective of wildlife & natural history photography these changes are of little interest to me – especially when they have a £5k price tag.

Battery Changes

There was always a persistent gripe about the battery life of the D4 EN-EL18 power cell – well, I’ve got two of them and have had no problems AT ALL with batteries running low.

I was REALLY annoyed that they switched from EN-EL4A D2/D3 style batteries – I’d got a handful of those already, and now when I go to Norway in June I’ve got to take 2 bloody chargers with me: yes the venerable D3 will be getting a summer holiday this year as second camera.

So, for me at least, the increased battery life of the new Nikon D4S 18a batteries is somewhat inconsequential – why do I want a battery that lasts longer than ‘for ever’ ??

Other Changes/Additions

I can’t see anything that excites me:  spot white balance?  Go and buy a Colour Checker Passport and do the job right – and that doesn’t cost £5k either (though they are a bit pricey).

Group Area AF – do me a favour (see above).

6 White Balance presets – what’s the point?

All of the above could be given away by Nikon as a firmware update for the D4 if they fancied being generous!

What I Would Have Got Excited About.

Twin UDMA 7 CF card slots and an XQD slot for dedicated video recording.

An improved AF module.

The ability to select ‘matched pairs’ of sensors – Canon offered this years ago and it was brilliant.

Internally recorded FX video of EXACTLY the same quality as that of a Canon 5D3, or at least the same quality as internal 1080p CROP.

AF mode selector back WHERE IT SHOULD BE!

Me being put in charge at Nikon!

In Conclusion

Do I want to buy one (even if I had the dough) – NO!

Do I wish I could afford one – NO!

Would I swap my D4 for a D4s – well of course I would.

Seriously though, I can just see an awful lot of people getting “hot under the collar” and stressing over this latest incarnation of this pro body from Nikon; but seriously, if you are then you need to just take a quiet step back and think about things calmly.

There is nothing – IMHO of course – on the D4S that warrants upgrading from the D4 – unless you have a penchant for spending your money that is.

But if you are still on a D3 or something older, and were thinking about buying a D4 – then hold off a while until the D4S in available; it’s makes better fiscal sense.

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Auto Focus & Shooting Speed

Auto Focus & Shooting Speed

Firstly, an apology to my blog followers for the weird blog post notification this morning – I had one of those “senior moments” where I confused the Preview button with Publish – DOH!

There is truly no hope………..!  But let’s get on….

The effectiveness of auto focus and its ability to track and follow a moving subject IS INFLUENCED by frame rate.

Why is this I here you ask.

Well, it’s simple, and logical if you think about it – where are your AF sensors?

They’re in the bottom of your cameras mirror box.

Most folk thing that the mirror just sits there, reflecting at 45 degrees all the light that comes through the lens up to the focus screen and viewfinder.  The fact that the mirror is still DOWN when they are using the auto focus leads most people into thinking the AF sensor array is elsewhere – that’s if they can be bothered to think about it in the first place.

 

So how does the AF array SEE the scene?

Because the center area of the main mirror is only SEMI silvered, and in reality light from the lens does actually pass through it.

 

auto focus,how auto focus works,main mirror,dslr mirror,mirror box,photography,camera

Main mirror of a Nikon D2Xs in the down position.

 

Now I don’t recommend you jam a ball point pen under your own main mirror, but in the next image:

 

auto focus,how auto focus works,main mirror,dslr mirror,mirror box,photography,camera

Main mirror of a Nikon D2Xs lifted so you can see the secondary mirror.

 

Now there’s a really good diagram of the mechanics at http://www.reikan.co.uk/ – makers of FoCal software, and I’ll perhaps get my goolies cut of for linking to it, but here it is:

 

This image belongs to Reikan

 

As you can now hopefully understand, light passes through the mirror and is reflected downwards by the secondary mirror into the AF sensor array.

As long as the mirror is DOWN the auto focus sensor array can see – and so do its job.

Unless the MAIN mirror is fully down, the secondary mirror is not in the correct position to send light to the auto focus sensor array – SO GUESS WHAT – that’s right, your AF ain’t working; or at least it’s just guessing.

So how do we go about giving the main mirror more “down time”?  Simply by slowing the frame rate down is how!

When I’m shooting wildlife using a continuous auto focus mode then I tend to shot at  5 frames per second in Continuous LOW (Nikon-speak) and have the Continuous HIGH setting in reserve set for 9 frames per second.

 

The Scenario Forces Auto Focus Settings Choices

From a photography perspective we are mainly concerned with subjects CROSSING or subjects CLOSING our camera position.

Once focus is acquired on a CROSSING subject (one that’s not changing its distance from the camera) then I might elect to use a faster frame rate as mirror-down-time isn’t so critical.

But subjects that are either CLOSING or CROSSING & CLOSING are far more common; and head on CLOSING subjects are the ones that give our auto focus systems the hardest workout – and show the system failures and short-comings the most.

Consider the focus scale on any lens you happen to have handy – as you focus closer to you the scale divisions get further apart; in other words the lens focus unit has to move further to change from say 10 meters to 5 meters than it does to move from 15 meters to 10 meters – it’s a non-linear scale of change.

So the closer a subject comes to your camera position the greater is the need for the auto focus sensors to see the subject AND react to its changed position – and yes, by the time it’s acquired focus and is ready to take the next frame the subject is now even closer – and things get very messy!

That’s why high grade dSLR auto focus systems have ‘predictive algorithms’ built into them.

Also. the amount of light on the scene AND the contrast between subject and background ALL effect the ability of the auto focus to do its job.  Even though most pro-summer and all pro body systems use phase detection auto focus, contrast between the subject to be tracked and its background does impact the efficiency of the overall system.

A swan against a dark background is a lot easier on the auto focus system than a panther in the jungle or a white-tailed eagle against a towering granite cliff in Norway, but the AF system in most cameras is perfectly capable of acquiring, locking on and tracking any of the above subjects.

So as a basic rule of thumb the more CLOSING a subject is then the LOWER your frame rate needs to be if you are looking for a sharp sequence of shots.  Conversely the more CROSSING a subject is then the higher the frame rate can be and you might still get away with it.

 

Points to Clarify

The mechanical actions of an exposure are:

  1. Mirror lifts
  2. Front shutter curtain falls
  3. Rear shutter curtain falls
  4. Mirror falls closed (down)

Here’s the thing; the individual time taken for each of these actions is the same ALL the time – irrespective of whether the shutter speed is 1/8000th sec or 8 sec; it’s the gap in between 2. & 3. that makes the difference.

And it’s the ONLY thing shutter-related we’ve got any control over.

So one full exposure takes t1 + t2 + shutter speed + t3 +t4, and the gap between t4 and the repeat of t1 on the next frame is what gives us our mirror down time between shots for any given frame rate.  So it’s this time gap between t4 and the repeat of t1 that we lengthen by dropping the shooting speed frame rate.

There’s another problem with using 10 or 11 frames per second with Nikon D3/D4 bodies.

10 fps on a D3 LOCKS the exposure to the values/settings of the first frame in the burst.

11 fps on a D3 LOCKS both exposure AND auto focus to the values/settings of the first frame in the burst.

11 fps on a D4 LOCKS both exposure AND auto focus* to those of the first frame in the burst – and it’s one heck of a burst to shoot where all the shots can be out of focus (and badly exposed) except the first one!

*Page 112 of the D4 manual says that at 11fps the second and subsequent shots in a burst may not be in focus or exposed correctly.

That’s Nikon-speak for “If you are photographing a statue or a parked car ALL your shots will be sharp and exposed the same; but don’t try shooting anything that’s getting closer to the camera, and don’t try shooting things where the frame exposure value changes”.

 

There’s a really cool video of 11 fps slowed right down with 5000fps slo-mo  HERE  but for Christ’ sake turn your volume down because the ST is some Marlene Dietrich wannabe!

So if you want to shoot action sequences that are sharp from the first frame to the last then remember – DON’T be greedy – SLOW DOWN!

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Flash Photography

Flash Photography

 

Red Squirrel,Andy Astbury,Flash,flash photography,fill flash,photography techniques

Really Cute Red Squirrel

 

On Sunday myself and my buddy Mark Davies made a short foray up to the Lake District and our small Red Squirrel site.  The weather was horrible, sleet, sun. rain, cloudy, sunny then rain again – in other words just not conducive to a half-descent session on the D4.

The one Achilles Heal with this site is the fact that it’s hard to get a descent background for your shots – it’s in the middle of a small wooded valley and you just can’t get away from tree trunks in the background.

This is further complicated by the fact that the “Squidgers” have a propensity for keeping in the ‘not so sunny’ bits, so frequently you end up with a scenario where backgrounds are brighter than foregrounds – which just won’t DO!

So what’s needed is some way to switch the lighting balance around to give a brighter foreground/subject AND a darker background.

Now that sounds all very well BUT; how do we achieve it?

Reflectors perhaps?  They’d do the trick but have one big problem; they rely on AMBIENT light  – and in the conditions we were shooting in the other day the value of the ambient light was up and down like a Yo-Yo.

Wouldn’t it be cool if we could have a consistent level of subject/foreground illumination AND at the same time have some degree of control over the exposure of the background?

Well with flash we can do just that!

Let’s look at a shot without flash:

 

No FLASH

No FLASH, AMBIENT light only – 1/320th @ f7.1

 

I don’t suppose this shot is too bad because the background isn’t strongly lit by the sun (it’s gone behind a cloud again!) but the foreground and background are pretty much the same exposure-wise.  For me there is not enough tonal separation between the two areas of the image, and the lighting is a bit flat.

If we could knock a stop or so out of the background; under expose it, then the image would have more tonal separation between foreground and background, and would look a lot better, but of course if we’re just working with ambient light then our adjusted exposure would under expose the foreground as well, so we’d be no better off.

Now look at the next image – we’ve got a background that’s under exposed by around  -1.5Ev, but the subject and foreground are lit pretty much to the same degree as before, and we’ve got a little more shape and form to the squirrel itself – it’s not quite so flat-looking.

 

With FLASH

With FLASH added – 1/800th @ f7.1

 

The image also has the slight sense that it’s been shot in more sunny conditions – which I can promise you it wasn’t !

And both images are basically straight off the camera, just with my neutral camera profile applied to them on import.

 

The Set Up

The Setup - shocking iPhone 3 quality!

The Setup – shocking iPhone 3 quality!

 

The first secret to good looking flash photography OF ANY KIND is to get the damn flash OFF the camera.

If we were in a totally dark studio with the sexiest looking model on the planet we’d NOT be lighting her with one light from the camera position now would we?

So we use basic studio lighting layouts where ever we can.

There are two other things to consider too:

  •   It’s broad daylight, so our exposure will contain both FLASH and an element of AMBIENT light – so we are working along the premise of ADDING to what’s already there.
  •   If we put the flash closer to the subject (off camera) then the output energy has less distance to travel in order to do its job – so it doesn’t have to have as much power behind it as it would have if emanating from the camera position.

 

You can see in the horrible iPhone 3 shot I took of the setup that I’m using two flash guns with white Lambency diffusers on them; one on a stand to the left and slightly in front of the log where the squirrels will sit, and one placed on the set base (Mr. Davies old knackered Black & Decker Workmate!) slightly behind the log and about the same distance away from where I anticipate a squirrel will sit on the log as the left flash.

The thing to note here is that I’m using the SIDE output of these Lambency diffuser domes and NOT the front – that’s why they are pointed up at the sky. The side output of these diffusers is very soft – just what the flash photography doctor ordered in terms of ‘keeping it real’.

The left light is going to be my MAIN light, the right is my FILL light.

The sun, when & if it decides to pop its head out, will be behind me and to my left so I place my MAIN light in a position where it will ‘simulate’ said ball in the sky.

The FILL light basically exists to ‘counter balance’ the ‘directionality’ of the MAIN light, and to weaken any shadows thrown by the MAIN light.

Does this flash bother a subject? For the most part NOT SO YOU’D NOTICE!

Take a look at the shot below – the caption will be relevant shortly.

This SB800 has just fired in "front curtain synch" and the balance of the exposure is from the ambient light - the shutter is still open after the flash has died. Does the squirrel look bothered?

This SB800 has just fired in “front curtain synch” and the balance of the exposure is from the ambient light. Does the squirrel look bothered?

Settings & The Black Art!

Before we talk about anything else I need to address the shutter curtain synch question.

We have two curtain synch options, FRONT & REAR.

Front Curtain (as in the shot above) – this means that the flash will fire as the front curtain starts to move, and most likely, the flash will be finished long before the rear curtain closes. If your subject reacts to the flash then some element of subject movement might be present in the shot due to the ambient light part of the exposure.

Rear Curtain Synch – my recommended ‘modus operandi’ – the ‘ambient only’ part of the exposure gets done first, then the flash fires as the rear curtain begins to close the exposure. This way, if the subject reacts to the flash the exposure will be over before it has chance to – MOSTLY!

The framing I want, and the depth of field I want dictates my camera position and aperture – in this case f7 or f8 – actually f7.1 is what I went for.

 

I elect to go with 2000 iso on the D4.

So now my only variable is shutter speed.

Ambient light dictates that to be 1/320th on average, and I want to UNDER EXPOSE that background by at least a stop and a bit (technical terms indeed!) so I elect to use a shutter speed of 1/800th.

So that’s it – I’m done; seeing as the light from the flashes will be constant my foreground/subject will ALWAYS be exposed correctly. In rear curtain synch I’ll negate the risk of subject movement ‘ghosting’ in the image, and at 1/800th I’ll have a far better chance of eliminating motion blur caused by a squirrel chewing food or twitching its whiskers etc.

 

Triggering Off-Camera Flashes

 

We can fire off-camera flashes in a number of ways, but distance, wet ground, occasional rain and squirrels with a propensity for chewing everything they see means CORDS ain’t one of ’em!

With the Nikon system that I obviously use we could employ another flash on-camera in MASTER/COMMANDER mode, with the flash pulse deactivated; or a dedicated commander such as the SU800; or if your camera has one, the built-in flash if it has a commander mode in the menu.

The one problem with Nikon CLS triggering system, and Canons as far as I know, is the reliance upon infra-red as the communication band. This is prone to a degree of unreliability in what we might term ‘dodgy’ conditions outdoors.

I use a Pocket Wizard MiniTT1 atop the camera and a FlexTT5 under my main light. The beauty of this system is that the comms is RADIO – far more reliable outdoors than IR.

Because a. I’m poor and can’t afford another TT5, and b. the proximity of my MAIN and FILL light, I put the SB800 FILL light in SU mode so it gets triggered by the flash from the MAIN light.

What I wouldn’t give for a dozen Nikon SB901’s and 12 TT5s – I’d kill for them!

The MAIN light itself is in TTL FP mode.

The beauty of this setup is that the MAIN light ‘thinks’ the TT5 is a camera, and the camera ‘thinks’ the miniTTL is a flash gun, so I have direct communication between camera and flash of iso and aperture information.

Also, I can turn the flash output down by up to -3Ev using the flash exposure compensation button without it having an effect on the background ambient exposure.

Don’t forget, seeing as my exposure is always going to 1/800th @ f7.1 at 2000 iso the CAMERA is in MANUAL exposure mode. So as long as the two flashes output enough light to expose the subject correctly at those settings (which they always will until the batteries die!) I basically can’t go wrong.

When shooting like this I also have a major leaning towards shooting in single servo – one shot at a time with just one AF point active.

 

Flash Photography – Flash Duration or Burn Time

Now here’s what you need to get your head around. As you vary the output of a flash like the SB800 the DURATION of the flash or BURN TIME of the tube changes

Below are the quoted figures for the Nikon SB800, burn time/output:

1/1050 sec. at M1/1 (full) output
1/1100 sec. at M1/2 output
1/2700 sec. at M1/4 output
1/5900 sec. at M1/8 output
1/10900 sec. at M1/16 output
1/17800 sec. at M1/32 output
1/32300 sec. at M1/64 output
1/41600 sec. at M1/128 output

On top of that there’s something else we need to take into account – and this goes for Canon shooters too; though Canon terminology is different.

Shutter Speed & The FP Option

35mm format cameras all have a falling curtain shutter with two curtains, a front one, and a rear one.

As your press the shutter button the FRONT curtain starts to fall, then the rear curtain starts to chase after it, the two meet at the bottom of the shutter plane and the exposure is over.

The LONGER or slower the shutter speed the greater head-start the front curtain has!

At speeds of 1/250th and slower the front curtain has reached the end of its travel BEFORE the rear curtain wakes up and decides to move – in other words THE SENSOR is FULLY exposed.

The fastest shutter speed that results in a FULLY EXPOSED film plane/sensor is the basic camera-to-flash synch speed; X synch as it used to be called, and when I started learning about photography this was usually 1/60th; and on some really crap cameras it was 1/30th!

But with modern technology and light weight materials these curtains can now get moving a lot faster, so basic synch now runs at 1/250th for a full frame DSLR.

If you go into your flash camera menu you’ll find an AUTO FP setting for Nikon, Canon refer to this as HSS or High Speed Synch – which makes far more sense (Nikon please take note, Canon got something right so please replicate!).

There’s something of an argument as to whether FP stands for Focal Plane or Flash Pulse; and frankly both are applicable, but it means the same as Canon’s HSS or High Speed Synch.

At speeds above/faster than 1/250th the sensor/film plane is NOT fully exposed. The gap between the front and rear curtains forms a slot or ‘letter box’ that travels downwards across the face of the sensor, so the image is, if you like, ‘scanned’ onto the imaging plane.

Obviously this is going to cause on heck of an exposure problem if the flash output is ‘dumped’ as a single pulse.

So FP/HSS mode physically pulses or strobes the flash output to the point where it behaves like a continuous light source.

If the flash was to fire with a single pulse then the ‘letterbox slot’ would receive the flash exposure, but you’d end up with bands of under exposure at the bottom or top of the image depending on the curtain synch mode – front or rear.

In FP/HSS mode the power output of each individual pulse in the sequence will drop as the shutter speed shortens, so even though you might have 1:1 power selected on the back of the flash itself (which I usually do on the MAIN light, and 1/2 on the FILL light) the pulses of light will be of lower power, but their cumulative effect gives the desired result.

By reviewing the shot on the back of the camera we can compensate for changes in ambient in the entire scene (we might want to dilute the effect of the main light somewhat if the sun suddenly breaks out on the subject as well as the background) by raising the shutter speed a little – or we might want to lighten the shot globally by lowering the shutter speed if it suddenly goes very gloomy.

We might want to change the balance between ambient and flash; this again can be done from the camera with the flash exposure compensation controls; or if needs be, by physically getting up and moving the flash units are little nearer or further away from the subject.

All in all, using flash is really easy, and always has been.

Except nowadays manufacturers tend to put far more controls and modes on things then are really necessary; the upshot of which is to frighten the uninitiated and then confuse them even further with instruction manuals that appear to be written by someone under the influence of Class A drugs!

 

"Trouble Brewing.." Confrontation over the right to feed between two Red Squirrels.

“Trouble Brewing..” Confrontation over the right to feed between two Red Squirrels.

 

The whole idea of flash is that it should do its job but leave no obvious trace to the viewer.

But its benefits to you as the photographer are invaluable – higher shutter speeds, more depth of field and better isolation of the subject from its background are the three main ones that you need to be taking advantage of right now.

If you have the gear and don’t understand how to use it then why not book a tuition day with me – then perhaps I could afford some more TT5s!

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Paper White – Desktop Printing 101

Paper White video

A while back I posted an article called How White is Paper White

As a follow-up to my last post on the basic properties of printing paper media I thought I’d post this video to refresh the idea of “white”.

In this video we basically look at a range of 10 Permajet papers and simply compare their tints and brightness – it’s an illustration I give at my print workshops which never fails to amaze all the attendees.

I know I keep ‘banging on’ about this but you must understand:

  • Very few paper whites are even close to being neutral.
  • No paper is WHITE in terms of luminosity – RGB 255 in 8 bit colour terms.
  • No paper can hold a true black – RGB 0 in 8 bit colour terms.

In real-world terms ALL printing paper is a TINTED GREY – some cool, some warm.

printing,paper white,desktop printing,Andy Astbury,Wildlife in Pixels

If we attempted to print the image above on a cool tinted paper then we would REDUCE or even CANCEL OUT the warm tonal effects and general ‘atmosphere’ of the image.

Conversely, print it to a warmer tinted ‘paper white’ and the atmosphere would be enhanced.

Would this enhancement be a good thing?  Well, er NO – not if we were happy with our original ‘on screen’ processing.

You need to look upon ‘paper white’ as another TOOL to help you achieve your goal of great looking photographs, with a minimum of fuss and effort on your part.

We have to ‘soft proof’ our images if we want to get a print off the printer that matches what we see on our monitor.

But we can’t soft proof until we have made a decision about what paper we are going to soft-proof to.

Choosing a paper who’s characteristics match our finished ‘on screen’ image in terms of TINT especially, will make the job of soft proofing much easier.

How, why?

Proper soft proofing requires us to make a copy of our original image (there’s most peoples first mistake – not making a copy) and then making adjustments to said copy, in a soft proof environment, so that it it renders correctly on the print – in other words it matches our original processed image.

Printing from Photoshop requires a hard copy, printing from Lightroom is different – it relies on VIRTUAL copies.

Either way, this copy and its proof adjustments are what get sent to the printer along what we call the PRINT PIPELINE.

The print pipeline has to do a lot of work:

  • It has to transpose our adjusted/soft proofed image colour values from additive RGB to print CMYK
  • It has to up sample or interpolate the image dpi instructions to the print head, depending on print output size.
  • It has to apply the correct droplet size instructions to each nozzle in the print head hundreds of times per second.
  • And it has to do a lot of other ‘stuff’ besides!!

The key component is the Printer Driver – and printer drivers are basically CRAP at carrying out all but the simplest of instructions.

In other words they don’t like hard work.

Printing to a paper white that matches our image:

  • Warm image to warm tint paper white
  • Cool image to cool paper white

will reduce to the amount of adjustments we have to make under soft proofing and therefore REDUCE the printer driver workload.

The less work the print driver has to do, the lower is the risk of things  ‘getting lost in translation‘ and if nothing gets lost then the print matches the on screen image – assuming of course that your eyes haven’t let you down at the soft proofing stage!

print,desktop printing,paper white

IMPORTANT – Click Image to Enlarge in new window

If we try to print this squirrel on the left to Permajet Gloss 271 (warmish image to very cool tint paper white) we can see what will happen.

We have got to make a couple of tweaks in terms on luminosity BUT we’ve also got to make a global change to the overall colour temperature of the image – this will most likely present us with a need for further  opposing colour channel adjustments between light and dark tones.

 

print,desktop printing,paper white

IMPORTANT – Click Image to Enlarge in new window

Whereas the same image sent to Permajet Fibre Base Gloss Warmtone all we’ll have to do is tweak the luminosity up a tiny bit and saturation down a couple of points and basically we’ll be sorted.

So less work, and less work means less room for error in our hardware drivers; this leads to more efficient printing and reduced print production costs.

And reduced cost leads to a happy photographer!

Printing images is EASY –  as long as you get all your ducks in a row – and you’ve only got a handful of ducks to control.

Understanding print media and grasping the implications of paper white is one of those ducks………

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