Image Retouching

Posted on May 11, 2015 by Andrew Astbury

Image Retouching in Photoshop CC 2014

It’s very rare that we ever get a frame from our camera that doesn’t need retouching – that’s a FACT.

Imperfections in the frame can be both ‘behind the shutter’ and ‘in front of the lens’ – sensor dust and crud on the subject. But you’ll take photographs where these imperfections are hard, if not impossible, to see under normal viewing.

But print that image BIG and those invisible faults will begin to be visually apparent; by which time it’s too bloomin’ late and they’ve cost you money; or worse still, a client.

The ‘visualise spots’ tool in Lightroom will show you a certain amount of ‘dust bunny’ type faults and errors, but the way Lightroom executes retouching repairs is not always ‘quite up to snuff’; and when it comes to dust, crap and other undesirables on the subject itself Lightroom will fail to recognise them in the first place.

Image retouching isn’t really all that difficult; but it can be an intensely tedious and time-consuming process.

To that end I’ve stuck these HD video lessons on my You Tube channel.

In these videos I illustrate how I deploy the Spot Healing brush, Healing Brush, Clone Tool, Patch Tool and Content Aware Fill command to carry out some basic image retouching on a shot of cutlery bright ware.

I demonstrate the addition of a ‘dust visibility’ curves adjustment layer – something that everyone should ‘get the hang’ of using – as a first step to effective image retouching.

When photographing glossy, high reflectivity subjects we need to remove the imperfections and smooth the surfaces of the subject without reducing the ‘glossiness’ and turning it matt!

Please note: a couple of these videos are in excess of 20 minutes duration and they will look better at full resolution HDV if you click the You Tube icon. Also, it takes a lot longer to do a job when you have to talk about at the same time!

I hope you get some idea as to how simple and straightforward my approach to image retouching is!

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Image Sharpness

Posted on April 16, 2015 by Andrew Astbury

Image Sharpness

I spent the other afternoon in the Big Tower at Gigrin, in the very pleasant company company of Mr. Jeffrey “Jeffer-Cakes” Young. Left arm feeling better yet Jeff?

I think I’m fairly safe in saying that once feeding time commenced at 3pm it didn’t take too long before Jeff got a firm understanding of just how damn hard bird flight photography truly is – if you are shooting for true image sharpness at 1:1 resolution.

I’d warned Jeff before-hand that his Canon 5Dmk3 would make his session somewhat more difficult than a 1Dx, due to it’s slightly less tractable autofocus adjustments. But that with his 300mm f2.8 – even with his 1.4x converter mounted, his equipment was easily up to the job at hand.

I on the other hand was back on the Nikon gear – my 200-400 f4; but using a D4S I’d borrowed from Paul Atkins for some real head-to-head testing against the D4 (there’s a barrow load of Astbury venom headed Nikon’s way shortly I can tell you….watch this space as they say).

Amongst the many topics discussed and pondered upon, I was trying to explain to Jeff the fundamental difference between ‘perceived’ and ‘real’ image sharpness.

Gigrin is a good place to find vast armies of ‘photographers’ who have ZERO CLUE that such an argument or difference even exists.

As a ‘teacher’ I can easily tell when I’m sharing hide space with folk like this because they develop quizzical frowns and slightly self-righteous smirks as they eavesdrop on the conversation between my client and I.

“THEY” don’t understand that my client is wanting to achieve the same goal as the one I’m always chasing after; and that that goal is as different from their goal as a fillet of oak-smoked Scottish salmon is from a tin of John West mush.

I suppose I’d better start explaining myself at this juncture; so below are two 800 pixel long edge jpeg files that you typically see posted on a nature photography forum, website or blog:

image sharpness, Andy Astbury, Wildlife in Pixels, Red Kite

IMAGE 1. Red Kite – Nikon D4S+200-400 f4 – CLICK IMAGE to view properly.

Click the images to view them properly.

IMAGE 2. Red Kite – Nikon D4S+200-400 f4 – CLICK IMAGE to view properly.

“THEY” would be equally as pleased with either…..!

Both images look pretty sharp, well exposed and have pretty darn good composition from an editorial point of view too – so we’re all golden aren’t we!

Or are we?

Both images would look equally as good in terms of image sharpness at 1200 pixels on the long edge, and because I’m a smart-arse I could easily print both images to A4 – and they’d still look as good as each other.

But, one of them would also readily print to A3+ and in its digital form would get accepted at almost any stock agency on the planet, but the other one would most emphatically NOT pass muster for either purpose.

That’s because one of them has real, true image sharpness, while the other has none; all it’s image sharpness is perceptual and artificially induced through image processing.

Guessed which is which yet?

IMAGE 1 at 1:1 native resolution – CLICK IMAGE to view properly.

Image 1. has true sharpness because it is IN FOCUS.

IMAGE 2 at 1:1 native resolution – CLICK IMAGE to view properly.

And you don’t need glasses to see that image 2 is simply OUT OF FOCUS.

The next question is; which image is the cropped one – number 2 ?

Wrong…it’s number 1…

Image 1 uncropped is 4928 pixels long edge, and cropped is 3565, in other words a 28% crop, which will yield a 15+ inch print without any trouble whatsoever.

Image 2 is NOT cropped – it has just been SHRUNK to around 16% of its original size in the Lightroom export utility with standard screen output sharpening. So you can make a ‘silk purse from a sows ear’ – and no one would be any the wiser, as long as they never saw anything approaching the full resolution image!

Given that both images were shot at 400mm focal length, it’s obvious that the bird in image 1 (now you know it’s cropped a bit) is FURTHER AWAY than the bird in image 2.

So why is one IN FOCUS and the other not?

The bird in image 1 is ‘crossing’ the frame more than it is ‘closing in’ on the camera.

The bird in image 2 is closer to the camera to begin with, and is getting closer by the millisecond.

These two scenarios impose totally different work-loads on the autofocus system.

The ability of the autofocus system to cope with ANY imposed work-load is totally dependent upon the control parameters you have set in the camera.

The ‘success’ rate of these adjustable autofocus parameter settings is effected by:

Changing spatial relationship between camera and subject during a burst of frames.
Subject-to-camera closing speed
Pre-shot tracking time.
Frame rate.

And a few more things besides…!

The autofocus workloads for images 1 & 2 are poles apart, but the control parameter settings are identical.

The Leucistic Red Kite in the shot below is chugging along at roughly the same speed as its non-leucistic cousin in image 2. It’s also at pretty much the same focus distance:

Image 3. Leucistic Red Kite – same distance, closing speed and focal length as image 2. CLICK IMAGE to view larger version.

So why is image 3 IN FOCUS when, given a similar scenario, image 2 is out of focus?

Because the autofocus control parameters are set differently – that’s why.

FACT: no single combination of autofocus control parameter settings will be your ‘magic bullet’ and give you nothing but sharp images with no ‘duds’ – unless you use a 12mm fish-eye lens that is!

Problems and focus errors INCREASE in frequency in direct proportion to increasing focal length.

They will also increase in frequency THE INSTANT you switch from a prime lens to a zoom lens, especially if the ‘zoom ratio’ exceeds 3:1.

Then we have to consider the accuracy and speed of the cameras autofocus system AND the speed of the lens autofocus motor – and sadly these criteria generally become more favourable with an increased price tag.

So if you’re using a Nikon D800 with an 80-400, or a Canon 70D with a 100-400 then there are going to be more than a few bumps in your road. And if you stick to just one set of autofocus control settings all the time then those bumps are going to turn into mountains – some of which are going to kill you off before you make their summit….metaphorically speaking of course!

And God forbid that you try this image 3 ‘head on close up’ malarkey with a Sigma 50-500 – if you want that level of shot quality then you might just as well stay at home and save yourself the hide fees and petrol money !

Things don’t get any easier if you do spend the ‘big bucks’ either.

Fast glass and a pro body ‘speed machine’ will offer you more control adjustments for sure. But that just means more chances to ‘screw things up’ unless you know EXACTLY how your autofocus system works, exactly what all those different controls actually DO, and you know how to relate those controls to what’s happening in front of you.

Whatever lens and camera body combination any of us use, we have to first of all find, then learn to work within it’s ‘effective envelope of operation’ – and by that I mean the REAL one, which is not necessarily always on a par with what the manufacturer might lead you to believe.

Take my Nikon 200-400 for example. If I used autofocus on a static subject, let alone a moving one, at much past 50 metres using the venerable old D3 body and 400mm focal length, things in the critical image sharpness department became somewhat sketchy to say the least. But put it on a D4 or D4S and I can shoot tack sharp focussing targets at 80 to 100 metres all day long……not that I make a habit of this most meaningless of photographic pastimes.

That discrepancy is due to the old D3 autofocus system lacking the ability to accurately discriminate between precise distances from infinity to much over 50 metres when that particular lens was being used. But swap the lens out for a 400 f2.8 prime and things were far better!

Using the lens on either a D4 or D4S on head-on fast moving/closing subjects such as Mr.Leucistic above, we hit another snag at 400mm – once the subject is less than 20 metres away the autofocus system can’t keep up and the image sharpness effectively drops off the proverbial cliff. But zoom out to 200mm and that ‘cut-off’ distance will reduce to 10 metres or so. Subjects closing at slower speeds can get much closer to the camera before sharp focus begins to fail.

As far as I’m concerned this problem is more to do with the speed of the autofocus motor inside the lens than anything else. Nikon brought out an updated version of this lens a few years back – amongst its ‘star qualities’ was a new nano-coating that stopped the lens from flaring. But does it focus any faster – does it heck! And my version doesn’t suffer from flare either….!

Getting to know your equipment and how it all works is critical if you want your photography to improve in terms of image sharpness.

Shameless Plug Number 1.

I keep mentioning it – my ebook on Canon & Nikon Autofocus with long glass.

Understanding Canon & Nikon Autofocus

for

Bird in Flight Photography

Click Image for details.

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View Autofocus Points in Lightroom

Posted on February 1, 2015 by Andrew Astbury

Mr. Malcolm Clayton sent me a link last week to a free plug-in for Lightroom that displays the autofocus points used for the shot, plus other very useful information such as focus distance, f-number and shutter speed, depth of field (DoF) values and other bits and bobs.

The plug-in is called “Show Focus Points” and you can download it HERE

Follow the installation instruction to the letter!

Once installed you can only launch it from the LIBRARY MODULE:

Accessing the Plug-in via the Library>Plug-in Extras menu CLICK to view LARGER

You will see this sort of thing:

The “Show Focus Points” for Lightroom plug-in window. CLICK to view LARGER.

It’s a usefull tool to have because short of running the rather clunky Canon DPP or Nikon ViewNX software it’s the easiest way of getting hold of autofocus information without sending the image to Photoshop and looking through the mind-numbing RAW schema data – something I do out of habbit!

It displays a ton of useful data about your camera focus settings and exposure, and the autofocus point used – be it set by you, or chosen by the camera.

As far as I can see, the plug-in only displays the main active autofocus point on Nikon D4 and D4S files, but all the autofocus group as well as active points seem to display when viewing .CR2 Canon files as we can see on this very impressive car number plate!:

Screen grab of an unprocessed 1Dx/200-400/TC shot I did while testing the tracking capabilities of the Canon lens with the TC active – the REAL image looks more impressive than this! I’m actually zooming out while tracking too – this is around 200mm + the 1.4x TC. CLICK to view LARGER

Canon 1Dx in AF Point Expansion 4 point; what I call "1 with 4 friends".

Canon 1Dx in AI Servo AF Point Expansion 4 point; what I call “1 with 4 friends”. CLICK to view LARGER.

Canon 1Dx in AI-F autofocus showing all autofocus points used be the camera.

Viewing your autofocus points is a very valid learning tool when trying to become familiar with your cameras autofocus, and it’s also handy if you want to see why and where you’ve “screwed the pooch” – hey, we ALL DO IT from time to time!

Useful tool to have IMO and it’s FREE – Andy likes free…

Cheers to Malc Clayton for bringing this to my attention.

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Autofocus Drill-down

Posted on January 31, 2015 by Andrew Astbury

Long Lens Autofocus Considerations.

If you read my previous post about the 1Dx sensor you will have seen that I mentioned my, as yet unfinished, tome about long lens autofocus for wildlife photography. It’s a frustrating project because I keep having to change various bits to make them simpler, re-order certain paragraphs etc.

But I thought I’d blog-post something here that I expand on in the project, and it’s something an awful lot of people NEVER take into consideration.

As a Nikon user I’m used to the vagaries of the Nikon AF system and I manage to work with it just fine – I have to!

But photographers who don’t shoot wildlife, and don’t use 400mm or 500mm lumps of glass as their “standard lens” might not find the vagaries I bitch about quite so apparent; indeed some might not come across them at all.

As a wildlife photographer I shoot in crappy light, I shoot with slow lenses (both in terms of f-number and focus speed), I shoot low contrast subjects on equally low contrast backgrounds, I’m constantly shooting brown-on-brown, grey on grey etc, I shoot stupidly small subjects….the list goes on!

For years, good wildlife photography has been done by pushing camera/lens capabilities beyond their performance design parameters; and this particularly applies to our “expectations” of our latest and greatest AF system – be it Canon or Nikon.

I find so many people who come to my workshops etc. are not even aware of this one simple fact – sharp focus requires more work AND increased speed of work by the lens AF motor the closer a subject is to the camera.

Just try looking at the delineations on the focusing ring of a lens:

Canon 200-400 focused at 20 meters. (Lens porn WARNING: This lens will cause movements in the front-of-trouser department).

Look at the scale and note the distance between 20m and 50m marks – that distance is indicative of the amount of work required of the autofocus controller and motor to move from 20m to 50m or vice versa.

Now look where the 10m mark is – it requires FAR MORE work from the focus controller and motor to move from 20m to 10m, than it did to move the 30 meters from 50m to 20m.

On top of that extra work, if we are tracking a subject moving at 10 meters per second the lens takes 3 seconds to move from 50m to 20m, but then has to move a lot FASTER as well to cover the extra workload moving from 20m to 10m in just 1 second.

Then you wonder why your Nikon D40 + Sigma 50-500mm is crap at doing “birds in flight”; you never realise that your autofocus system is bag of spanners and powered by a hamster on a wheel…….it’s just not fast enough kids

Autofocus accuracy is nothing without speed if you are wanting to do productive wildlife photography.

As I alluded to before, as a photographer of the old wildlife I, and YOU will always encounter problems that users in other photographic disciplines may not, or if they do then the problem has a lot less impact than it does for us.

Think of it this way – a sports photographer will use a 500mm f4 to photograph a 6 foot tall overpaid git who’s 25m to 70m away, on a sunny Saturday afternoon or under a squillion watts of flood lighting; and he’s looking for a 6×12 for the back page of the Sunday Sport. I’ll use the same lens to photograph a cute Red Squirrel at 5m to 7m in a gloomy wood in the middle of winter and I’m looking for a full size, full resolution image for stock.

Red Squirrel – this is basically the FURTHEST DISTANCE you could shoot at with a 500mm lens and still get a meaningful composition. Click for larger view.

Note the distance – 631/100 – that means 6.31 meters. Aperture is f8, so DoF is around 7 centimeters.

The image is UNCROPPED as are all the other images in this post

We don’t really want to be any further away because “his cuteness” will be too small in the frame:

The factors effecting subject distance choice are:

lens resolving power – small, fine details need to be as close as possible.*
sensor resolving power – we need as many pixels as possible covering the subject.*
auto focus point placement accuracy – if the subject is too small in the frame, point placement is inaccurate.
general “in camera” composition

*These two are inextricably intertwined

I’ve indicated the active focus point on the above image too because here’s a depth of field “point of note” – autofocus wastes DoF. Where is the plane of focus? Just between the eyes of the squirrel.

Assuming the accepted modern norm of DoF distribution – 50/50 – that’s 3.5 centimeters in front of the plane of focus, or indicted AF point, that will be sharp. Only problem there is that the squirrel’s nose is only around 1 centimeter closer to the camera than the AF point, so the remaining 2 .5 centimeters of DoF is wasted on a sharp rendition of the fresh air between its nose and the camera!!

Now let’s change camera orientation and go a bit closer to get the very TIGHTEST shot composition:

Red Squirrel – this is basically the CLOSEST DISTANCE you could shoot at with a 500mm lens and still get a meaningful composition. Click for larger view

The subject distance is 5.62 meters. Aperture is f6.3 so DoF is around 4.4 centimeters.

Now let’s change photographic hats and imagine we are a sports photographer and we are spending a Saturday afternoon photographing a bunch of over-paid 6 foot tall gits chasing a ball around a field, using the very same camera and lens:

He’s not over-paid or chasing a ball, but this is the CLOSEST distance we can shoot at with this orientation and still get a “not too tight” composition of a 6 foot git! “Shep’s” not a git really – well, not much! Click to enlarge

The distance for this shot is 29.9 meters. Aperture is f6.3 so DoF is around 1.34 meters.

And here we are at the CLOSEST distance for this horizontal camera orientation – still not too tight. Click to enlarge.

The distance here is 50.1 meters. Aperture is f6.3 so DoF is around 3.79 meters.

So with this new “sports shooter” hat on, have we got an easier job than the cold, wet squirrel photographer?

You bet your sweet life we have!

The “Shepster” can basically jump around and move about like an idiot on acid and stay in sharp focus because:

the depth of field at those distances is large.
more importantly, the autofocus has VERY little work to do along the lens axis, because 1 or 2 meters of subject movement closer to the camera requires very small movements of the lens focus mechanicals.

But the poor wildlife photographer with his cute squirrel has so much more of a hard time getting good sharp shots because:

he/she has got little or no depth of field
small subject movements along the lens axis require very large and very fast movement of the lens focus mechanicals.

So the next time you watch a video by Canon or Nikon demonstrating the effectiveness of their new AF system on some new camera body or other; or you go trawling the internet looking for what AF settings the pros use, just bear in mind that “one mans fruit may be another mans poison” just because he/she photographs bigger subjects at longer average distances”.

Equipment choice and its manner of deployment and use is just not a level playing field is it…but it’s something a lot of folk don’t realise or think about.

And how many folk would ever consider that a desired “in camera” image composition has such a massive set of implications for autofocus performance – not many – but if you put your brain in gear it’s blindingly obvious.

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Canon 1Dx Sensor Noise

Posted on January 30, 2015 by Andrew Astbury

What seems an age ago now I did a two-day workshop for Calumet at Drummond Street in London, and a chap turned up there armed with a Canon 1Dx PLUS a 200-400 f4. The lens had only just been launched, and he’d been out and spent a truck-load of cash on both lens and body.

Yours truly was all over him like a severe rash, and I ripped it from his poor old fingers, stuck it in Case 2 and dived outside and started ripping through frames of vehicles passing the store!

I was smitten from that very moment – but it was weird all the same. I was joyous at how the lens and camera performed; pissed off that I didn’t own it; and seething at Nikon AF and the poor distance performance of their own 200-400.

Not that Nikon is crap – far from it; it’s fantastic – but this was just SO much better, and child that I am, THIS was what I should be using and all else was just pants.

Begrudgingly I handed the old chap his camera back, satisfied my dour mood with a cursory “not bad….” and carried on with the workshop.

Later in the day I stuck the images I’d shot with the Canon 1Dx into Lightroom on the 27″ iMac I use for workshop presentations – and was immediately a little happier – they looked “iffy” to say the least!

The Nikon 200-400s’ distance resolution problem has always hacked me off – 10m or less it’s epic, but 75m and further I hate it, and in between well, sometimes I like it and sometimes I don’t. And it’s bad with teleconverters, it really is…

Scanning through all the Canon 1Dx shots I was still amazed by the lens – it was delivering tack sharp high-resolution images at all focal lengths and distances, with and without teleconverter; basically it was kicking the Nikon into the last century simply by NOT displaying ANY of the same faults.

But I was having to look past – in comparison to Nikon – a thin veil of sensor noise, and I was also aware of a reduction in sensor Dynamic Range when I looked at the shots and noted the popped highlights that experience told me my Nikon wouldn’t produce.

Since then I’ve had a few more occasional chances to use the lens and body, and my results have continued to generate the same response – great lens, shame about the sensor IQ; but I’ve always been using other folks cameras and you don’t like to mess about with them too much, so I have always assumed that things “could be made a bit better” with some fiddling about.

Last year, hand on heart, I can honestly say that I was responsible, in whole or part, for at least 6 sales of Canon 200-400’s to existing 1Dx owners, and the lens-envy has always been there when they’ve been and bought it.

Since the first day I handled the lens I’ve been of the mind that it would be the ultimate lens for my Eagle workshops in Norway. I was thinking of trying to take one, plus the required 1Dx, over there in June last year; but seeing as the my clients were all Nikon I thought I’d best not!

But I have a “mixed bag” of clients booked for my Winter trip in a couple of weeks time, so seeing as I was of the mind that a few folk owed me a few favours…..

Upshot is that for the last two weeks, thanks to Reece Piper at Calumet, I’ve had a Canon 1Dx sat in my office; and many thanks to my favourite Geordie lass June Lown, a 200-400 f4 to go with it.

When I picked up the 1Dx from Calumet I swiped a 100mm f2.8 macro while I was at it, as I had been tasked with a high speed action shot featuring makeup brushes and I thought we’d go nuts and do the shot whilst exploring the 1Dx in a bit more depth.

Canon 1Dx + 100mm f2.8 macro. Nikon SB800 flash & Calumet ProSeries wireless.

Prior to picking up the Canon 1Dx I’d done a few test shots on my own Nikon gear just to get the lighting and flash timing sorted out, but I’d been using some different brushes:

Okay, so here is the base .CR2 raw file for the finished image:

Base .CR2 raw file

Now, I’m going to get to the point of this post topic!

As a standard retouching procedure on this type of shot I always overlay a custom Curves Adjustment layer with a sine-wave curve – it helps show up all those little imperfections you can’t see when you view the image without it:

Custom Curve for retouching

The main purpose in this particular case is to check for dark imperfections in that black background – yep, proper retouching is all about the minutia if you want perfection.

I’m trying to put together a video course on retouching that’ll be available in my store a little later this year – email me for details

Because the powder velocity is so damned high as it leaves the brush bristles I needed 1/32nd output power on the SB800s in order to freeze absolutely every grain of powder, so the shots(both Nikon and Canon) were at 400 iso just to give me a working aperture of f14.

When checking the test shots they looked like this with the customised Curve Layer:

Nikon D4 400 ISO test shot with custom curves layer.

Nikon D4 400 ISO 1/250th @ f14 test shot with custom curves layer.

Check out how clean the black background is.

So now all we do is swap the brushes, and change from Nikon D4 to the Canon 1Dx – I make no changes to either the lights or the background, and the exposure settings are exactly the same – 1/250th, 400 ISO, f14 – and I’m expecting gold…

But throw the CR2 file into Photoshop and stick the custom curve over it to see the comparrison:

Canon 1Dx 400 ISO 1/250th @ f14

Sweet Jesus………….!

Now don’t run away with the idea that it’s the “normal” noise you think of – luminance noise. In fact from that point of view it’s no better or worse than the Nikon D4 sensor.

But what you can see here is PATTERN NOISE/READ NOISE – see my Sensor Noise post from a while ago HERE

Don’t get me wrong, you can barely see it at 100% magnification, and a lot of folk won’t notice it AT ALL:

Canon 1Dx/Nikon D4 comparrison at 100% magnification viewed normally.

Canon 1Dx/Nikon D4 comparison at 100% magnification viewed normally. CLICK to view larger

But if you want BIG prints, or you sell your images for stock, then you need to check them a lot more thoroughly at higher magnifications:

Comparison at 400% magnification CLICK to view larger

At 400% the noise is just about visible – because it’s a dark error/fault on a basically slightly darker background. But keep it at 100% and put the custom curve over it and:

Custome Curve layer at 100% - now that pattern noise on the Canon sensor is obvious.

Custom Curve layer at 100% – now that pattern noise on the Canon sensor is obvious.

…now you can see what you have got to take care off in retouching.

Got a 1Dx? Then this pattern noise is in YOUR images – FACT.

But if the image has a more “normal” tonality to it then it certainly won’t be obvious to you – but it’s there nevertheless. Just try looking in your shadow areas.

Why the 1Dx sensor should be so much noisier than the D4/D4S is beyond me to be honest. Yes I know it’s an older mark, but the then current Nikon D3 and D3S were far better than this; in fact they were, and still are, only marginally worse than today’s Nikons for pattern noise.

In reality the images are of course eminently usable – as the millions of 1Dx images used daily world-wide testifies; but they do need a teeny bit more effort when processing than files from a top-end Nikon camera, if the final images are to have the same degree of quality in terms of “clean-ness of file”.

There is also the question of a clipped Dynamic Range, but that’s an easy walk-around in most cases – neither Highlight Tone Priority or Safety Shift are the answer though IMO; the former just under-exposes the shot, and the latter drives me nuts, though it’s a damnably good idea in principle.

So this noise thing truly is my ONE AND ONLY gripe about this camera – up until this last week I had a few others based solely on my usage of other folks cameras, but those are now well and truly GONE.

On the “pros & cons” side of things, noise and clipped dynamic range are my only cons, and there are many pros that cancel them out – the real big one for my is the autofocus system which, at least when used with the new(ish) 200-400 and the latest firmware, is truly EPIC and seriously kicks Nikon into a cocked hat in terms of tractability, speed, accuracy and user control.

I’m working on a large pdf document all about autofocus with both Nikon D4/D4S and Canon 1Dx bodies that has wildlife photography and long lenses as the main bias, but it will give a lot of valuable information and knowledge to non-wildlife photographers and 5DMk3 owners as well. Again, email me for details – BUT IT WON’T BE FREE!

If I had the dough I’d buy a 1Dx and a 200-400 f4 tomorrow – perhaps I’d even dump Nikon all together for long lens action/wildlife photography.

But I haven’t, so unless a miracle happens and Canon suddenly feel like sponsoring someone who actually “knows about stuff” then there’ll be tears when this rig has to go back I can tell you…:(

Would I dump Nikon for all my photography where speed and autofocus are not required, like macro or landscape – not on your bloody life!

Many thanks to Reece Piper & Calumet UK, June Lown, and Chuck Westfall of Canon USA

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Camera Calibration

Posted on September 29, 2014 by Andrew Astbury

Custom Camera Calibration

The other day I had an email fall into my inbox from leading UK online retailer…whose name escapes me but is very short… that made my blood pressure spike. It was basically offering me 20% off the cost of something that will revolutionise my photography – ColorChecker Passport Camera Calibration Profiling software.

I got annoyed for two reasons:

Who the “f***” do they think they’re talking to sending ME this – I’ve forgotten more about this colour management malarkey than they’ll ever know….do some customer research you idle bastards and save yourselves a mauling!
Much more importantly – tens of thousands of you guys ‘n gals will get the same email and some will believe the crap and buy it – and you will get yourselves into the biggest world of hurt imaginable!

Don’t misunderstand me, a ColorChecker Passport makes for a very sound purchase indeed and I would not like life very much if I didn’t own one. What made me seethe is the way it’s being marketed, and to whom.

Profile all your cameras for accurate colour reproduction…..blah,blah,blah……..

If you do NOT fully understand the implications of custom camera calibration you’ll be in so much trouble when it comes to processing you’ll feel like giving up the art of photography.

The problems lie in a few areas:

First, a camera profile is a SENSOR/ASIC OUTPUT profile – think about that a minute.

Two things influence sensor/asic output – ISO and lens colour shift – yep. that’s right, no lens is colour-neutral, and all lenses produce colour shifts either by tint or spectral absorption. And higher ISO settings usually produce a cooler, bluer image.

Let’s take a look at ISO and its influence on custom camera calibration profiling – I’m using a far better bit of software for doing the job – “IN MY OPINION” – the Adobe DNG Profile Editor – free to all MAC download and Windows download – but you do need the ColorChecker Passport itself!

I prefer the Adobe product because I find the ColorChecker software produced camera calibration profiles there were, well, pretty vile in terms of increased contrast especially; not my cup of tea at all.

5 images shot at 1 stop increments of ISO on the same camera/lens combination.

Now this is NOT a demo of software – a video tutorial of camera profiling will be on my next photography training video coming sometime soon-ish, doubtless with a somewhat verbose narrative explaining why you should or should not do it!

Above, we have 5 images shot on a D4 with a 24-70 f2.8 at 70mm under a consistent overcast daylight at 1stop increments of ISO between 200 and 3200.

Below, we can see the resultant profile and distribution of known colour reference points on the colour wheel.

Here’s the 200 ISO custom camera calibration profile – the portion of interest to us is the colour wheel on the left and the points of known colour distribution (the black squares and circled dot).

Next, we see the result of the image shot at 3200 ISO:

Here’s the result of the custom camera profile based on the shot taken at 3200 ISO.

Now let’s super-impose one over t’other – if ISO doesn’t matter to a camera calibration profile then we should see NO DIFFERENCE………….

The 3200 ISO profile colour distribution overlaid onto the 200 ISO profile colour distribution – it’s different and they do not match up.

……..well would you bloody believe it! Embark on custom camera calibration profiling your camera and then apply that profile to an image shot with the same lens under the same lighting conditions but at a different ISO, and your colours will not be right.

So now my assertions about ISO have been vindicated, let’s take a look at skinning the cat another way, by keeping ISO the same but switching lenses.

Below is the result of a 500mm f4 at 1000 ISO:

Profile result of a 500mm f4 at 1000 ISO

And below we have the 24-70mm f2.8 @ 70mm and 1000 ISO:

Profile result of a 24-70mm f2.8 @ 70mm at 1000 ISO

Let’s overlay those two and see if there’s any difference:

Profile results of a 500mm f4 at 1000 ISO and the 24-70 f2.8 at 1000 ISO – as massively different as day and night.

Whoops….it’s all turned to crap!

Just take a moment to look at the info here. There is movement in the orange/red/red magentas, but even bigger movements in the yellows/greens and the blues and blue/magentas.

Because these comparisons are done simply in Photoshop layers with the top layer at 50% opacity you can even see there’s an overall difference in the Hue and Saturation slider values for the two profiles – the 500mm profile is 2 and -10 respectively and the 24-70mm is actually 1 and -9.

The basic upshot of this information is that the two lenses apply a different colour cast to your image AND that cast is not always uniformly applied to all areas of the colour spectrum.

And if you really want to “screw the pooch” then here’s the above comparison side by side with with the 500f4 1000iso against the 24-70mm f2.8 200iso view:

500mm f4/24-70mm f2.8 1000 ISO comparison versus 500mm f4 1000 ISO and 24-70mm f2.8 200 ISO.

A totally different spectral distribution of colour reference points again.

And I’m not even going to bother showing you that the same camera/lens/ISO combo will give different results under different lighting conditions – you should by now be able to envisage that little nugget yourselves.

So, Custom Camera Calibration – if you do it right then you’ll be profiling every body/lens combo you have, at every conceivable ISO value and lighting condition – it’s one of those things that if you don’t do it all then you’d be best off not doing at all in most cases.

I can think of a few instances where I would do it as a matter of course, such as scientific work, photo-microscopy, and artwork photography/copystand work etc, but these would be well outside the remit the more normal photographic practices.

As I said earlier, the Passport device itself is worth far more than it’s weight in gold – set up and light your shot and include the Passport device in a prominent place. Take a second shot without it and use shot 1 to custom white balance shot 2 – a dead easy process that makes the device invaluable for portrait and studio work etc.

But I hope by now you can begin to see the futility of trying to use a custom camera calibration profile on a “one size fits all” basis – it just won’t work correctly; and yet for the most part this is how it’s marketed – especially by third party retailers.

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Speed Light Photography

Posted on September 23, 2014 by Andrew Astbury

Speed Light Photography – part 1

First things first, apologies for the gap in blog entries – I’ve been a bit “in absentia” of late for one reason or another. I’ve got a few gear reviews to do between now and the end of the year, video tutorial ideas and requests are crawling out of the woodwork, and my ability to organise myself has become something of a crumbling edifice!

I blame the wife myself………………..

But I’ve come to the conclusion that for one reason or another I’ve become somewhat pigeon-holed as a wildlife/natural history photographer – going under the moniker of Wildlife in Pixels it’s hardly a big surprise is it..

But I cut my photographic teeth on studio product/pack shot and still life work – I loved it then and I still do. And there’s NOTHING that teaches you more about light than studio work – it pays dividends in all aspects of photography, wildlife and landscape work are no exception. Understanding how light behaves, when it’ll look good and when it’ll look like a bag of spanners is what helps capture mood and atmosphere in a shot.

The interaction between light and subject is what makes a great image, and I do wish photographers would understand this – sadly most don’t.

To this end I’ve begun to teach workshops that try to give those attending a flavor of the basic concepts of light by introducing them to the idea of using their speed lights to produce images they can do 365 days a year cum rain or shine – high speed flash, and simple product still life.

Both styles demand a high level of attention to detail in the way the light produced by the speed lights bends and wraps around the subject. Full-blown studio lights have the benefit of modelling lights so that you can see this before you take the shot, but using speed lights means you have to imagine what the light is doing, so it’s level of difficulty begins high, but decreases with practical experience.

A basic 3 light setup with speed lights can produce some really soft and moody lighting with ease.

A basic 4 light setup with speed lights can produce some really soft and moody lighting with ease.

This Black Label shot went a bit bonkers in the final stages with the addition of smoke, but it gives you an idea of the subtlety of lighting that can be achieved with speed lights.

As for the setup, here’s a shot before I introduced the glass….

Simple setup for the Black Label shot – note the well-appointed studio!

…featuring that most valuable of studio photographers tools, the Voice Activated Light Stand..!

Four SB800’s in all, the one on the right is running at 1/2 power and is fitted with an Interfit Strobies softbox and is double diffused using a Calumet 42″ frame (available here) and white diffuser – this constitutes the main light.

Just look at the size of the diffused disc on the face of that 42″ frame – all that from a poxy 2″x1″ flash head in less than 16″ – epic!

The SB800 on the left, fitted with another softbox is turned down to 1/64th power, and is there solely to illuminate the label where it wraps around the left edge of the bottle, and to get a second neck highlight. Although their is light emanating from it, its greatest effect is that of “bouncing” light from the right hand source back in to the bottle.

The V.A.L.S. is fitted with a third speed light that has a diffused snoot – note the expensive diffusion material and the highly engineered attachment method – kitchen towel and rubber band! The sole purpose of this tiny soft light is to just help pull out the left side of the bottle cap from the intensely dark background towards the top of the shot.

The 4th SB800 is fitted with a 30 degree honeycomb and a “tits ‘n ass”; or TNA2 to be more correct; filter just to give a subtle warm graduation to the background.

Speaking of the background, this is a roll of high grade tracing paper – one of the most versatile materials any studio has, both as a front lit or back lit background, or as a diffusion material – just brilliant stuff, second only to Translum plastic, and a shed-load cheaper.

At the other end of the speed light photography spectrum is the most enjoyable and fascinating pastime of high speed liquid motion photography – a posh way of saying “making a mess”!

It doesn’t have to be too messy – just don’t do it on your best Axminster!

By utilising the IGBT (Isolated Gate Bipolar Transistor) circuitry given to us in speed lights we can deploy the very fast tube burn times, or flash durations, obtained at lower output power settings to our advantage.

Simple shots of water, both dyed and clear can produce some stunning captures:

Streams of water captured back lit against a white background illuminated by two speed lights.

The background for this shot (above) is an A1 sized sheet of white foam board illuminated by a pair of SB910s. The internal reflector angle is set to 35mm and the two speed lights are placed on stands about three feet from the background, just out of shot left and right, and aimed pretty much at the center of the board to facilitate a fairly even spread of light.

The power output settings for both speed lights is set to 1/16th which gives us 1/10,000th of a second flash duration.

Switching to tracing paper as a back lit background immediately puts us at a disadvantage in that it’ll cut the amount of light we see at the camera. But a back lit background always looks just that little bit better as it makes your lighting more easy to shape and control.

Doubling the speed light count behind the trace background to 4 now gives us the power in terms of guide number equal to your average studio light – but with full IGBT advantages.

Working a little closer to the background than we were with the white board/reflected light method we can very easily generate a smooth white field of 255RGB which will make our liquid splash shots really punchy:

Working about 3 feet from a translucent background illuminated by 4 SB800’s gives us a much flatter white background, especially when deploying a 150mm or 180mm macro lens.

Shot with a 180mm macro lens at ISO 260 and f16 we have bags of depth of field on this shot.

Using 4x SB800s we can dial in the correct background exposure using the flash output power and camera ISO – we want a background that’s just on the verge of “blinkies”. If we over expose too much for the background the light will wrap around the liquid edges too much, washing out the contrast and flaring – that’s something that muppet on Adorama TV doesn’t tell you!

Take a few shots holding the glass by the rim gives us a clean foot to the glass, so we can now go and make a nice composite in Photoshop:

Composite of a couple of splash shots and a couple of “clean foot” images….

Happy sodding Valentines day for next year everyone……..yuck, but it’ll sell all day bloomin’ long!

A while ago I posted an entry on this blog about doing splash shots using a method I call “long flash short shutter” HERE.

All the shots on this entry have been taken using the “short flash long shutter” method.

This latter method is the more versatile one of the two because it has a more effective “motion freezing” power; the former method being speed-limited by the 1/8000th shutter speed – and it’s more costly on batteries!

BUT………there’s always one of those isn’t there…?

Short flash long shutter utilises the maximum X-synch speed or the camera. This is the fastest speed we can use where the sensor is FULLY open, and it’s most commonly 1/250th sec.

Sussed the massive potential pitfall yet?

That’s right – AMBIENT LIGHT.

If any ambient light reaches the sensor during our 1/250th sec exposure time then WE WILL GET MOTION BLUR that will visually amount to the same sort of effect as slow synch, sharp image with under exposed blur trails.

So we need to make sure that the ambient light is low enough to render a totally black frame.

The “long flash short shutter” method works well in conditions of high ambient provided that the action can be frozen in 1/8000th sec. If your camera only does 1/4000th sec then the method becomes somewhat less useful.

Freezing action depends on a number of things:

1. Is the subject falling under gravity or rising against it?
2. How far away is the subject?

A body falling under gravity is doing around 10mph after it’s fallen 2 feet from a dead start, and a car doing 100mph looks a lot slower when it’s 200 yards down the road than it does when it’s 20 yards away.

Similarly, if we have a cascade of liquid falling under gravity through the frame of our camera and (to avoid the jug or pouring vessel) the liquid has fallen 6 inches when it enters the top of the frame, and 30 inches when it vacates the bottom of the frame; we have to take a few things into consideration.

The liquid is faster at the bottom of the frame than at the top – think Angel Falls – the water pulls itself apart (that’s why the images can look so amazing).
If we shoot close with a short lens the speed differential across the frame will be the same BUT the overall speed will be a little more apparent than if we shoot with a longer lens from further away.

An SB910 has a 1/16th power output duration of 1/10000th sec and an SB800 1/10,900th at the same output setting (OEM-quoted values). With a 70mm lens close up this can make a subtle difference in image sharpness, but fit a 180mm and move further away from the subject to maintain composition, and the difference is non-existent.

If you are throwing liquid upwards against gravity, then it’s slowing down, and will eventually stop before falling back under the effects of gravity – quite often, 1/8000th is sufficient to freeze this sort of motion.

Both “long shutter short flash” and “short shutter long flash” are valid methods, each with their own pluses and minuses; but the method I always recommend people start with is the former “long shutter” method – it’s easier!

When a shot features a glass remember one thing – drinking glasses were invented by a race of photographer-hating beings! Glasses transmit, reflect and refract light through a full 360 degrees and you can really end up chasing your tail trying to find the source of an errant reflection if you don’t go about lighting it in the correct manner.

And if you put liquid in it then things can get a whole lot worse!

I’ll be doing some very specific workshops with Calumet in the near future that will be all about lighting glass and metal, gloss and matte surfaces, so keep your eye open if this sort of thing interests you – IT SHOULD ‘cos it’ll make you a better photographer….!

The simplest “proper” glass lighting method is what we call “bright field illumination” and guess what – that’s the method used in all the above liquid shots.

Glass Photography – Bright Field & Dark Field illumination.

In the image above, I’ve photographed the same glass using the two ancient and venerable methods of glass photography – one is easy, the other a total pain in the ass; guess which is which!

I’m not going to go into this in detail here, that’ll be in a later post; but BRIGHT FIELD defines the outline of the glass with DARK lines, and DARK FIELD defines the glass white lines of WHITE or highlight.

If you guessed DARK FIELD is the pain the bum then you were right – you will see bits of your “studio” reflected in the glass you didn’t even know existed unless you get this absolutely spot on and 100% correct.

The nice thing about studio-style photography is that you have thinking time, without pressure from working with people, animals or weather and a constantly moving sun. You can start to work up a shot and then leave it over night, when you come back the next day and click the shutter everything is as you left it – unless you’ve had burglars.

You do develop a habit of needing more “grips” gear – you’ve NEVER got the right bit! But then again it’s far cheaper than the bad habit of tripod accumulation like my friend Malc is afflicted with!

Later Folks!

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The ND Filter

Posted on July 16, 2014 by Andrew Astbury

Long Exposure & ND Filters

long exposure,slow shutter speed,ND filter,CMOS sensor,noise

A view of the stunning rock formations at Porth Y Post on the Welsh island of Anglesey. The image is a long exposure of very rough sea, giving the impression of smoke and fog. 30 seconds @f13 ISO 100. B&W 10stop ND – unfiltered exposure would have been 1/30th.

The reason for this particular post began last week when I was “cruising” a forum on a PoD site I’m a member of, and I came across a thread started by someone about heavy ND filters and very long exposures.

Then, a couple of days later a Facebook conversation cropped up where someone I know rather well seemed to be losing the plot over things totally by purchasing a 16 stop ND.

The poor bugger got a right mauling from “yours truly” for the simple reason that he doesn’t understand the SCIENCE behind the art of photography. This is what pisses me off about digital photography – it readily provides “instant gratification” to folk who know bugger all about what they are doing with their equipment. They then spend money on “pushing the envelope” only to find their ivory tower comes tumbling down around them because they THOUGHT they knew what they were doing………..stop ranting Andy before you have a coronary!

OK, I’ll stop “ranting”, but seriously folks, it doesn’t matter if you are on a 5DMkIII or a D800E, a D4 or a 1Dx – you have to realise that your camera works within a certain set of fixed parameters; and if you wander outside these boundaries for reasons of either stupidity or ignorance, then you’ll soon be up to your ass in Alligators!

Avid readers of this blog of mine (seemingly there are a few) will know that I’ve gone to great lengths in the past to explain how sensors are limited in different ways by things such as diffraction and that certain lens/sensor combinations are said to be “diffraction limited; well here’s something new to run up your flag pole – sensors can be thought of as being “photon limited” too!

I’ll explain what I mean in a minute…..

SENSOR TYPE

Most folk who own a camera of modern design by Nikon or Canon FAIL at the first hurdle by not understanding their sensor type.

Sensors generally fall into two basic types – CCD and CMOS.

Most of us use cameras fitted with CMOS sensors, because we demand accurate fast phase detection AF AND we demand high levels of ADC/BUFFER speed. In VERY simplistic terms, CCD sensors cannot operate at the levels of speed and efficiency demanded by the general camera-buying public.

So, it’s CMOS to the rescue. But CMOS sensors are generally noisier than CCDs.

When I say “noise” I’m NOT referring to the normal under exposure luminance noise that a some of you might be thinking of. I’m talking about the “background noise” of the sensor itself – see post HERE .

Now I’m going to over simplify things for you here – I need to because there are a lot of variables to take into account.

A Sensor is an ARRAY of PHOTOSITES or PHOTODIODES
A photodiode exists to do one thing – react to being struck by PHOTONS of light by producing electrons.
To produce electrons PROPORTIONAL to the number of photons that strike it.

Now in theory, a photodiode that sees ZERO photons during the exposure should release NO ELECTRONS.

At the end of the exposure the ADC comes along and counts the electrons for each photodiode – an ANALOGUE VALUE – and converts it to a DIGITAL VALUE and stores that digital value as a point of information in the RAW file.

A RAW converter such as Lightroom then reads all these individual points of information and using its own in-built algorithms it normalises and demosaics them into an RGB image that we can see on our monitor.

Sounds simple doesn’t it, and theoretically it is. But in practice there’s a lot of places in the process where things can go sideways rapidly……..!

We make a lot of assumptions about our pride and joy – our newly purchased DSLR – and most of these assumptions are just plain wrong. One that most folk get wrong is presuming ALL the photodiodes on their shiny new sensor BEHAVE IN THE SAME WAY and are 100% identical in response. WRONG – even though, in theory, it should be true.

Some sensors are built to a budget, some to a standard of quality and bugger the budget.

Think of the above statement as a scale running left to right with crap sensors like a 7D or D5000 on the left, and the staggering Phase IQ260 on the right. There isn’t, despite what sales bumph says, any 35mm format sensor that can come even close to residing on the right hand end of the scale, but perhaps a D800E might sit somewhere between 65 and 70%.

The thing I’m trying to get at here is that “quality control” and “budget” are opposites in the manufacturing process, and that linearity and uniformity of photodiode performance costs MONEY – and lots of it.

All our 35mm format sensors suffer from a lack of that expensive quality control in some form or other, but what manufacturers try to do is place the resulting poor performance “outside the envelope of normal expected operation” as a Nikon technician once told me.

In other words, during normal exposures and camera usage (is there such a thing?) the errors don’t show themselves – so you are oblivious to them. But move outside of that “envelope of normal expected operation” and as I said before, the Alligators are soon chomping on your butt cheeks.

REALITY

Long exposures in low light levels – those longer than 30 to 90 seconds – present us with one of those “outside the envelope” situations that can highlight some major discrepancies in individual photodiode performance and sensor uniformity.

Earlier, I said that a photodiode, in a perfect world, would always react proportionally to the number of photons striking it, and that if it had no photon strikes during the exposure then it would have ZERO output in terms of electrons produced.

Think of the “perfect” photodiode/photosite as being a child brought up by nuns, well mannered and perfectly behaved.

Then think of a child brought up in the Gallagher household a la “Shameless” – zero patience, no sense of right or wrong, rebellious and down right misbehaved. We can compare this kid with some of the photodiodes on our sensor.

These odd photodiodes usually show a random distribution across the sensor surface, but you only ever see evidence of their existence when you shoot in the dark, or when executing very long exposures from behind a heavy ND filter.

These “naughty” photodiodes behave badly in numerous ways:

They can release a larger number of electrons than is proportional to their photon count.
They can go to the extreme of releasing electrons when the have a ZERO photon count.
They can mimic the output of their nearest neighbors.
They can be clustered together and produce random spurious specks of colour.

And the list goes on!

It’s a Question of Time

These errant little buggers basically misbehave because the combination of low photon count and overly long exposure time allow them to, if you like, run out of patience and start misbehaving.

It is quite common for a single photodiode or cluster of them to behave in a perfect manner for any shutter speed up to between 30 seconds and 2 minutes. But if we expose that same photodiode or cluster for 3 minutes it can show abnormal behavior in its electron output. Expose it for 5 minutes and its output could be the same, or amplified, or even totally different.

IMPORTANT – do not confuse these with so-called “hot pixels” which show up in all exposures irrespective of shutter duration.

Putting an ND filter in front of your lens is the same as shooting under less light. Its effect is even-handed across all exposure values in the scenes brightness range, and therein lies the problem. Cutting 10 stops worth of photons from the highlights in the scene will still leave plenty to make the sensor work effectively in those areas of the image.

But cutting 10 stops worth of photons from the shadow areas – where there was perhaps 12 stops less to begin with – might well leave an insufficient number of photons in the very darkest areas to make those particular photodiodes function correctly.

Exposure is basically a function of Intensity and Time, back in my college days we used to say that Ex = I x T !

Our ND filter CUTS intensity across the board, so Time has to increase to avoid under exposure in general. But because we are working with far fewer photons as a whole, we have to curb the length of the Time component BECAUSE OF the level of intensity reduction – we become caught in a “Catch 22” situation, trying to avoid the “time triggered” malfunction of those errant diodes.

Below is an 4 minute exposure from behind a Lee Big Stopper on a 1Dx – click on both images to open at full resolution in a new window.

Canon 1Dx
4 minutes @ f13
ISO 200 Lee 10stop

The beastly Nikon D800E fairs a lot better under similar exposure parameters, but there are still a lot of repairs to be done:

A 4 minute exposure on a D800, f11 at 200ISO

Most people use heavy ND filters for the same reason I do – smoothing out water.

The texture of the water in the top shot clutters the image and adds nothing – so get rid of it! D4,ISO 50, 30secs f11 Lee Big Stopper

Then we change the camera orientation and get a commercial shot:

Cemlyn Bay on the northwest coast of Anglesey, North Wales, Approximately 2.5 km to the east is Wylfa nuclear power station. Same exposure as above.

In this next shot all I’m interested in is the jetty, neither water surface texture or horizon land add anything – the land is easy to dump in PShop but the water would be impossible:

I see the bottom image in my head when I look at the scene top left. Again, the 10 stop ND fixes the water, which adds precisely nothing to the image. D4 ISO 50, 60 secs, f14 B&W 10 stop

The mistake folk make is this, 30 seconds is usually enough time to get the effect on the water you want, and 90 to 120 seconds is truly the maximum you should ever really need. Any longer and you’ll get at best no more effect, and at worst the effect will not look as visually appealing – that’s my opinion anyway.

This time requirement dovetails nicely with the “operating inside the design envelope” physics of the average 35mm format sensor.

So, as I said before, we could go out on a bit of a limb and say that our sensors are all “photon limited”; all diodes on the sensor must be struck by x number of photons.

And we can regard them as being exposure length limited; all diodes on the sensor must be struck by x photons in y seconds in order to avoid the pitfalls mentioned.

So next time you have the idea of obtaining something really daft, such as the 16 stop ND filter my friend ordered, try engaging your brain. An unfiltered exposure that meters out at 1/30th sec will be 30 seconds behind a 10 stop ND filter, and a whopping 32 minutes behind a 16 stop ND filter. Now at that sort of exposure time the sensor noise in the image will be astonishing in both presence and variety!

As I posted on my Book of Face page the other day, just for kicks I shot this last Wednesday night:

Penmon Lighthouse in North Wales at twilight.
Sky is 90 secs, foreground is 4 minutes, D4, f16, ISO 50 B&W 10 stop ND filter

The image truly gives the wrong impression of reality – the wind was cold and gusting to 30mph, and the sea looked very lumpy and just plain ugly.

I spent at least 45 minutes just taking the bloody speckled colour read noise out of the 4 minute foreground exposure – I have to wonder if the image was truly worth the effort in processing.

When you take into account everything I’ve mentioned so far plus the following:

Long exposures are prone to ground vibration and the effects of wind on the tripod etc
Hanging around in places like the last shot above is plain dangerous, especially when it’s dark.

you must now see that keeping the exposures as short as possible is the sensible course of action, and that for doing this sort of work a 6 stop ND filter is a more sensible addition to your armoury than a 16 stop ND filter!

Just keep away from exposures above 2 minutes.

And before anyone asks, NO – you don’t shoot star trails in one frame over 4 hours unless you’re a complete numpty! And for anyone who thinks you can cancel noise by shooting a black frame think on this – the black frame has to be shot immediately after the image, and has to be the same exposure duration as the main image. That means a 4 hour single frame star trail plus black frame to go with it will take at least 8 hours – will your camera battery last that long? If it dies before the black frame is finished then you lose BOTH frames……………

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Exposure Compensation

Posted on July 13, 2014 by Andrew Astbury

Exposure Compensation

Exposure Compensation – that’s something else that cropped up once or twice for the chaps on my recent Norwegian Eagle workshop!

We had something like 420 or more dives from eagles during the trip, and very few if any were shot with flat metering, or 0Ev compensation.

What is Exposure Compensation, and why do we need to use it?

It all begins with this little button:

D3 Exposure Compensation button – Nikon, Canon and most others use the same symbol.

Pushing this button and rotating your main command dial will select a certain exposure compensation value.

Why do we need to use Exposure Compensation though?

Cameras, for all their complexity and “intelligent whotsits” are basically STUPID! They don’t know WHAT you are trying to photograph, or HOW you are trying to photograph it.

They make a lot of very basic assumptions about what you are trying to do – 99.99% of which are WRONG!

The camera does NOT know if you are trying to photograph:

A white cat in a coal shed
A black cat in a snow storm
A white cat in a snow storm
A black cat in a coal shed

All it sees is a frame full of various amounts of light and shade, and depending on your metering mode (which should always be Matrix/Evaluative – see post here) it gives you an “average mean exposure value”.

Take a general scene of fairly low contrast under flat overcast light:

A scene as WE see it.

The same scene as the camera METER sees it.

Lighter tones within the scene.

Some darker area tones within the scene.

The exposure is governed by the PREDOMINANT tone.

As discussed in the previous metering article mentioned earlier, only MATRIX/EVALUATIVE takes the entire frame area into account.

Okay, so that scene was fairly bland on the old tonal front, so let’s have a look at something a little more relevant:

Straight off the camera with no processing. 1/2000th @ f4 1600ISO +1.3Ev

As the camera metered the scene WITHOUT compensation.

Why would the image be so dark and under exposed?

Well here’s an approximation of the cameras average tone “thought process”:

The approximate average value of the scene.

But if we look at some averages WITHIN the overall image:

Random tonal averages within the image.

We can see that the tonal values for the subject are generally darker than the average scene value, therefore the camera records those values as “under exposed”.

This is further compounded by the cameras brain making the decision that the commonest tonal value MUST represent “mid grey” – which it DOESN’T; it’s lighter than that – and so under exposing the image even further!

Now I’m not going to get into the argument about “what is mid grey” and do Nikon et al calibrate to 12%, 18%, 20% or whatever – to be honest it’s “neither here nor there” from our standpoint.

What is CRITICAL though is that we understand the old adage:

“Light Subject Dark Background = Under, or negative exposure compensation. And that Dark Subject Light Background = Over, or positive exposure compensation”.

Okay, but what are we actually doing?

In any exposure mode other than Manual mode, we are allowing the camera to meter the scene AND make the decision over which shutter speed or aperture to use depending on whether we have the camera in Av or Tv mode – that’s Canon-speak for A or S on Nikon.

If we are in shutter priority/S/Tv mode then the camera sets the aperture to give us its metered exposure – that thing that’s usually WRONG! – at the shutter speed we’ve selected.

If, as in the case above, we ADD +1.3Ev – one and one third stops of POSITIVE exposure compensation, the camera uses the shutter speed we’ve selected but then opens up the aperture WIDER than it’s “brain” wants it to.

How wide? 1.3 stops wider, thus allowing 1.3 stops more light into the the sensor during the exposure time.

If we were in Av/A or aperture priority mode then it’s the shutter speed that would take up the slack and become 1.3 stops SLOWER than the cameras “brain” wanted it to be.

Here’s an example of negative exposure compensation:

1/3200th @ f4.5 1000ISO -1.3Ev exposure compensation.

In this particular shot we’re pointing towards the sun – a “dark subject, light background” positive exposure compensation scenario, or so you’d think.

But I want to “protect” those orange highlights in the water and the brightest tones in the eagle, so if I “peg those highlights” just over a stop below the top end of the cameras’ tonal response curve then there is no way on earth they are going to “blow” in the final RAW file.

Manual Exposure mode can still furnish us with exposure compensation based on metering if we engage AUTO-ISO. If we decide we want to shoot continuously with a high shutter speed and a set aperture at a fixed ISO then our exposures are going to be all over the place. But if we engage AUTO-ISO and let the camera choose the ISO speed via the meter reading, we can use the exposure compensation adjustments just the same as we do in Av or Tv modes.

This get’s us away from the problem of fixed ISO Tv mode running out of aperture in low light or when very high shutter speeds are needed; or conversely, stopping the aperture down too far when the sun comes out! – I’ll do a breakdown on this method of shooting later in the year – it’s not without it’s problems.

Next time you get the chance to stand by a large lake or other body of water, just take a moment to notice that the water is dark in some places and light in others. ambient light falling on a moving subject can easily be very uniform and so the subject basically has the same exposure value all the time. But it’s the changing brightness of the background as the subject moves across it that causes us to need exposure compensation.

People seem to think there’s some sort of “magic” at play when they come out with me and I’m throwing exposure compensation values at them. But there’s no magic here folks, just an ability to see beyond “the subject, framing etc” and to actually “see the light” and understand it.

After all, when we click our shutters we are imaging light – the subject is, for the most part, purely incidental!

And there’s only one way you can learn to see light and grasp its implications for camera exposure, and that’s to practice.

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Auto Focus Work Out

Posted on July 1, 2014 by Andrew Astbury

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.

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

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:

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:

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:

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

Single Area AF

Single Area, or single point AF.

9 Point Dynamic Area AF:

9 Point Dynamic Area AF

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:

21 Point Dynamic Area AF

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:

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:

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

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.

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

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……..

“GIMME SOME, YOU MEAN BARSTARD!”

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Andy Astburys' Photography Blog

A general photography blog

Category Archives: Camera & Lens Techniques

Image Retouching

Image Retouching in Photoshop CC 2014

Image Sharpness

Image Sharpness

Shameless Plug Number 1.

Understanding Canon & Nikon Autofocus

for

Bird in Flight Photography

View Autofocus Points in Lightroom

Autofocus Drill-down

Long Lens Autofocus Considerations.

Canon 1Dx Sensor Noise

Many thanks to Reece Piper & Calumet UK, June Lown, and Chuck Westfall of Canon USA

Please consider supporting this blog.

Camera Calibration

Custom Camera Calibration

Speed Light Photography

Speed Light Photography – part 1

The ND Filter

Long Exposure & ND Filters

SENSOR TYPE

REALITY

It’s a Question of Time

Exposure Compensation

Exposure Compensation

Auto Focus Work Out

Auto Focus Work Out

Auto Focus Choices

How Dynamic Area AF Works

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

The Back Button Auto Focus Option

Conclusion

Image Retouching in Photoshop CC 2014

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Image Sharpness

Shameless Plug Number 1.

Understanding Canon & Nikon Autofocus

for

Bird in Flight Photography

Share this post:

Share this post:

Long Lens Autofocus Considerations.

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Many thanks to Reece Piper & Calumet UK, June Lown, and Chuck Westfall of Canon USA

Please consider supporting this blog.

Share this post:

Custom Camera Calibration

Share this post:

Speed Light Photography – part 1

Share this post:

Long Exposure & ND Filters

SENSOR TYPE

REALITY

It’s a Question of Time

Share this post:

Exposure Compensation

Share this post:

Auto Focus Work Out

Auto Focus Choices

How Dynamic Area AF Works

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

The Back Button Auto Focus Option

Conclusion

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