Speed Light Photography

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!

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.

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.

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....

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.

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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Flash Output Power

Flash output power raises a lot of questions when you are trying to decide how to spend your money.

A lot of people writing on the internet decry the versatility of portable speedlights and their use as studio-type lighting – something which is entirely wrong in my opinion; as there is nothing that can’t be done with them, as long as you have enough of them!

And you don’t have to take my word for it – just go and watch the worlds best exponent of the art, in my opinion anyway – Joe McNally. – then tell me if I’m wrong!

But with a top-of-the-line Nikon SB910 running at £340 and Canons new 600EXRT a cool £400 plus here in the UK, purchasing 10 to 15 of these puppies is a wallet-emptying proposition; though given the cash or sponsorship it’s the way I’d go all day long.

A lot of folk come to me with the same quandary – studio flash heads are a lot more cost-effective; notwithstanding their big limiting factor – lack of portability.

Leaving aside the other problems of many studio-style flash heads, namely lack of TTL and HSS/FP facility (though this can be walked-around on certain models with Pocket Wizards and the dark art of Hypersynch) they do give one big advantage – more photons for your buck.

But just how does one compare the flash output power of one unit/type with another – after all, this is what we want to know:

  • Can I get more light from flash A than I can from flash B
  • How many speedlights do I NOT have to buy if I get studio-style flash head C which costs 1.5x the price of one of my speedlights.

The problem is that manufacturers don’t make it easy to do direct comparisons of flash output power between brands and formats, and they tend to try and confuse the buyer with meaningless numbers and endless amounts of jargon.

Back in the days of manual-everything, we used to use flash in a very simple way using the units Guide Number.

The guide number is usually quoted as being at 100 ISO and at two values, one for metres and one for feet, and we use it with the following equation:

GUIDE No: = Distance x Aperture

So we might see a flash unit has a  guide number quoted as 40/131 at 100 ISO.  This means for example, that at 100 ISO and a flash to subject distance of 2.5 metres or 8.2 feet the correct aperture to use would be:

Guide No: divided by distance – in this case 40/2.5m or 131/8.2ft.

Either way the answer is 16, so we would set the shutter speed to the flash synch speed and the aperture to F16.

Simple!

Where things used to go a bit pear-shaped was when we introduced any form of output modifier such as a bounce board or diffuser because these spread and smooth the light and so reduce the number of photons falling on the subject by one or two stops.

But TTL flash metering soon put paid to all that grief.

Camera OEM Speedlights

Let’s compare a Nikon SB800 & SB910 – these have 100 ISO guide numbers of 38/125 & 34/112 respectively (published) – that’s right folks, the new one is weaker than the old one.

But by how much?

Well the old SB800 has a guide number that is 11.7% higher than the newer SB910, but what does this mean in terms of exposure value?

At a flash-to-subject distance of 3.4 metres, doing the maths says that our correct aperture would be 38/3.4 and 34/3.4 respectively. So the SB800 would put us at f11 (11.18 to be precise) while the SB910 would give us f10 – that’s an increase of over 1/3rd of a stop using the older unit.

When working with long lenses and wide apertures this extra 1/3rd of a stop gives me just that little bit more depth of field – and folk wonder why I don’t change mine!

Complications & Caveats

Nikon quote the two units above with guide numbers based on the head “zoom feature” being set to 35mm, which gives a fairly wide angle of lighting.  Someone said to me the other day that the new Canon 600EX was twice the power of the Nikon units I’ve already mentioned, simply because Canon quote the guide number for that device as a massive whopping 60!

The world is full of fools………..

Canon, in their infinite wisdom, quote that 60 value at a zoom head setting of 200mm.  The reality is that the guide number of this Canon unit varies between 26 with the zoom head at 20mm and 60 at 200mm – so in other words, give or take a bit, it’s pretty much in the same ball park as the Nikon units previously mentioned.

Canon speedlight naming policy tells you the units MAXIMUM guide number:

  • 600EX = 60 (metres)
  • 580EX = 58 (metres)
  • 550EX = 55 (metres)

The 550 specs also give you zoom length variations:

  • 105mm = 55 (metres)
  • 50mm = 42 (metres)
  • 17mm = 15 (metres)

Canon 600EX vs Nikon SB800 zoom lengths:

  • 105mm = 58 vs 56 (metres)
  • 50mm  = 42 vs 44 (metres)
  • 14mm = 15 vs 17 (metres)

Light leaves a flash unit in a cone of sorts, and the zoom heads on speedlight style units gather this cone of light so it basically matches the angle of view of the lens you are using and results in an efficient distribution of light across the image area – that’s the theory anyway.

Making the cone “tighter” forces the photons released by the flash into a more concentrated area, thus increasing the number falling on the subject and so increasing the overall exposure value.

So when we use guide numbers to compare various flash units we must ensure that we are comparing the units on a level playing field – in other words, the values we use are for the same “cone or reflector angle”.  And if the manufacturers use different reflector angles when assessing their flash guide numbers for promotion to the public, then you guys ‘n gals run the risk of being hood-winked into buying something that ain’t strictly what you thought it was when you ordered it.

So how do speed light style flash units stack up against studio type units?

Notwithstanding the lack of FP/HSS and any TTL metering problems, studio-type flash heads have guide numbers that are usually quoted as being “with standard reflector”.  This standard reflector is something which gathers those photons and shovels them out in a 50-55 degree spread; think “standard lens” on the image diagonal.

Current top end Nikon speed lights (and Canon) have guide numbers of sub 40 at 35mm reflector angles, and those equate to roughly 64 degrees diagonal coverage.  So if we were to “tighten them up” to 50 or 55 degrees we could, as a rough guide, round the guide numbers up to 42m or 44m.

Now we are on a more even playing field.

A Bowens Gemini 500R is quoted by Bowens as having a guide number of 85 with a standard reflector, so let’s be a bit cavalier with the numbers and say that it’s double the guide number of SB800/910 or 580EX etc.

So roughly how many speed lights is this puppy going to be equivalent to in terms of real flash output power ?

Hands up those who think two………….wrong!

This is where everything you thought you knew about exposure turns to shit in front of your very eyes (but not really!), and it’s called the Inverse Square Law.

Inverse Square Law

Now listen folks, this is as simple or as complicated as you care to make it!

When we capture a scene we capture a 2 dimensional plane filled with photons travelling towards us.

When we shine any light on an object we are actually throwing a flat sheet of light at it. This sheet is expanding outwards as it travels towards the subject because the photons in that sheet of light are all diverging.

So, let’s look at something tangible as an analogy – metric paper sizes!

How many sheets of A3 paper fit on a sheet of A2 paper?

That’s right, TWO – we’ve effectively doubled the surface area of the paper.

Now exposure works in stops – and making a 1 stop change in exposure effectively doubles or halves the exposure value depending on which way we’ve made the adjustment.

So moving from A3 to A2 is like making a 1 stop change in exposure; we’ve doubled the surface area of the paper.  BUT – we’ve not doubled the papers physical dimensions.

What paper size is twice the width AND twice the height of A3 – yep, that’s right, A1.

And how many sheets of A3 fit on a sheet of A1 – right again, 4.

So we have quadrupled the papers surface area – in exposure terms that would equate to 2 stops.

Now imagine a projector throwing an image onto a big screen and the screen to projector distance is 4 metres.  We go to the screen and measure the size of the projected image and it’s 1.5 metres by 2 metres.

How big will the image be if we move the projector to 8 metres from the screen?

Answer – 3 metres x 4 metres. (and the brightness of the image will have gone down by 2 stops).

And if we move the projector to 2 metres from the screen the image will be 0.75 metres x 1 metre. (and the brightness of the image will have increased by 2 stops!).

Inverse Square Law, Lights & Distances

Let’s say we have a theoretical flash with a metres guide number of 80.

If the subject is 10 metres from the light we need an aperture of f8 because 80/10 = 8.

If we now move the light to 5 metres from the subject our aperture decrease to 80/5 = f16

Halving the light-to-subject distance means we increase the overall intensity of the light (its effective flash output power) by 2 stops, so we have to reduce our overall exposure by two stops to compensate; otherwise we’ll just end up with 2 stops of over exposure.

And of course if we move the light away to 20 metres from the subject the inverse applies and we effectively reduce the flash output power by two stops and we’ll have to open the aperture up by two stops to avoid under exposure.

But what do we have to do in order to use f16 at 10 metres AND get correct exposure?

Use a flash with a guide number of 160 is what we’d need to do – it really is that simple.

Reality

So, how many guide number 45 speed lights would we need to equal one guide number 90 studio flash head in terms of effective flash output power?

Well it isn’t two – oh that we should be so lucky!

If we have two speed lights mounted together their cumulative guide number is equal to the square root of the sum of the squares of their individual guide numbers!

Sounds scary, but the answer is 63 or thereabouts.

But here’s the thing about photo-maths – it usually ends up as something really simple and this is no exception.

If you want to double the guide number you always need 4 identical units.

Do not forget what I’ve said above about published guide numbers – you have to ensure that the values were obtained using equal criteria, and manufacturers sometimes don’t always like to furnish you with the information you need in order to do easy comparisons.

Have they got something to hide – you may think that, but I couldn’t possibly comment!

What really does piss me off the meaningless crap they do furnish you with – watt-second, w/s, watt/sec or if you like Joules values.

The only thing these values do is inform you of the “potential energy” available at the capacitor; it’s no measure of how efficiently the flash tube converts that power into photons – and the photons is ALL we’re really interested in.

Other things such as tube temperature can have dramatic effects on both light output and the colour of that light.

Conclusion

This post has been a bit of a ramble but I’ve tried as best I can to give you a rough guide on how to compare one flash source with another.

Different photographers require different things – if all you want to do is shoot portraits and still life then shutter speeds above 1/250th synch are of little importance in general terms, so access to HSS/AutoFP via speed lights isn’t needed, and normal studio lights would be a far more economical proposition.

But on the other hand 8 speed lights in one bank, and two more banks of 4 speed lights each – all HSS/AutoFP compliant – crikey, the photographic possibilities are endless, and readily achievable – if your bank balance is endless too!

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