Slow flash – a misnomer

Nikon calls it “slow flash” when you use a slow shutter speed while using flash. You engage this in semi-automatic and automatic camera modes (P and A) by pressing the flash button an turning the wheel until you see the word “slow” on the top LCD display in the flash area.

This is a misnomer. The flash is fast – in the order of 1/1000th second. It is the shutter that is allowed to be slow in this “mode” (really just a technique). That is why another, more correct, term for this technique is “dragging the shutter”.

And you want to do that why? As readers here now, you want that in order to allow enough ambient light in, to avoid those dark backgrounds.

But can you use a slow shutter speed when using flash? Surely a shot at, say, 1/30th second will be all blurry?

Not necessarily. While there may be a little ghosting, if your subject is mainly lit by the flash, it will be as though it was shot at 1/1000th second.

That is why “slow flash” is such an unfortunate misnomer: it is”fast flash in a slow shutter image”. Which is why the Willems 444 Rule for indoors flash (400 ISO, 1/40th sec, f/4) usually results in crisp images.  Have you tried it yet?


The Willems Rule for Indoors Flash

So.. for indoors flash in a ‘normal’ environment (i.e. a room with not too much, not too little light), here is my new, “restated-as-an-easier-mnemonic” rule of thumb:

The 400-40-4 rule (a.k.a. the “4-4-4-rule”).

As a simple starting point, do the following:

  • Flash aimed 45 degrees up, behind you
  • 400 ISO
  • 1/40th second
  • f/4

That will give you an ambient light exposure of around -2 stops. Which looks like this:

Of course if your background is now too dark, you can raise ISO, lower f-number, or slow down shutter. If on the other hand the background is too bright, lower the ISO, select a faster shutter speed, or increase the f-number.

Often, simple rules of thumb are the secret to success. And simplicity is key – “4-4-4” sounds simple enough to remember, no?


Auto ISO

When you are using “auto ISO”, meaning the camera sets ISO for you, be careful.

In this mode, the camera will raise ISO and lower it – but it will get it wrong in some situations.

Low light. The camera will raise ISO to give you a handholding-suitable shutter speed. But do you want that? Or do you want quality (low ISO gives you that quality) and use a tripod? Night shots, twlight shots, fireworks, lightning: these are the obvious examples. For night shots, use low ISO and a tripod. So: low light: if you can use a tripod, use low ISO.

Motion needs. When there is enough light, the camera will lower ISO to give you good quality and shutter OK for handholding. But when you need that extra shutter speed, for sports, say, or for anything else that needs motion frozen, you need higher ISO. You may need 1600 or even 3200 ISO for hockey, but no auto ISO will give you that. So if you have motion, then raise ISO to suit.

My rules of thumb for ISO:

  • Outdoors, or low light with tripod, or studio shoots: start at 200 ISO
  • Indoors, even when using flash: 400 ISO
  • Difficult light – sports, motion, museums, churches: start at 800 ISO

In all cases, vary as able or as needed (if there is more light, use lower ISO; if you still get motion blur, use higher ISO).

Note – Auto ISO and manual will, on many cameras, give you a “aperture PLUS shutter priority” mode. This can be a cool thing to play with.


Mountains. Move them.

You know the saying, attributed to Francis Bacon? “IF THE MOUNTAIN WILL NOT COME TO MOHAMMED, MOHAMMED WILL GO TO THE MOUNTAIN”.

Photographers know this too – but we sometimes forget it. So let me remind you. When you have a background you do not like, or a wall with the wrong colour, or a ceiling that is too high, you can try to deal with it the best way you can.

You know how, right? So you read my blog – you know this. 4 -40- 400!

  • 400 ISO
  • 1/40th sec
  • f/4

And the flash aimed behind you.

Nice, but.. if you have a better background or a better wall, why not use that?

Ask your subjects to move.

And then you get..

So.. please remember that as a photographer, you can shape your environment. Do it, and your pics will be better.



Studio setup

A few readers asked about the “background post” of the other day – how was it lit?

Here’s how:

Studio Light (Photo: Michael Willems)

Four lights:

  • A softbox strobe as main light.
  • An umbrella strobe (not pictured) as fill.
  • And two speedlights: one with a Honl Photo snoot as edge light, and one with Honl Photo gel as background light.
  • All manual
  • One strobe and both speedlights fired with Pocketwizards; the other strobe with its cell.

That’s a very standard setup for me, and yes, you can learn to do this too.