At some point in our collective photographic careers, we’ll need to deal with the flash. There’s no avoiding it. As much as you want to claim to be a “natural light photographer” you know that there will come a time when you’ll need to wrap your head around flash photography and use that darned thing.
I get the impression when speaking with photographers attending the Flash Photography Fasttrack workshops I run that flash photography is, well, scary. But it isn’t. I’ll let you in on a little secret: I love the flash. I know some photographers tut-tut about using the flash, claiming that only available light produces the best images. Pfft! Flash can be beautiful. Flash can be awesome. Flash can be… well, flash!
The modern flash is a thing of beauty. It’s also very smart. Inside the little flash head and body is a great deal of built-in intelligence that lets you use the flash pretty intuitively on its TTL (through-the-lens) mode, essentially the “automatic” mode on the flash.
The trick to mastering flash photography quickly is to realise what the flash does:
FLASH ADDS LIGHT INTO A SCENE
Now, I know you knew that, but let’s tease this out a bit more.
Fast Flash Facts
Your flash is able to output light at different intensities to light up a scene. It can cast light in a wide, but shallow arc or it can direct a beam of light that can reach further, but not as widely. It’s a little like using a garden hose that lets you set the nozzle to spray or jet — you get more reach on a jet stream, but the water doesn’t cover a very wide area.
You can also dial the amount of light the flash emits up (more light) or down (less light).
All of this has to do with how you want the flash to light the scene.
When you use your flash on its auto TTL mode, the smarts in it kick in and it is able to detect the proximity of objects in the scene and emit what it reckons is the right amount of flash to light the foreground in the scene. How far, wide and bright this lit section is depends on how you’re using the flash.
See – when you trigger the flash with your camera’s shutter button, the flash gun emits a pre-flash: a burst of rapid illumination that lights up the area in front of the flash. Your camera’s through the lens (TTL) exposure meter then detects the light as it falls on the scene and feeds this data back to your flash. The flash’s internal smarts then make the required calculations, figures in the ISO and aperture you’ve set on the camera and work out the correct amount of light to throw out and expose the scene.
That’s why it’s called TTL (through the lens) auto flash — because it detects exposure through the lens.
When shooting with a flash, you’re essentially adding a second exposure into the scene. Think of it this way:
- When you normally expose for a scene, you (or your camera) set the aperture, shutter speed and ISO values. This exposes for ambient light.
- When you add flash into a scene, you’re throwing additional light into the scene – which will light parts of it. However, this light is instantaneous – often in the hundredths or thousandths of a second. In that split, split, split of a second, the light illuminates something and the camera captures the exposure.
What this means is an important flash fact: shutter speed has no influence on flash exposure. Remember, the flash only exists for a very short duration – say 1/1000 of a second. Regardless of whether you have your shutter open for 1/200, 1/100 or 1/50 of a second, the flash will only light the scene for a fraction of the time the shutter is open. And in that fraction of time, it illuminates parts of the scene.
So, if your flashed image is too bright or too dark, don’t bother adjusting shutter speed. Look elsewhere. Flash exposure — the exposure that is created by the flash light — is determined by aperture, ISO and your flash power output (remember that you can dial this up or down).
Controlling Flash Exposure
Have a look at the back of your flash. You’ll notice buttons with + and – symbols on them. These let you override the auto flash exposure by allowing you to dial the exposure up or down. in much the same way that the +/- value on your camera lets you control exposure compensation. If you want more flash light on your subject, press +; less light, press -. Each time you +/- 1 on flash exposure value, you’re effectively doubling/halving the amount of light emitted.
When your flash exposure value is set to 0, your flash will attempt to create a balanced exposure of your subject, usually balancing this exposure with ambient exposure so that your subject is evenly exposed with the background.
There will be times when you don’t want this. You might want to capture the ambient exposure of your subject and use the flash to just fill in the shadows — fill flash. In this case, dial your flash exposure compensation down to -1 or -2/3 so that the light emitted is enough to just fill in the shadows slightly but still retain the distinction between lit and shaded parts. For instance, you may be photographing someone lit by sidelight from a window. The fill flash can fill in the shadowed portions of the person’s face, bringing out enough detail but still retaining the three-dimensional look of the person sculpted by window light.
Alternatively, you might want the flash to overpower ambient exposure, to make your subject pop right out of the background – in which case, dial your flash exposure compensation to +1 or more. You might be photographing someone standing against a very bright background — shooting into the sun, for instance. Because the background is bright, your camera’s TTL exposure meter will want to expose for this, rendering your subject as a silhouette. By using the flash to overpower ambient exposure, you ensure that the flash emits enough light to bathe your subject, even as your camera exposes for the background light.
Have a go with your flash. Don’t be afraid of it — learn to love the way flash light can add a creative punch to your photography.