Flash Photography - Don't Panic!

Flash photography takes you from using existing (ambient) light, and gives you the ability to add your own in creative ways.

However, there's one key aspect that you need to know before you start.

Adding a flash means that for every photograph, there's TWO simultaneous exposures to consider.

1. The ambient light which you control as usual with your ISO, shutter speed and aperture. Exactly as you would if your camera had no flash.
2. The flash-provided light which is controlled by several things:
   1. The flash power (light intensity)
   2. The position of the flash (light direction... this lights the bits of your subject that you want... and it's important for creating pleasing shadows too for that 3D effect/realism).
   3. The distance between the flash and the subject (closer = brighter, more distant = darker)
   4. Light modifiers (coloured gels, scrims, snoots, umbrellas/softboxes, reflectors, or surfaces to bounce off)... all sacrifice a bit of light (to varying degrees) to concentrate or diffuse the light, change the colour, or add creative effects/patterns.
   5. Camera ISO/Aperture (but NOT shutter speed unless high speed sync is used). The aperture impacts the amount of flash light entering the camera, just as much as ambient light. ISO also amplifies the recorded readings from the sensor, of both ambient and flash light. The shutter doesn't impact it due to the insanely short duration of the flash pulse. If the flash of light is shorter than the shutter speed, then all the flash light is recorded.

How do I handle two exposures?

There are many ways to do it but the big three are:

• Flash dominant:
  • Use the flash to provide most of the light in dark situations, but let a little ambient in (usually with a slow shutter speed in a process called "dragging the shutter"). Basically, use the flash to literally put a spotlight on the subject or their most interesting bits (which gives the flash a "key light" role), and dim the rest. If you take this to extreme, you expose for the intense, flash-lit areas as "normally exposed" and render the rest of the image black, this effect creates "Low key" shots.
  • Use the flash in normal brightness to intentionally over-expose the background (flash pointed at background which makes the flash a "back light"), and expose for the subject that's exposed to a normal brightness level. This renders the background white, and the subject a brighter colour. This extreme version creates "High key" shots.
• Ambient dominant:
  • Let a large amount of ambient light do most of the work, and use flash to brighten shadowed areas. This is called "Fill flash" or "Fill light"which reduces contrast/dynamic range and is generally more flattering for portraits. Fashion photographers do this in bright daylight conditions all the time.
  • Let the ambient do most of the work, but this time, sculpt the shadows/reflections with small amounts of flash lights where it is most visually pleasing. "Hair lights" are a common example in portraiture, but they're often called "rim lights" on object edges. Basically, lighting edges. The terminology gets a bit murky when it comes to important details being lit... it could be a key light if it's really important, or a fill light in other situations. Some photographers even have primary secondary, and tertiary "key lights" while rendering all the "fill lights" as equal. It really depends on the complexity of the setup.
• A balanced approach:
  • Balance the ambient exposure with the flash exposure... This usually means you intentionally underexpose (darken) the ambient exposure by 1-2 stops, for contrast, then selectively light the bits of the scene (subject, key details behind them) this is often called a "spot light", and if only the edges of the subject are lit, a "rim light". Naturally you'd put a "key light" or two on the subject as well.

I know I said two exposures.... but.....

For each light (flash) you add, you need to treat it as it's own exposure, as it is ultimately set up. So you just need to set one up at a time... tweak until your happy, then disable it an work on the next one.

Aaah! I'm starting to panic here!

While it's true that in complex studio setups, you can have anything from one to a dozen lights. One light is common, two is rarer but still popular, three's getting "up there", but three probably covers 99% of situations.

Don't worry, it sounds technical, but there are systems such as "Through the Lens" (TTL) flash systems which automate a lot of the process... but it only reduces your role a little bit.

You still need to choose where to put your flash, and of course, make sure the light it gives is flattering or as intended....