Fill-in Flash, by Mark Blezard
Updated: Jan 28, 2021
Need a little more light with less shadow in your images?
As a rule, I hate using flash in photography. It casts sharp shadows, burns out whites, and causes redeye. However, there are some occasions when it can enhance a shot.
The most common is when being used as fill-in flash, especially outdoors. The best example I can think of is early evening when the light is fading but you can still manage shots without flash. However, your subject is lacking detail because the sun has pretty much gone.
So, many modern cameras have an automatic fill-in mode. However, I'm old school (as my battered Metz Flash is amply demonstrating. I like to manage my exposures manually, just as I did pre-digital.
This is the process. Let's say you are good to go at 125 shutter and an aperture of f5.6. What you need to know is that the smaller the aperture the greater the flashgun will work (because it has to push the light back through a smaller gap in order to capture the image. Therefore, you simply need to set your flashgun at a bigger aperture than you are already taking the image at, in this case f5.6, to gently enhance the image. A setting of f4 or f2.8 will work perfectly (because the image is already at an acceptable exposure). Again, the bigger the aperture the less light will be released, f2 will be even softer.
Now your flash is under-lighting the subject and therefore filling-in with a nice, gentle top-up of light.
There is a good chance that your modern camera will do all this for you. However, it always pays to fully understand what's going on in the background.