As soon as a new photographer gets her hands on a Canon 580EXII or a Nikon SB-700, they inevitably want to use it ALL THE TIME… including when shooting on the beach in the middle of the day. Most photographers get frustrated when using fill-flash for the first time, but you really only need to know a few key things that will be discussed in this post, and you'll be well on your way to using that flash to its full potential.
Fill-flash is when a photographer uses a flash (commonly an on-camera speedlight) to fill in the harsh shadows created by the sun's light. This produces a more even and pleasing light on people, and gives the photo an overall more professional look.
When using fill-flash in dim conditions, there really is no trick to it. You simply dial in a low-power flash to cast a little light on the scene; however, things start to get complicated in bright conditions, which is where fill-flash is arguably the most useful.
Before we tackle the problem at hand, you should first go back and read this article on flash sync speed, or else none of this will make sense. The trouble is, in bright conditions, a fast shutter speed is required to achieve a proper exposure. The fast shutter speed means that the flash will fire during part of the exposure, but not cover the entire exposure.
The answer is to use high speed sync, which creates a series of short bursts of light that illuminate the subject for the entire exposure. Now that we've covered that common problem, check out these top 10 tips for fill-flash in photography.
Fill Flash Tip #1: Tone it down! The goal of fill-flash is to subtly fill in the harsh shadows, not to create studio lighting. Just kiss the subject with a tiny bit of light and the photo will look much more natural. If the flash is powered too high, the subject will be blasted with flat light and it will destroy the directionality of the sun's natural light. This includes ETTL/iTTL flashes. In my experience, they usually add just slightly too much light for my personal taste.
Fill Flash Tip #2: Match the color temperature of the ambient light. The light from a flash is extremely cool when compared to most ambient light situations, so you might consider putting a light gel on your flash in some situations, or at least use a light enough amount of light that the color disparity is less noticeable.
Fill Flash Tip #3: Don't miss the catch-lights! Photographers really go overboard about getting proper catch-lights in the eyes. Usually, the fill-flash will automagically add a little catch-light in the subjects eyes. If this is a very important shot and you want to get it perfect, remember this fact and consider adjusting the camera position to get the catch-light in a pleasing spot on the eye.
Fill Flash Tip #4: Make the leap to rear-curtain sync. Rear-curtain sync, also called second-curtain sync, will produce much more natural-looking results that the default front-curtain sync. Make this change in your camera and you'll be well on your way to more natural-looking ambient light.
Fill Flash Tip #5: Try a flash bracket. I only use a flash bracket when I'll be using flash for a whole day or a whole afternoon, like when I'm shooting a wedding. Flash brackets are cumbersome, but they do produce slightly better lighting in your photos by allowing some slight directionality of the light.