Fill flash photography is used as a secondary light source to complement natural light. When used correctly it is a great way to improve your wildlife photography and I find it particularly good for bird photography.
There are three occasions when I’m inclined to use fill flash:
To soften shadows when the natural light is harsh
When the light is extremely bright such as at mid-day, there can be too much contrast because the bright parts are very bright, and the shadows are very dark. The camera cannot expose for this so you end up with either the highlights exposed correctly but no detail in the shadows, or the shadows exposed correctly with blown out highlights.
Fill flash photography can be used to provide some light to soften the shadows, allowing detail to be seen in both the shadows and the highlights.
The ideal solution is to shoot when the light is less harsh, but sometimes it is desirable to get the best shot possible under the circumstances. This happened to me wile waiting an entire morning for a bird to appear. Eventually I gave up as mid-day was approaching. As I was getting ready to go it decided to make an appearance! I was then able to use fill flash to get a decent shot despite the light being harsh.
On overcast days when there are no shadows
On an overcast day colors can look dull and the scene can look flat because of the lack of shadows (the contrast is too low). Fill flash photography can be used to increase the contrast, brightening the colors and adding shadow to give the final image more depth.
This effect is further enhanced if the flash gun is positioned to the side of the lens using a flash bracket.
The flash can also add a catchlight, creating a sparkle in the subjects eyes. If you use multiple flashguns watch out for more than one catchlight because it looks very unnatural.
To lighten a back-lit subject
A back lit subject often ends up as a silhouette because of the high contrast. The camera cannot expose for both the bright background and dark foreground, so the subject often appears dark. Fill flash can be used to lighten the subject which decreases the contrast, allowing the camera to show more detail.
Dappled light such as woodland
Another occasion when I use fill flash photography is when there is dappled light such as in a rainforest or any type of woodland.
How To use Fill Flash Photography
To take a fill flash shot simply set your exposure in your normal way. I use aperture priority mode most of the time. Set the flash to produce 1 – 2 stops less light by dialling in flash compensation.
For a mid-toned subject I default to -1 1/3 stops. If the subject is bright or light colored then use -1 2/3 or -2. If the subject is dark then use -1 or -2/3.
Many flash guns have an automatic fill flash setting (daylight balancing). This basically dials in about -1 stop of flash compensation. If you use this mode rather than standard TTL you will need to dial in 1 stop less compensation. I just use standard TTL and dial in the appropriate compensation and ignore the fill flash setting.
Although fill flash using TTL is automatic, the only thing you have to make sure is that the subject is close enough to your camera for the flash to be effective. For this reason flash extenders are usually used in wildlife photography.
Flash Extender – How to extend the range of your flashgun cheaply.
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