Last week, I did a blog post on Fill Flash for Bird Photography. I wanted to take time and go into a little more depth on how to use fill flash and its benefits.
Learning how to effectively use fill-flash will dramatically enhance your bird images. In many cases, birds are in trees or in shaded areas out of direct sunlight. The indirect lighting often actually increases color saturation in feathers, but we need to fill in the shadow areas. The same is true if the subject is in direct or harsh sunlight. This is where fill flash can take your images to another level.
According to Wikipedia: Digital TTL works as follows: Before the actual exposure one or more small flashes, called "preflashes", are emitted. The light returning through the lens is measured and this value is used to calculate the amount of light necessary for the actual exposure. Multiple pre-flashes can be used to improve the flash output. Canon refers to this technique as "E-TTL" and has later improved the system with "E-TTL II". The first form of digital TTL by Nikon, called "D-TTL", was used in a few early models. Since then, the superior "i-TTL" system has been used.
In using TTL, you have the option to control how much light is added by dialing in under or over exposure for the flash. FYI, it is a very good idea to read the camera and flash manuals thoroughly before venturing on a field trip. In some systems the compensation is made on the flash while in others flash compensation is dialed into the camera itself. Trying to figure out how your flash works with a bird in front of you is sure to be a frustrating experience.
In bird photography the large eyes of nocturnal species are particularly susceptible to red eye or steel eye. A good way to avoid red eye or steel eye is to move the flash off to either side of the camera. This prevents the light from the flash entering the subject's eye and reflecting directly back through the camera lens.
I can only speak of my experience with my Nikon D90, SB-800 and a Better Beamer. I can say that adding a flash to my bag has increased the quality of my images. That little "pop" of light added to your subjects increases your saturation, contrast and clarity.