Wildlife Flash Photography
Lessons Learned

Disturbed Wildlife?
I first witnessed a photographer using fill flash for wildlife photography many years ago. My initial thought was that it must disturb the animals. Contrary to this, I noticed that on most occasions animals had no reaction to fill flash. Sometimes, though, they would move away, not stay as long, or would act in a more nervous manner. Once in a while they would be startled and instantly run or fly away. I became curious about this, wanting to use flash to improve my own images in some situations but not wanting to disturb my subjects. When wildlife photographers disturb their subjects it jeopardizes the subject’s welfare1, ruins further photography of the subject, and ruins the shot for any other photographers who may be present. In some cases it endangers the lives of both the photographer and subject. It simply isn’t good, and no photograph is worth it. 
A General Rule
Experience, observation, boneheaded mistakes, and reason have shown me that if a flash unit is used only to fill in shadows on a sunny day when direct sunlight is already falling on the subject, and is positioned at an acute angle2 from the sun relative to the subject, it has no effect on most subjects most of the time. The reason is simple. When a flash unit is used to fill in shadows (fill flash), the light falling on the subject from the flash is set to be less intense3 than the light already falling on the subject from the sun. Since the subject’s eyes are already adjusted to the sun’s intensity, the less intense flash is barely noticeable. Set up a simple experiment and try it out with yourself as the subject. You’ll see that when the flash is positioned and set as described above it is not dazzling or surprising, and you do not end up seeing spots. When the flash is positioned at more than 90 degrees relative to the sun, you will see that it becomes much more noticeable and obnoxious. This is because the flash, not the sun, becomes the major source of light on the subject.

Resting Mother, Northern FlickerCommon Sense
What I have said above obviously applies to situations that are relatively open to the sun and sky. Common sense tells us that all bets are off when direct sunlight is not falling on the subject, or you are shooting under a dark forest canopy, on a very dark and cloudy day, at dawn, dusk, or at night. In these situations a flash is very disturbing. It produces an abrupt and dazzling burst of bright white light that frightens and temporarily blinds the subject. Flash should never be used on wildlife under these circumstances.  
The behavior of most primates is very sensitive to the use of flash, even when it is used properly and judiciously. These intelligent animals are more likely than others to take some action when unusual events occur around them. Although they may not be dazzled or shocked by a properly used flash unit, the most timid ones will move quietly away after one photo is taken. Some will tolerate a few flash photographs before going elsewhere. Others, most notably orangutans, may become curious about the flash. Not many things are considered dangerous by orangutans, and the burst of light tends to draw their attention and curiosity. This is not a good thing. In more than one case an orangutan has been drawn to a photographer by light from a flash unit, and has taken the camera and flash up a tree to investigate it. In one case I know about, the orangutan took the photographer’s entire equipment bag. This is not only dangerous, it can be expensive! Based on my own experiences and observations of others, I no longer use flash to photograph primates in the wild. I occasionally make an exception for Macaques, which are typically very bold and nearly unflappable.
Primates are not the only animals whose behavior is exceptionally sensitive to flash photography. I have noticed that the behavior of some birds is adversely affected by the use of flash. In one example that comes to mind, I noticed that my flash made a nesting northern flicker quite skittish. Although she did not stop going to her nest to feed the young ones, her stays at the nest were shorter and her actions were more abrupt and nervous in their nature. Upon noticing this I stopped using the flash and her behavior returned to normal. While the mother bird was off collecting food I then moved to a position that put me between the sun and the bird's favorite perch. This position would eliminate most shadows when the sun got lower. Then, in a stroke of luck, clouds moved in and diffused the light. A few hours later I got a good image of the resting mother bird, who actually went to sleep while I photographed her - a sure sign that she was not stressed. Patience, not the flash, made the photo.

Orangutan, Sarawak, BorneoConclusions and Advice
In case you were wondering, the images on this page were taken without any flash. In fact, of all the images on this web site at the time of this writing, only four images (2 insects, 2 primates) employed flash. My flash unit is the piece of equipment I could most easily do without, but once in a while it can be used to great benefit. It may be more difficult to get nice illumination and highlights in an animal’s eyes without using flash, but it can definitely be done. My advice is to be extremely conservative when considering the use of fill flash on wildlife. Put your subject, not your photograph, first. Use flash only when it is truly necessary, and use the minimum amount of light necessary for the job. Setting the flash output a full stop under the ambient light exposure often produces very nice results. You will sometimes find that you get more chances for good images without flash because some animals will stay in the area longer. When you do use flash, be sensitive to changes in the animal’s behavior and stop if you observe a change. It’s simply the right thing to do. 
Happy shooting!  

1 Some animals require specific foods that are scarce and found only in certain places during certain seasons. Causing an animal to leave a food source or expend energy avoiding you jeopardizes its welfare and can also jeopardize the welfare of any young it may have. This is particularly true of nesting birds, whose young must be fed almost continuously. In addition, primates are susceptible to human illnesses. Inadvertently drawing them into contact with us and our equipment by using a flash is a direct risk to their health. 
2 Acute angles are angles less than 90 degrees. See diagram.
For natural fill flash, the flash is usually set to between 1/3 and 1 stop under the ambient light exposure. Some modern flash units automatically reduce their output when they “think” they are being used as a fill-in light source. The goal is to lighten and open up, but not eliminate, the shadows. Setting the flash output to be equal to or higher than the ambient light exposure creates unnatural looking photographs in most cases. Extending the range of your flash unit by focusing the light more narrowly is a must when shooting wildlife with long lenses. There's nothing better for this than the Better Beamer flash extender by Visual Echoes. It's cheap, weighs next to nothing, and folds flat. It is made for use with lenses of 300 mm and longer. You can buy it through the Rue Catalog, among other places. 
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