Shutter speed is critical for depicting or eliminating motion. A very fast shutter (1/500 or faster) may be needed to freeze motion completely. However, preserving some element of motion in an image can add to its impact. Photographs of birds in flight with their wingtip feathers blurred, for example, can be more dramatic than complete stop-motion images. To do this, play with different shutter speeds to find the right one for a given species.
Generally, flash isn't useful or practical in wildlife photography, because the distance is too great---and you want to avoid disturbing the animals, thus ruining your chance at more great shots. As a result, you may need to use a higher ISO setting than usual when light levels are low. Watch out, though---very high ISO settings can yield noisy images. You'll need to play around a bit to find a combination of aperture, ISO and shutter speed that will give you crisp images with adequate exposure but not too much noise. In good lighting, use the lowest ISO available to minimize image noise.
Most of the time, you won't be able to get very close to wildlife and will need a zoom or telephoto lens to bring the subject closer. If you're using a long lens or high zoom factor, your best bet is to stabilize your camera on a tripod (don't forget to turn vibration reduction off, and use a cable shutter release, to get the sharpest images). If a tripod isn't feasible and you're hand-holding the camera, make sure your shutter speed is high enough to compensate for camera shake---motion you aren't aware of and can't control that can ruin your images. A good general rule is to use a shutter speed at least as high as the focal length you're using. For example, if your lens is 200 millimeters, you will probably get clear hand-held images with a shutter speed of 1/200s or faster.
Depth of field
Depth of field can radically alter the feeling of an image. A crisply focused subject with a blurred background gives a portrait-like feel, versus the more documentary look of an image with both background and foreground in sharp focus. For shallow depth of field (only the subject in clear focus), use the largest aperture (lowest F stop number) available. Higher F stops (smaller apertures) will give you images with greater depth of field. For wide angle landscape or scenic shots, you should aim for an F stop of 20 or higher.
Article Written By Peggy Hansen
Peggy Hansen holds a Bachelor of Science in biology from UC San Diego, Doctor of Medicine from UCLA, and completed postgraduate training at Stanford, Duke and Harvard. An award-winning writer and photographer, her work has been featured in Catnip, Herbalgram, Porter Gulch Review, and many online pieces. She's also a commentator for KQED-FM