In his latest video, wildlife photographer and educator Steve Perry talks about specific autofocus problems to be aware of in the field that could prevent you from getting sharp images.
He calls these “false positives,” and by that he means times when the camera will erroneously indicate focus has been acquired. While this is more likely to occur in low-light shooting situations, it can also happen when the animal subject is low contrast or when using slower lenses or lenses with teleconverters attached. I’ve also noticed it can happen when shooting through tall grasses or thick foliage which will lower the contrast in a scene as well. Perry shares a few more hints on how you can tell the camera system is probably going to be fooled.
Now that you know what to look out for, how can it be fixed? It’s actually quite a simple technique, but the hard part to deal with is the time it takes to perform while hopefully your subject isn’t scurrying off. Check out the video above and get ready to improve your wildlife autofocus technique next time you’re in a tricky situation.
This video was about 8 minutes too long.
Summary:
Focus on your subject's eye, preferably with the centre focusing point, take some shots, manually unfocus the lens, reauto-focus, take some more shots. Repeat this process as much as you can. This process is especially useful in low-light or low-contrast scenarios.
Sometimes focusing on the eye can focus on slightly the wrong spot (the eye brow, eye-lid, etc), doing this allows the camera to choose slightly different things to get a lock on which increases your chances that the focus will be tack-sharp on the eye.
People are free to make their videos as long as they like, but there is no reason this video couldn't have been 1:00 - 1:30 minutes because it is an otherwise good tip.