Autofocus is so good on modern cameras that most photographers use it all the time. It seemingly never lets you down. But, let’s say it’s nighttime and you are going to do some shooting. You find a good spot. You set up your tripod. You go to focus your camera using the autofocus. You can feel the camera’s focus ring twisting back and forth, trying to focus. But it never gets there. The camera keeps hunting for a focus spot but never finds one.
Uh-oh. What are you going to do now?
Actually, this problem doesn’t arise only at night. Your camera will typically have trouble focusing in any really dark scene. So here are some tips for dealing with that situation and focusing your camera when it is dark:
1. Aim for the bright spot
Sometimes you can still use your autofocus. Even though it is dark, most night scenes will have a bright spot or two. They might be streetlights, or a lit-up building, or even the moon. That bright spot can be used to set your autofocus.
To do so, find a bright spot that is reasonably close to your desired plane of focus (i.e., the same distance away as your focal point). Autofocusing on that point should take care of your problem. Just focus on that bright spot in a normal fashion and your camera is now focused on something the same distance away as your subject. You should then be able to take your picture with proper focus.
2. Focus on the edge
Most cameras focus using something called contrast detection. That means the camera will have the best chance at finding something to focus on if you aim at the area of high contrast between something bright and the dark background. So don’t aim your focus point at the middle of the bright spot in your frame. Rather, focus on the edge of the bright point. The camera will use the contrast between the very light and the very dark tones to focus.
3. Use a flashlight
If you are attempting to autofocus on a relatively close subject, you can use a flashlight to assist with the focus. This is one of the many reasons to keep a flashlight in your camera bag.
To do that, shine your flashlight on your subject. That will lighten it up enough for the camera to focus on it. Set your focus, then you can turn off the flashlight and take your shot.
4. Recompose after focusing
Assume you now have your focus set using the methods set forth above. But to get that focus, you had to move your camera away from your desired composition to focus on the edge of a bright spot. Move your camera back to your desired composition to get the shot. Don’t refocus as you do so though – just move the camera and take the shot with the focus you’ve already set. (You will need to either hold the shutter button part way down, use focus lock, or focus and then turn off the AF so it doesn’t attempt to refocus once you have recomposed – or see #5 below.)