How many times have you framed the perfect shot, hit the shutter button at exactly the right moment, and then watched the whole scene fall apart as your camera whirred, clicked and focused its way right past the moment? We call this “shutter lag,” but that’s actually a misnomer. What we think of as “shutter lag” is really a combination of different delays, all of which are related to how your camera processes and records information.
Shutter lag is frustrating, but for many modern cameras the solution is quite simple. When you prefocus your camera, you also speed up your camera’s reaction time, and then shutter lag is less of a problem. And prefocusing has other benefits, too—here’s what they are.
Combat shutter lag by prefocusing
Your camera has to think about a lot of different things when you press the shutter button, especially when you’re shooting in auto mode. Part of what it’s doing is focusing on the scene, but it’s also adjusting for things like white balance and exposure, and it may also have to spend some time “charging up” before it can make the actual exposure. Depending on the age of your camera, its manufacturer and class (budget models tend to have more shutter lag than more expensive models) there can be a delay of up to three seconds between the moment you press the shutter button and when the camera actually captures the exposure.
If this delay is a problem for you, one of the best ways to get around it is to pre-focus. To do this, press down halfway on the shutter release button. This lets the camera know what to focus on—remember that most cameras will default to focusing on whatever is in the center of the frame, so you may need to press down, focus, and then recompose. When you pre-focus, you take all that extra processing out of the equation—which means that the camera can get straight to making the picture. The less processing it has to do, the faster it will respond.
Keep the shutter held half way down until your subject is right where you want him to be. Your exposure and focus will remain locked as long as your finger is halfway down on that button. Essentially, you're telling your camera what to focus on and how to expose the shot, but you’re also asking it to hold off for a moment until you're ready. Then when the perfect moment arrives, you can press the shutter button down all the way and snap the photo.
When to preset your focus and exposure
When you preset your focus, you stay one step ahead of the game. This is true even for cameras that don’t suffer from noticeable shutter lag, because pre-focusing avoids the difficultly of trying to lock on to a fast moving subject. So this is definitely a technique you want to be using whenever there's going to be action.
Let’s say you're at a playground and there are kids running around between the swings, slides, and merry-go-rounds—there’s no doubt that pre-focusing is going to help you get those photos. You can’t expect the kids to stop just because you want a photo of them, and you don’t want them to, either, because this is a prime opportunity to capture some great candid moments. Try pre-focusing on the merry-go-round (or slide, or swing set). Kids never stay on one piece of playground equipment for long, so it’s only a matter of time before one of them will jump on board. Keep your shutter button halfway down so you’ll be ready once the action moves your way.
Keep in mind that it takes practice to anticipate where your subject will go, and even more practice to decide where you should place your focus point. Kids can move pretty erratically, so that perfect focus point could change rapidly from one moment to the next. If you’re finding yourself with consistently blurry photos, keep practicing, but give yourself a break, too. Go for some shots of kids who are more or less stationary—playing in the sandbox, climbing on the monkey bars, playing hide-and-seek—these are all activities that include quiet moments, or moments where there isn’t a lot of fast movement.
If you're photographing a mountain, of course, it's not probably not going to jump away during shutter lag (if it does, I hope you stop worrying about photos and start worrying about making your escape). So presetting focus isn’t really necessary for stationary subjects, though I think it’s always a good idea to get into the habit.
Fast action sport is another example of a situation where you might want to pre-focus. Kids aren't the only ones who can't sit still—lots adults have traded that merry-go-round for a fast car or a snowboard. But if you’ve ever tried to capture racecars or snowboarders, you probably know that it’s a bit more difficult than capturing fast-moving kids. Maybe your racecar photos are all tail-light, no car. Shutter lag really becomes a problem when you’re shooting very fast moving objects, so it becomes doubly important to pre-focus. Just put your camera in burst mode and then press halfway down on the shutter button to lock on to a specific part of the track. Now switch to manual focus—that will keep your focus point right where it is even when your camera senses objects coming in and out of the frame. When the cars approach that spot, put your finger on the shutter button and don’t let go until the action has passed. You won’t need to keep your finger on the button while you wait, either—when you’re in manual focus mode the focus won’t change regardless of what you do with the shutter button.
Do this correctly and you’ll get a nice clean sequence of action shots. They won’t all be winners, but some of them are almost certain to be. Pick your favorite and delete the rest, or get creative and put together your own action sequence photo. And when you’re done, don’t forget to set your lens back to autofocus—if you forget you may end up missing an important shot the next time you pick up your camera.
If you look back through some of your photos and notice that a lot of them look like lost moments—people half in and out of the frame, the backs of heads etc.—you may find that the simple pre-focus method instantly improves the quality of your shots. You may still lose a moment or two but you won’t come away from every experience wishing you’d captured that one cool thing that happened, that thing that your camera couldn’t keep up with. When you pre-focus, that becomes a thing of the past.
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