Has this happened to you? You pack up your camera and go to a football game. It's a great game, and you're sure you're capturing some fabulous images. You've got a perfect, clear view of the field, a good telephoto lens and shots of all the best moments. When you arrive home, you can't wait to see what you've got. You load the memory card up on your computer and you open up your photos in Photoshop and...
They're all blurry. Every single one of them. What happened?
Well, you've been visited by the photographer's scourge--blurry images. They happen to all of us, even experienced photographers. The reason is simple probability. You're not always going to be able to lock focus where you want it. Sometimes your subject is just moving too fast and erratically. Sometimes your autofocus system doesn't know what the subject is. And sometimes it's just because you made an error.
The truth is that you can't always avoid taking blurry photographs. But once you understand what causes them, you can dramatically reduce their numbers.
Last week I got a message from Dawn Sprowls, a reader who asked this very question: Why are these photographs blurry? Let's take a look at the examples she sent.
The first clue about this particular image is that it isn't blurry from foreground to background. In fact, the background is actually quite sharp. What does this mean? Put simply, it means that Dawn's autofocus system locked on the background instead of on the subject, which produced a photo with crystal-clarity in all the wrong places. This is a common problem with autofocus, especially in this type of situation--where there is a lot of movement in the scene and your autofocus system may have some difficulty figuring out what your subject is.
How to fix it
Pre-focusing is one way to make sure that your camera knows where your subject is going to be, so that it will already have the correct focus when you make the exposure. In this case, Dawn could have focused on the ground (by pushing the shutter button half-way and then keeping it there) and then waited until the action arrived in that spot. Then, when she finally pushed the shutter button down all the way, she would have an image with perfect focus in exactly the right place. Unfortunately football isn't always that predictable, so another option is to use the focus/recompose method. To do this, place your subject in the center of the frame and press that shutter button down halfway, then move your camera so that your subject is in the position where you want him to appear in the shot. This works best when the action slows down, because you'll need some time to lock focus, then recompose and shoot.
If you're familiar with your camera's focus-points system, this is the perfect situation to use it because you'll avoid that focus/recompose step. Place your focus point in the part of the frame where you want to record the action, then place your subject under that focus point, focus, and make the exposure. Switching on continuous focus will also help (that's the setting that allows your autofocus system to make fine adjustments to the focus as your subject moves).
Here's the second example Dawn sent:
Dawn shot this image at 1/200th of a second, which doesn't seem like a slow shutter speed--however for a football game, this is way too slow to capture all but the more idle moments. Football players move fast, so a fast shutter speed is required to freeze the action--otherwise you'll get motion blur, which is what happened in this image.
How to fix it
Sporting events really require a speed of 1/500th or more--however Dawn was a bit stuck in this situation because she was already shooting at a high ISO with a reasonably large aperture. Because this was a low light situation, a faster lens would have helped her get the shutter speed required to freeze the action.
It might be your first instinct to switch on a flash for this situation, but remember that you're probably not going to be close enough for the flash to have any effect on your image. And even if you are, flash photography at an event is a morally ambiguous thing. You may annoy other spectators, but more importantly, you may annoy the players. If you're running out of options, try metering for the brightest parts of the field--those directly under the floodlights, for example, and focus your camera there. Or, limit yourself to capturing the slower moments. If you don't have a fast lens, these may be your only options--either that, or miss photographing the game altogether.
Let's take a look at the third shot:
See those streaks in the grass? Compare them to the way the ground looks in the other two images. That's motion blur, too, but it's the kind of motion blur you get from camera shake. We use the term "camera shake" to describe motion blur that is caused by an unsteady hand. That's not your fault--it's simply impossible for any human being to hold a camera completely still once you get to those slower shutter speeds. Camera shake is amplified by the length of your lens--long, telephoto lenses are particularly vulnerable to camera shake at slow shutter speeds because they magnify it. They are also heavier and more difficult to keep steady.
How to fix it
Camera shake can be corrected in the same way that motion blur is corrected--with a faster shutter speed. As a general rule, you want to use a shutter speed that is at least the same number as the length of your lens. 1/200th, for example, if you're using a 200mm lens. However you also have regular motion blur to consider, so that may not be enough--you'll still need to bump up your shutter speed to 1/500 for that football game.
That's why you often see sports photographers with tripods--sometimes it's the only way to keep the camera and a very long lens steady enough to prevent camera shake, especially when the light is fading and you're already shooting as fast as you can, at a high ISO. Keep in mind that the tripod doesn't prevent all kinds of motion blur, just camera shake. You may still get some trails off your players if you're shooting slower than 1/500.
Other causes of blurry photos: Depth of field
Hey you! by Flickr user rolleh
It's worth mentioning that other common cause of blurry photos--depth of field that is too shallow for your subject. You will commonly see this when shooting subjects that have a lot of dimension at very large apertures (vs. flatter subjects such as the graffiti art on a wall, for example). Shallow depth of field can be a good thing, but not when you end up losing focus on all or part of your subject. In this situation, you need to pay attention to your aperture (the larger the f-number, the more depth of field you'll have) and adjust it according to how much of your subject needs to be in focus. If you don't want to use the aperture setting, you can use a preset--landscape mode will give you large depth of field, while portrait mode will give you a shallower one.
Blur is a monster that threatens all of us photographers, but the good news is we can keep it at bay with a simple understanding of what causes it and how to avoid it. It's always a good idea to examine the EXIF data for images that went wrong as well as those that went right--do this enough and you'll have a pretty good feel for the blurry monster and how to banish it.
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