Monday, July 16, 2012
My Pictures Are Blurry, But What Kind Of Blur Is It?—07/16/12
Diagnosing blur is the first step to fixing it
|This Article Features Photo Zoom|
1. Motion blur. A fast-moving subject travels quickly across the camera sensor and that increases the odds of motion blur. This is perhaps the most commonly used blur in storytelling: because it occurs more with faster motion, it’s used to denote motion as well. When used correctly, motion blur becomes the photographer’s storytelling ally. If you don’t want to see motion blur, though, use a faster shutter speed. Start at 1/125th and get faster as needed.
2. Camera shake. Caused by a handheld shaky camera. The best way to eliminate this is to use a tripod, or a faster shutter speed—at least as fast as the focal length of the lens. With camera on a tripod, especially a tripod in conjunction with a cable release, your hands can't shake the camera at the moment of exposure. If you don’t have a cable release, use your camera’s self-timer to get your hands off the lens at the critical moment.
3. Long lens blur. Technically this is just camera shake, but I'm breaking it out as a separate item because it's the blur that's caused specifically by the long telephoto lens you're using. The rule of thumb I alluded to above? It’s based on the focal length of your camera. Got a 250mm lens? Use a shutter speed of at least 1/250th. 1000mm lens? 1/1000th or faster will minimize lens blur caused by camera shake amplified with a long lens.
4. Night blur. A fill flash illuminates the subject and a long exposure leaves trails of blur behind them. This is actually function of motion blur and a long shutter speed combination, but it doesn’t seem to make sense because the flash should freeze the subject, right? This is true, but only if the shutter speed is fast enough, or the ambient light is low enough, to prevent any ambient illumination from registering on the sensor and creating this nighttime motion blur. Eliminate it with a faster shutter speed, although this will also eliminate ambient exposure that can be helpful for painting a fuller picture. Instead, try setting your flash to rear-curtain sync so that any blur will trail from a frozen subject, rather than oddly occurring in front of it.
5. Focus blur. Perhaps the most common, least fixable (that is, unless you catch it in time), and most annoying type of blur is from poor focus. You missed your focus and ruined your shot. Sometimes slow or underperforming autofocus is to blame, sometimes it’s shutter lag, and other times it’s operator error. The key is to maximize your chances: if your subject is sitting still, or if you’re shooting in really low light, why not use manual focus to ensure your shot is tack sharp? If the subject is moving faster than your hand-eye coordination can cope with, consider a pro-style SLR with superfast autofocus that’s designed to prevent the blur that comes from missed focus. Or prefocus on a given spot and wait for your subject to reach it.
6. Depth of field. While this one’s related to focus blur, I’m separating it out anyway, because sometimes elements in a scene should be in focus but aren’t, not because the focus point was poor but because the depth of field wasn’t great enough. A product shot, for instance, should usually show the product sharp from front to back. If it’s not, if only part of the product is in focus, then even though the focus point may have been ideal, the depth of field clearly was not. A smaller aperture increases your odds of sharpness by maximizing the depth of field throughout a scene.
8. Dirty blur. A dirty filter or smudged lens can create smudgy, hazy blur. This is technically a variation on lens flare, as the light entering the lens is scattered and confused by the dirt on the front of the lens. The good news is preventing it is simple: keep your lenses and filters clean!
9. Crop blur. I know I'm getting crazy because there's no such thing as "crop blur." But stick with me for a moment. The picture my wife was inquiring about had exactly this issue. She had cropped a wide horizontal shot into much tighter vertical. The resulting image comprised only 20% of the original image size, so she had effectively multiplied the scale five times—magnifying every tiny little image flaw and focus issue too. So while the image wasn't truly "blurry" in the strictest terms, it definitely didn't look as sharp and precise as it should once enlarged. And that, I have deemed, is crop blur.
10. Deliberate blur. I'm cheating on this one because I couldn't stand the idea of only nine types of blur, and I thought I should mention the fact that blur isn't always a bad thing. Blur can actually be a great tool for storytelling (portraying the speed of a subject) and for adding visual interest (making a beautiful image of streaks of light or even "camera toss" photos for abstract blur images). The same techniques used to prevent unintended blur from your pictures can be reversed and exaggerated to add deliberate, beautiful blurs to your photographs. Just be sure to hand-hold the camera at a slow shutter speed and photograph a moving subject while you're moving the camera and you're bound to create a blur-filled image every time.