|10-02-2010, 09:55 AM||#1|
Join Date: Aug 2006
Location: The Woodlands, TX
Why Your Pictures Are Blurry
Some questions that I get asked often are "why are my pictures blurry?" and "how do you get your pictures so sharp?". There are two main things that affect sharpness - focus and motion.
Things that are in focus appear sharp and things that are out of focus appear blurry. The more out of focus they are, the blurrier they appear. You almost always want your subject, especially their eyes, in focus. Stuff in your picture that isn't your subject can be out of focus. In fact, having everything but your subject blurry helps make your subject stand out and look sharper.
Cameras have lots of different way to focus. I find that I get the best focus for non-moving objects by putting my camera on a tripod, using LiveView, and setting the mangification to 10x. They I carefully manually focus on my subject. The downsides to this approach are that they require a tripod or steady surface, the subject can't be moving, it takes time to set up, and I need my reading glasses to see the LCD.
For me, the next best technique is for me to put an autofocus point directly over the most critical focus element (usually the subject's eye) and tell my autofocus to focus on that. If there isn't an AF point in the right place, I shift my camera until the AF point is where I want it, lock the focus, and then recompose for the composition I wanted. This trick works OK, but if you have really shallow DOF, the act of recomposing can sometimes be enough to cause you to misfocus.
Leaving all of the AF points on works OK if your subject is the closest thing to you. It can be a bit dangerous. I've had lots of shots ruined because the AF focused on someone's hand in front of their body or even on the tip of their nose. If you are using a P&S or shooting with a smaller aperture, this usually isn't a problem.
No all AF points are the same. They work by looking for contrast (a dark and light area side-by-side). Some AF points are more sensitive than others. Some can see side-by-side or top-and-bottom contrast areas while others can only see one or the other. Usually, the central AF point is the most sensitive and flexible.
Many cameras have two modes for autofocus - locking and continuous. Locking autofocus gets it's subject in focus and then holds that focus position. If your subject moves after focus is locked, you'll be out of focus again. With continuous, the camera keeps focusing until the shutter is released. That works great for moving subjects, but doesn't work well if you do the lock focus/re-compose technique.
Many cameras give you a hybrid option by letting you move the AF activator off of the shutter button and onto a different button. In that mode, you hold the AF button to engage continuous AF. Whenever you want to "lock" focus, you just release the AF button. That technique gives you the best of both worlds, but it is harder to get used to and confuses the heck out of anyone else that tries to use your camera.
The other big cause of blurriness is motion. A picture does not capture a single instant; it captures a very brief period of time. Things can move during that time and cause blurriness. There are two types of motion to worry about - camera motion and subject motion.
The biggest risk factor for motion blurriness is your shutter speed. That's the amount of time that your shutter is open when you take a picture. The longer your shutter speed, the more problems you will have with motion blur. You can get faster shutter speeds by opening your aperture wider or increasing your ISO.
The easiest problem to fix is camera motion. The best way to stop camera motion is to use a tripod. If you don't have one convenient, rest your camera on something solid. If possible trigger your shutter without touching the camera. Use a remote shutter release (wired or wireless) or use the time function on your camera.
If you really want the sharpest shot possible and you are using an SLR, lock up your mirror. When you look through the viewfinder of an SLR, you are seeing the image reflected off of a mirror in front of the sensor. When the shutter is about to open, the mirror swings out of the way. Moving the mirror makes your camera shake just a bit. You can move the mirror out of the way before you shoot by either using the mirror lockup function on your camera or by switching it to LiveView (which also moves the mirror).
If you can't stabilize your camera with a tripod or by resting it on something, the next best thing is an image stabilizer. Some cameras stabilize the image by moving the sensor and others work by moving elements in the lens. Each technique has its advantages and disadvantages. I don't want to start a debate over their relative merits. Just use whatever image stabilizer is available to you if you.
At fast enough shutter speeds, a tripod or stabilizer is not really necessary or noticeably helpful. The old rule of thumb was that you really wanted some form of stabilization if the inverse of your shutter speed was lower than the focal length of your lens. In other words, if you were using a 100mm lens, you would want a shutter speed of 1/100 or faster. This is just a rule of thumb and varies by shooter. It was meant to be the minimum speed at which you had a reasonably good chance of a reasonably sharp picture. The truth is that a tripod will usually improve your sharpness even if you are shooting at double or even quadruple this speed.
It really helps to learn how to best hold your camera while shooting. Good hand holding technique will significantly improve your steadiness. For an SLR, always support your lens from the bottom with your left hand. Keep your elbows tucked in. Relax. Shoot between breaths.
Many people say that they get better shots if they fire a burst. The first shot is often a bit blurrier than the second or third shot in the burst.
No matter how well you stabilize your camera, that won't help with subject motion. If your subject is moving, you must have a higher shutter speed to keep them from blurring. How high a shutter speed depends on the direction that they are moving, how fast they are moving, and how far away they are. A good general rule if you want a running person sharp is to shoot with a shutter speed twice as fast as the reciprocal of your 35mm equivalent focal length. So if you are using a 200mm lens on a full frame camera to shoot people running about, keep your shutter speed at 1/400 or faster. If you are shooting with a 200mm on an APS-C camera, keep your shutter speed at 1/600 or faster.
If you want get a fast enough shutter speed, another option is to move the camera with your subject. You can either stay in one spot and keep panning your camera as your subject moves past, or you can move along with your subject. A good WDW example would be a picture taken of someone sitting next to you on a fast ride. Even though you might be going 40mph, you are both moving together. This can give you a picture where your subject is reasonably sharp but they background has lots of motion blur. Just don't expect too many of these types of shots to be extremely sharp.
Another option for stopping motion with longer shutter speeds is to use a flash. The flash itself is almost instantaneous, so it will do a good job of stopping apparent motion. If the subject is in a dark area and lit entirely by the flash, this works great. If the subject is lit partially by the flash and partially by ambient light, they'll still look somewhat blurry. The moment of the flash will look sharp with some ghosting for the rest of the time. Set your camera to use rear or second curtain flash sync for situations like this. That way, they sharp part will be at the end of the movement rather than at the beginning.
If you can't get a fast enough shutter speed, use a flash, or move along with your subject, you're in trouble. You can try shouting "freeze", but if it works at all it usually leaves you with subjects looking surprised rather than happy. Another technique is to drug your subjects with something like Ritalin, but I'm not advocating that either.
If you get blurry pictures, study them to understand why. What was your shutter speed? How steady was your camera? Was the right thing in focus? If you can't figure it out, post the picture here and ask.
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