The Finer Points of Focus

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Most of the time, unless we’re trying to achieve some sort of differing photographic effect, photographers are shooting for tack-sharp pictures. Here are some tips for taking sharp and well-focussed pictures.

1. Stability is key. I’ve said it before and I’ll say it again. If you want to take a picture that is perfectly focused at every size and magnification, you’ll need to keep the camera stable. This means using a sturdy tripod (one that has a head strong enough to support your heaviest camera/lens combination), and a cable release or wireless remote shutter release. If you are using a lens with image stability capabilities, turn the IS feature off – the motor that activates the IS generates small vibrations which can throw off the focus of your image.

2. Learn how to use focus lock. Often times when trying to compose a picture, the camera’s auto-focus feature will focus on the center of the frame, which may not necessarily be the intended subject. While some of the more advanced digital camera systems have multiple points of focus visible through the viewfinder that the photographer can cycle through and choose at will, there is an easy way to use the focus lock if you’re short on time, or have a camera that does not have this feature. Look through the viewfinder and center the subject in the middle of the frame to use it as the focus point. Press the shutter halfway down to focus on the subject and “lock” the focus (you will typically see red lights flashing in the focus point boxes (refer to the below image), visible through the viewfinder when you press the shutter release halfway, which will tell you which point the camera is focusing on). Keep holding the shutter halfway down and recompose the shot to position the subject wherever you desire within the frame. Then press the shutter all the way down to take the picture.

3. Sometimes manual focus is better. Often times are own eyeballs are more trustworthy than the camera’s auto-focus feature. So don’t be afraid to switch to manual focus. If working in low light conditions, temporarily illuminate your subject with a flashlight so that you can see well enough to set the focus, before taking the picture. A tripod and remote shutter release or timer is particularly essential for sharp photographs when operating in dim lighting.

4. Use a fast shutter speed. Typically lenses focus best if you shoot at a shutter speed whose denominator is larger than the lens’ greatest focal length. So, for instance, if you are using a 50mm prime lens, shoot at speeds of 1/60 or faster. If you are using a 70-200mm zoom lens, shoot at 1/250 or faster. This is a great “rule of thumb”, though it doesn’t always apply in every circumstance. Also, remember to adjust your aperture to compensate for the shutter speed (the faster the shutter speed is, the larger the aperture needs to be in order to let as much light in as possible in the short amount of time the shutter is open). It may be helpful to shoot in aperture priority mode to dictate the desired depth of field you’re going for, and let the camera compensate for the required shutter speed.

5. Use the lowest ISO number possible for the circumstances. An ISO of 100 will generate less “noise” (or a grainy appearance) into the photograph than an ISO number of 800.

6. Clean your equipment. Though many digital SLR’s today have automatic sensor cleaning features, they are usually not enough to ensure the sensor is REALLY clean. The insides of a camera also have lots of reflective surfaces and mirrors that acquire dust and grime no matter how careful you are when you’re switching between lenses. Finally, lens components themselves can acquire dirt and smudges that can be hard to remove completely. Invest in some good cleaning kits for your camera, sensor, and lenses. Or if you prefer to let the professionals handle it (as I do), track down your local camera shop and, for a usually nominal fee, they will handle all of the cleaning for you. You would be amazed at how much your photographs will improve once you remove the dirt that you may not have even known was there.

Photo Credits (in order of appearance):
- “Gorillapod” by Stephen Mitchell on Flickr Creative Commons.
- “FS-3 Grid Focusing Screen” by cbmd on Flickr.
- “Focused” by KoshyK on Flickr Creative Commons.

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  • Brett

    If you want to get even more tack sharp, you can use mirror lock-up in combination with a tripod and a remote shutter release. If your camera has this feature, you'll compose your shot, set the mirror to up (this will block the viewfinder), then take your hands off the camera and use the shutter release to take the picture.

    Everything that moves during the exposure can cause tiny vibrations. If you're on a sturdy tripod, using a remote shutter release, and locking up the mirror, you've eliminated every vibration you can… from there it's only the shutter itself that is moving during the exposure, and there's no getting around that.

    Of course, you'll probably only need mirror lock-up if you're super paranoid about eliminating all vibration; most amateurs and semi-pros probably won't bother.