Graphics: The clearer picture, Part I

There's nothing quite like the feeling you get when you find that a special picture has been ruined by blurring. It's a surprisingly common problem, often aggravated by the huge range of features in digital cameras.

Luckily, it's possible to re--duce the occurrence of blurring by understanding its causes and adjusting your camera techniques. If the impact of blurring on your photograph is mild, a few solutions are also available within your graphics program - a topic I'll be covering next month. Keep this warning in mind: undoing the damage of blurring is hard work, with slim chances of success, so it's worth the effort avoiding the problem in the first place.

Types of blurring

The three main causes of blurring are poor focus, camera movement, and a fast-moving subject. If the image is blurred because the subject matter is travelling quickly - such as a speeding car - this is called motion blur. When blurring occurs due to the camera wobbling, it is generally called camera shake.

This leads to the first technique for avoiding motion blur and camera shake - use your camera's Shutter Priority or Manual mode to select a faster shutter speed. By now, you may be wondering why cameras don't always use the fastest possible speed. It's because there's a trade-off related to another part of the camera called the aperture. Without going into all the details, as the speed of the shutter increases, the aperture has to open wider to let in more light. The side effect of this process is that it makes it harder to focus the entire scene. It's a frustrating situation - as you try to reduce motion blur or camera shake, you increase the chance that your image is out of focus.

Focus blur

As the name suggests, focus blur occurs when a desired part of an image is out of focus. It's not all bad - sometimes blurring the background or other parts of the image can create interesting photographs. Assuming you want your subject matter in focus, the best step is to use pre-focus. Cameras that include this feature use a two-step shutter button: press it down halfway and the camera sets the exposure and autofocus; press it down completely and the shot is taken.

Cameras also tend to use a small point at the centre of the lens for calculating the area to focus. If this section is not pointing directly at your target subject, it may cause the camera to focus on other objects. It's a common problem when a person is standing to the side of the frame with a large vista in the background - the camera focuses at the horizon and the person comes out blurred. To avoid this, point the camera directly at the subject and half-press the shutter button to set the focus, then, with your finger still on the button and the focus locked, frame the image the way you want it and take the shot.

Finally, find out how your camera determines the focus. Most digital camera manuals will give some description of how to focus the image, and some allow you to focus manually. Likewise, it's important to learn how to change the shutter and aperture priorities (or manual settings). Digital cameras give you instant access to your photographs, but they can't turn back time - don't wait until an important event before trying to learn the various settings.

Tips For Avoiding Blurred Images

  • If light is low, try using the camera's shutter priority, usually depicted by an athlete icon. Be aware that you'll lose depth of field and increase the chance of poorly focused objects.
  • For bright sunny conditions where you want everything in focus, use the Aperture Priority setting (assuming the subject is not moving quickly).
  • If your camera supports it, experiment with a higher ISO setting (you'll find it in the setup menu). The trade-off here is that images may come out looking grainy, but you can use faster shutter speeds.
  • Remember that many digital cameras have shutter lag, and can take a second or two to actually take the shot. Press gently on the shutter button using your index finger, and keep still. There's no need to move or tilt your hands.
  • Use a lower zoom setting, which permits a wider aperture (more light) and reduces camera shake.
  • Try using a tripod or minipod, or resting the camera on a flat surface and using the timer; pressing the button can move the camera.
  • When light is poor, use a slightly faster shutter speed than the camera wants (only available if you camera has manual shutter control). Your picture may be a little dark, but this is far easier to correct than blurring.

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