Photography

Special Photography Techniques, Prefocusing

Prefocusing is a technique used for cameras with Auto Focus and Auto Exposure Modes. Half pressing the shutter release button will lock the Focus and Exposure to the best setting for the scene where the camera is pointed at. This technique is used for 2 main reasons: 1. to eliminate the focusing and exposure delay that the camera takes to calculate the proper settings for a certain scene; and 2. to allow the camera to attain a proper focus setting on a subject that is difficult to focus or to settle on a more appropriate exposure setting for a scene with unbalanced lighting.

In occasions where the action happens very quickly like in sports or wild life photography, prefocusing your camera will help to capture the actions without delay. The technique requires that you point the camera to the subject or at any object that is at the approximate distance where you expect the action to happen. Use the smallest allowable aperture opening to maximize the depth of field. This will give you an allowance for focusing errors when your subject suddenly moves away or closer to you when the action happens. A good example would be photographing a bird as it takes off, or a biker as he passes by, or a basketball player as he slams the ball to the ring. There is very little time to take these special moments and a slight delay is very costly.

Prefocusing is also useful when the camera's autocus algorithms fails due to poor lighting or if the scene simply does not allow the autofocus to hold on to anything. In this situation, point your camera to a different object that is approximately on the same distance and lighting as your main subject, Choose a subject that is easier to focus on like objects with high contrast vertical elements. Half press the shutter release button to lock the focus then without releasing the button, point the camera back to the main subject. Once the framing is correct, fully press the shutter release button to take the picture. This works for pre-setting both focus and exposure. Be aware though, that this technique may not be very effective for Macro photography due to the small depth of field. The smaller the depth of field, the more likely this technique will not work.