Focusing Your SLR Camera Tips

When I was an absolute beginner at photography, I did not understand how to properly focus my SLR camera.  Prior to falling in love with photography, I was the usual snapshot taker with a compact point and shoot camera.  Auto mode produced “good enough” focusing for the purpose of my family snapshots and 4 x 6 prints.  Once I crossed the line into taking photography seriously as an art form and profession, this of course changed.  There is no such thing as “good enough” now.

Many times an image can look perfectly fine when viewed at a very small resolution.  However, the same image when viewed larger or at 100% resolution can be distressingly out of focus.  This became especially important to me when I began shooting textures for stock.  In order for a texture stock image to pass inspection, every bit of the photo must be completely in focus, and the only way to determine this is if it is carefully inspected at 100% resolution.  It’s not possible to know if perfect focus has been achieved by looking at the image on the LCD screen of your camera.

Autofocus on a SLR camera can be incredibly accurate and the best choice under most shooting situations.  Typically a camera auto-focuses with a system that is much like radar.  The camera itself sends out either a beam of infrared or an inaudible sound.  This beam bounces off the subject and is reflected back to a sensor in the camera, which then instructs the motors to move the lens.

There are definitely some drawbacks to using autofocus.  For example, most autofocus systems can’t focus through glass, a screen or on a distant scene.  Also, areas without detail such as a cloudless sky or a blank wall, as well as low light conditions, can be very difficult for autofocus to handle.

Digital SLR Autofocus Modes:

1. Focus lock – This is useful if you want to focus on someone’s face, or a specific point in a scene, but want this subject to be off to one side of the frame.  You can center the subject within the focusing mark seen in the viewfinder, press the shutter release button halfway, and then move the camera to compose the scene to your liking.  You can then press the shutter all the way down to finish taking the shot.  One thing to be careful of when using focus lock is maintaining proper exposure.  On some cameras, once you have locked focus, the exposure is automatically locked as well.
2. Continuous AF – The camera focuses continuously as you move it until you press the shutter release button.  This helps to shorten the lag time between pressing the shutter release and focusing.
3. Predictive AF – This mode is helpful when a subject is moving either toward or away from the camera at a fixed rate.  The camera predicts where the subject will actually be when the shutter is released.

Tips on Focusing:

1. The closer your subject is to the camera, the more attention that must be placed on focusing.  When your subject is far away, your focus can be off by a few feet but your image will still turn out acceptably sharp.  However, being only a few inches off with a close subject can throw your image noticeable out of focus.
2. If you are shooting a moving subject which is moving toward or away from you, it is useful to select a point and focus on it.  Once the subject reaches the point you have selected, press the shutter release button.
3. To bring both the foreground and background of a distant scene into focus, you will need to use a greater depth of field.  The smaller the aperture (higher number) the greater the depth of field.  Also, the shorter the focal length of your lens, the greater the depth of field at any setting.
4. To photograph  a texture a tripod is a necessity.  Once your camera is sturdily mounted on a tripod, set the ISO to 100 and the aperture to  f/11.  Carefully compose your shot and press the shutter release.
5. Use manual focus in low light situations where autofocus won’t work, or when trying to shoot through something like bars.  Manual focus will allow you to focus on your chosen subject.