Manual Work

Open Flames

Candles and fireplaces produce a great amount of infrared energy that can overwhelm the infrared sensor of a camera with an active auto-focus system, making it difficult for the camera to read the returning pulses. Of course, if the subject is the flame, it will work fine.

Low contrast subject

A problem for passive systems is large areas of solid or similar colors that have little or no contrast. When the colors in the subject are all the same or similar colors (such as flat wall), the auto-focus mechanism may not be able to determine whether the subject is in focus.

Black or dark colors

Some materials (especially dark colors or black) can absorb the infrared pulses, confusing an active auto-focus.

Low light

Even though infrared pulses signals can work in the dark, if your camera uses passive auto-focus and you are shooting a low contrast subject in dim light, the camera may have difficulty determining the correct focus.

Subject too close

All camera have a minimum focusing distance, and if you are closer than the minimum distance the focusing motor will try several times to focus before stopping (to save battery)

Wrong subject

The auto-focus can be fooled by something that is either farther or closer than the subject you intended to be in focus.

Depth Of Field And How It Effects Focus

When you focus your camera on an object, you can be certain it will be focus, but the rest of the image may not be. The range in a photograph, from near to far, that appear to be in focus is called depth of field. In narrow depth of field (limited DOF), only a short distance in front of and behind the subject is in focus. A wide depth of field (extended DOF) means more distance in front of and behind the subject in focus. Controlling the depth of field can enhance a photo or create a cool effect. A narrow depth of field (limited DOF), can make the subject stands out.

Controlling The Depth Of Field

DOP of a photograph is controlled by the distance the subject is located from the camera and the aperture of the lens (measured in f-stops). Although several other factors control it as well, distance and f-stops have the greatest effect on DOF. The farther the subject is from the camera, the greater the DOF. As the lens focuses out to infinity, the DOF also become infinite. For closer work, f-stops narrows or widens the DOF. As the camera lens opened up (f-stops setting decreases), the DOF also increases.
Another way to decrease the DOF is to zoom out the lens to its maximum setting.

How Shutter Speed Relates To Focal Length

When you shoot a photo on a bright sunny day at the beach, (if you are in auto-mode) your camera will automatically increases the shutter speed to some very high setting, such as 1/1000 if a second.
If you zoomed out your camera to the maximum and your shutter speed is set to relatively slow speed (less than 1/125 of a second), you should consider stabilizing your camera.

When To Use A Steady Platform

You should consider using a steady platform for the following types of photography:
• Low-light photography


• Macro photography


• Still life


• Panoramas