Those of us that own a DSLR or a top end compact camera will have noticed The letters, P, A, S, and M as will as an AUTO setting on the top of their camera. These represent programs that force the camera into doing what you want. The most popular is the AUTO- for Automatic Exposure. This setting chooses a medium high shutter speed for blur free pictures and also adjusts the aperture for a correct exposure. For most situations, this will do the job even though there are other combinations that will deliver a better picture.

P stands for Programmed Exposure and enables the user to change the shutter speed up or down in small increments without affecting the overall exposure. It does this by adjusting the aperture to compensate for a higher or lower shutter speed. Turning off the camera will of course remove the temporary setting. This option is handy when photographing a variably moving subject, such as sports, windy conditions for nature photography and photographing children.

‘A’ will bring up the Aperture Priority mode. By locking in a specific aperture, you are insuring that a needed shallow or deep field of focus will be an important feature of your picture. A shallow depth of field is handy for giving a busy background a Gaussian blur to a portrait or a nature study. This works best with a medium telephoto setting or longer. The deep field of focus is handy in extending the sharp range of focus to include near and far subjects in the picture. With the camera on a tripod or in bright light, the Auto setting will choose a high shutter speed and a relatively large opening. When a small aperture is needed for a deep field of focus, the A setting locks in a large or small opening for the desired result. The speed setting automatically adjusts for the correct exposure, so be sure to check the speed chosen by the camera since in low light, the speed could be longer than recommended for hand holding.

‘S’ stands for Shutter, the device that determines how long the exposure will last. There are many situations where a certain shutter speed has been found to be successful. Football game photos need a telephoto setting of 200 to 600 mm and a shutter speed of 1/250th or higher. Locking in a preferred shutter speed will insure a reasonably sharp action photo. Special motion effects call for a slower speed, say 1/5th of a second for slow moving subjects to 1/60th for a faster moving subject. You pan with the moving object to capture the feeling of the motion. In low light scenes, a certain shutter speed can be locked into the camera in order to prevent the camera from dipping down into a slow shutter speed for a ‘proper’ exposure. Some underexposure can be handled later in the computer but a blurry photo is useless.