Shutter/Aperture Priority

Some cameras have modes called shutter priority and aperture priority. These are not available in the basic point-and-shoot models but in some of the more advanced models. These modes are usually represented in the mode dial by S or Tv for shutter priority and A or Av depending on the manufacturers wish.

Shutter and Aperture priority modes are a sort of semi-automatic modes. In the fully-automatic mode, the camera will choose the shutter speed and the aperture value automatically depending on the exposure. These automatically chosen values cannot be changed or can be modified using a 'program-shift' feature that some cameras provide.

But now, in these modes, you have the option of choosing the shutter speed or the aperture value on your own and the camera will adjust the other parameter depending on the light and required exposure. For example, suppose the automatic setting requires an aperture of F/5.0 and shutter speed of 1/200s. Now, in the aperture priority mode, I set the aperture to F/2.8. Now the amount of light has increased because of the wider aperture. So correspondingly the shutter speed will be decreased to about, say 1/500s, by the camera, since it is in the aperture priority mode.

Similarly in the shutter priority mode, you are allowed to change the shutter speed value and the camera automatically chooses the best aperture value for a good exposure.

This might not sound very interesting during normal photography, but it makes for very simple shooting when shooting some creative photos.