Change the shutter speed to adjust how much light is allowed into the camera for a certain length of time. Camera’s shutter speeds are calculated in fractions of seconds, which are usually 1/1000, 1/500, 1/250, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2 and 1.

Calculating the correct shutter speed to use is a matter of understanding geometric sequence. As you increase the speed from 1/1000 toward 1 second, each increase multiplies the amount of light entering the lens by a factor of 2.