Your camera has to have the right combination of light + exposure time to = proper exposure. Your shutter speed and your lens aperture work together to give you the correct exposure as determined by either you or your camera. (more on how to determine best exposure later). This means that if you change shutter speed you must also change f/stop (aperture) in order to keep the same exposure value.
Lets assume that your camera’s light meter tells you that 1/60 second exposure time @ f/11 will give you the correct exposure. If you were to place the shutter speeds and the f/stops (aperture) on a scale the following combinations would also give you exactly the same exposure value.
1/15 – 1/30 – 1/60 – 1/125 – 1/250 – 1/500 – 1/1000 f/22 – f/16 — f/11 – – f/8 — f/5.6 — – f/4 – — f/2.8
Deciding which combination to use depends primarily on which is more important to the photographer, shutter speed or depth of field for this particular picture. Remember however, if you change shutter speed setting (or aperture) you must change the corresponding aperture (or shutter speed) setting to keep the same exposure value.
For example. If your camera light meter tells you that 1/60 second at f/11 will give you the correct exposure and you want to increase your shutter speed to 1/250 sec you must open your lens aperture to f/5.6 in order to keep the same exposure value. You have to let in more light to compensate for the fact that you’re now cutting the amount of time that the light will be exposed on the film or pixals.
Remember, f/5.6 is two stops wider than f/11 and 1/250 sec is two shutter speed settings from 1/60. This is the easiest way to remember this as opposed to thinking; “hmm…1/250 is four times faster than 1/60 so I need four times as much light….” The math is much easier if you simply remember if you change your shutter speed by x number of clicks you must change the aperature the same number. And vice versa obviously.
Faster shutter speeds means you need more light. Less light means you need slower shutter speeds.
Text: Tutorialtub.com
Photo: Pilottage