Aperture values and shutter speeds Both the aperture and the shutter determine how much light reaches the film. Each has a range of settings that varies by one stop. In terms of light, f/5.6 permits twice as much light to reach the film as does f/8. In exactly the same way, a shutter speed of 1/60 sec., allows twice as much light to reach the film as does a speed of 1/125 sec. You always balance shutter speeds and aperture values against each other. For instance, let's say the correct exposure of a scene would be 1/250 sec. at f/5.6. You decide you want to increase the shutter speed to catch a moving subject, in order to do so, you must change the shutter speed to 1/500 sec. In order to keep the exposure correct, you have to adjust the aperture value by exactly the same amount. Thus, you must double the size of the aperture, increasing it by one stop to f/4. Since f/4 lets in twice as much light as does f/5.6, the exposure is still correct. Depth-of-Field Depth-of-Field refers to the zone of in-focus elements, from front to back of the main subject. Depth-of-Field varies inversely with the aperture opening. That is, a wide open (maximum aperture) lens at f/1.4 has very little depth-of-field. If you stop down the lens to f/16, then almost everything from front to back will be sharply in focus. << Back to Main . 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 10 . 11 .