In early days of photography, available shutter speeds were not standardized, though a typical sequence might have been 1⁄ 10 s, 1⁄ 25 s, 1⁄ 50 s, 1⁄ 100 s, 1⁄ 200 s and 1⁄ 500 s neither were apertures or film sensitivity (at least 3 different national standards existed). Short exposure times are sometimes called "fast", and long exposure times "slow".Īdjustments to the aperture need to be compensated by changes of the shutter speed to keep the same (right) exposure. Very long shutter speeds are used to intentionally blur a moving subject for effect. Very short shutter speeds can be used to freeze fast-moving subjects, for example at sporting events. In addition to its effect on exposure, the shutter speed changes the way movement appears in photographs. A shutter speed of 1⁄ 50 s with an f/4 aperture gives the same exposure value as a 1⁄ 100 s shutter speed with an f/2.8 aperture, and also the same exposure value as a 1⁄ 200 s shutter speed with an f/2 aperture, or 1⁄ 25 s at f/5.6.
For example, f/8 lets 4 times more light into the camera as f/16 does. Reducing the aperture size at multiples of one over the square root of two lets half as much light into the camera, usually at a predefined scale of f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and so on. According to exposure value formula, doubling the exposure time doubles the amount of light (subtracts 1 EV). Multiple combinations of shutter speed and f-number can give the same exposure value (E.V.). Too much light let into the camera results in an overly pale image (or "over-exposure") while too little light will result in an overly dark image (or "under-exposure"). This will achieve a good exposure when all the details of the scene are legible on the photograph. Once the sensitivity to light of the recording surface (either film or sensor) is set in numbers expressed in " ISOs" (ex: 200 ISO, 400 ISO), the light emitted by the scene photographed can be controlled through aperture and shutter-speed to match the film or sensor sensitivity to light. Exposure value (EV) is a quantity that accounts for the shutter speed and the f-number. Most people just learn the f/numbers off-by-heart without really understanding their meaning.The camera's shutter speed, the lens's aperture or f-stop, and the scene's luminance together determine the amount of light that reaches the film or sensor (the exposure).
This sound like a drag to calculate each time, and it is. If you wanted to let in 1-stop less light, you would multiply 5.6 by 1.4 to get 8, use f/8. So if you were using at f/5.6 and you wanted 1-stop more light, you would divide 5.6 by 1.4 to get about 4, so you would use f/4.
A change of 1-stop of light using aperture is called an f/stop. So, increasing the diameter of lens opening by 1.4 will let in 1-stop more light, and reducing it by 1.4 will let in 1-stop less! Just to make a little bit harder, the f/number is inversely proportional to the area, meaning the higher the f/number the less light it lets in.
WHAT DOES SHUTTER COUNT MEAN ISO
Unlike shutter speed and ISO where you can double or half to increase or decrease by 1-stop of light, for aperture it is in multiples of 1.4!!! This is because lenses are circular, so if you want to double to area of a circle you increase the diameter (and radius alike) by 1.4 (flashback to school maths anyone?). The aperture of a lens is denoted by an f/number, which corresponds to how much light the lens lets in. Up until now, it has been fairly straightforward, but alas, here we are with aperture.