F-stops and apertureĪ lens, fully stopped down. The scale of F-stops is a geometric sequence of numbers: the sequence of the powers of the square root of 2. At ISO 400, it multiplies everything by 4 - and so on. At ISO 200, it’ll take your light measurements and multiply them by 2 (because it used half the shutter speed in its exposure calculation). When you’re shooting at ISO 100, your camera will use the light capture data as-is. These days, it refers to the sensitivity of your light sensor (or rather, a multiplication factor done by your camera’s processing chips). ISO deals with light sensitivity in the old days, we’d talk about film speeds of a certain ISO. The same goes for 1/100 and 1/200 - the former is half as fast as the latter. As I hinted at before, they are both pretty intuitive: A 2 second shutter speed means that the shutter is open twice as long as a 1 second shutter speed. ISO and Shutter speedsīefore we dive into aperture-land, let’s take a look at shutter speeds. In other words: if you shoot a photo at 1/100 second, f/4 and ISO 200, you would get exactly the same brightness in your photo if you halved the ISO and doubled the shutter speed (so 1/50 second and ISO 100) or the other way around (1/200 second shutter speed and ISO 400). That is you can use two different sets of exposure settings, that let the same amount of light onto your light sensor. ![]() ![]() It’s sort of important to know what ‘half the aperture’ is of any given aperture, because if you’re shooting in Manual mode (you’re not still shooting in automatic modes, are you?!), you can use something called ‘synonymous exposures’.
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