As far as I have read f-stop is a measure of the aperture. This affects the amount of area in the foreground and background which is in focus.
While having a look at the dynamic ranges of cameras I realised that it is also measured in f-stops. The more f-stops, the more the dynamic range — which means better Brightness:Darkness ratio in the photo.
Do these two "f-stops" mean the same thing? Does the aperture size control the dynamic range?
Also I read that f-stop or f-number=focal length/diameter of entrance pupil. When the f-stop is changed, does the focal length change or diameter of entrance pupil change?
Answer
Dynamic range is not measured in f-stops, it is measured in stops. A stop is often used to refer to a change that doubles the value or, in the case of cameras, the amount of light. Changing the aperture by one f-stop doubles to amount of light allowed in, so in the case of aperture, a stop is an f-stop. Similarly, cutting the shutter speed in half is a one stop change, however it is not an f-stop because it is not aperture.
When a camera is said to have 12 stops of dynamic range, it means that the brightest part of a scene can be 2^12 times brighter than the darkest part. (One stop is twice as bright, two stops is 4 times, etc).
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