Why is aperture backwards??
So, I get that larger f numbers like f/22 actually mean that it's a smaller opening and that smaller f number like f/2 is a big opening. I learned that thanks to a really helpful beginner video I just watched - this video. But my question is this...WHY is the size of the aperture backwards from the numbers. Shouldn't f/22 be a big aperture since it's a big number and f/2 should be a small aperture since it's a small number???
Suppose we have a 50mm focal length lens. If we have a big size hole – a big aperture, it might measure 25mm. So 50 divided by 25 gives us 2: the f/number is 2, which we write as f/2.
If the aperture is smaller, say, 3mm in diameter, 50 divided by 3 gives us about 16: the f/number reads f/16. As the hole is smaller, less light gets through. So f/16 is said to be a small aperture or small f/number.
That’s why you could get confused if you read about an aperture of 16 being smaller than 2: that does not make sense and is, in fact, wrong. A photographic aperture is written as ‘f/number’: it means the focal length divided by the aperture diameter. So f/16 is indeed smaller than f/2
Google is my Friend.
If the aperture is smaller, say, 3mm in diameter, 50 divided by 3 gives us about 16: the f/number reads f/16. As the hole is smaller, less light gets through. So f/16 is said to be a small aperture or small f/number.
That’s why you could get confused if you read about an aperture of 16 being smaller than 2: that does not make sense and is, in fact, wrong. A photographic aperture is written as ‘f/number’: it means the focal length divided by the aperture diameter. So f/16 is indeed smaller than f/2
Google is my Friend.
Think of it as a resistance like in an electric circuit.
As Cephus says - the F/ number is the focal length divided by the diameter of the aperture. For this reason a particular F number does not indicate a fixed size of aperture, the size varies according to the lens.
The F stop doesn't actually tell us how much light will reach the film or sensor, which is why the movie world uses T stops, where the f stop has been corrected to transmission losses.
F denotes a fraction calculation.
The larger the denominator the smaller the result of the division, thus smaller the iris hole.
The larger the denominator the smaller the result of the division, thus smaller the iris hole.
Quote:As they said ^
In other words, 1/2 is larger than 1/4
Those of us who have done any teaching will know that some students don't readily accept that fact and are only convinced by a demo of cake-cutting!
Reminded me of a brilliant illustration of that fact 'thewilliam2' I was trying to get a class to understand measuring and was using the illustration of 'hands. So I asked them to stretch their fingers out amd make a mark where the tip of their little finger came and where the tip of their thumb came and then to measure it with their rulers. I then asked them to get the measurement of two hands, which they did. But when I asked what the measurement of three hands would be there was silence until a little voice piped up 'I haven't got three hands miss'.
Thank you so much
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