Why is aperture backwards??

RobertCarter365

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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 -
. 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???
 

thomasw

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Aperture gives depth of field. The higher numbered aperture settings give more depth of focus i.e., (more depth of field). Hence it is in that sense which the higher numbers do give more depth by squinting more :) Conversely the lower apertures like 1.4 etc give us less depth of field and a shallower focus... So think it of like that and the numbers do make sense...
 

silver creek

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F Stop is NOT backwards. It is the ratio of the lens opening to the focal length of the lens. So f22 means that the lens opening is 1/22 of the lens focal length. So the F stop is denominator of the fractional lens opening and the numerator is always the number "1" and is understood.

Furthermore each higher F stop (smaller opening) allows in 50% of the light of the lower F stop (larger opening) so the length of the exposure has to be doubled at each higher F stop. It is totally logical. This assumes that the film speed stays stable of course.
 

LOC

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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 -
. 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???
I’ll try to explain in simple terms as well.

Instead of a lens we’ll l use a watermelon for reference. If you divided a watermelon by 2 you would have two large pieces or F2 if you divided by 22 or F22 you would have 22 small pieces. Larger number but smaller pieces. So f2 small number but bigger lens opening. F22 large number but small opening (small pieces).
Aperture is the focal length divided by the F number. HTH
 

Ard

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I'll be honest. While I did notice this back when I bought that Minolta SRT-100 (that's been a while) I just accepted it, kinda like we drive on the right side of the road thing .

I'm gonna go with Henry being correct mathematically and I would expect no less from him, and Thomas offering the logical option. Me, I'll stick with what I said but acknowledge Silver's depth of knowledge in all things technical.
 

proheli

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I was about to say this is a magnificent thread, because after the OP, the first two posts explained, by those two Intelligent gentlemen, the precise crux of the matter- and for just a moment I felt enlightened. As they say, if you can’t explain it to your grandmother, then you don’t really know what you’re talking about, and those two gentlemen had done a perfectly, even for a grandmother- but then LOC started talking about watermelon, and Bumble told me I was driving on the wrong side of the road. Now I feel dumber than a toad that’s just jumped into a pot of boiling water. Nice job fellas.... lol
 

LOC

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F Stop is NOT backwards. It is the ratio of the lens opening to the focal length of the lens. So f22 means that the lens opening is 1/22 of the lens focal length. So the F stop is denominator of the fractional lens opening and the numerator is always the number "1" and is understood.
So 1/22 of a watermelon :p:cool:
 
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trev

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Lots of things get smaller as the numbers get larger, and I think it is commonly a division problem; bird shot, wire gauge, sheet metal gauge, crochet needles, thread sizes of screws, sewing thread sizes, a long list and I won't attempt to enumerate or explain all of them. with my memory, I probably couldn't, but the greater the number of pieces of anything, a pie or watermelon or __, the more pieces you have, so that #10 could be 1/10 of you pick it, #14 would be 1/14 of it. The numbers and standards we use today may have started in antiquity with units we no longer are familiar with.
 
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