Why is aperture backwards??

[CarterFrost245]

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 (https://www.youtube.com/watch?v=fpdxMUWF0k0). 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???

[Vaughn]

The f/stop value is derived from an equation: It is the focal length divided by the diameter of entrance pupil. Pretty simple, but it can get complicated with some lenses and where to exactly measure the entrance pupil which is not always the same as the aperture.

It allows comparisons across focal lengths and aperture sizes without have to reference both every time one meters. Makes them easier to use. It is just the way the maths work out.

[Tin Can]

Fractions

[Drew Bedo]

Think of it like fractions: 1/3 of a Pizza is a LARGER portion than 1/8 of a Pizza.

If that does not help you understand the inverse relationship, some one else here will probably explain the math . . . .by chapter and verse . . .with reference to the natural logarithm of 2 (ln2). . . . .or perhaps it is the square root of 2.

[Drew Bedo]

Now: Will someone describe how to determine the exact dat of mardi Grass for any year by making specific reference to the phases of the moon and the Vernal Equinox?

[Alan Klein]

Explains https://expertphotography.com/understanding-fstops-stops-in-photography-exposure/

[sharktooth]

Well, it was erutrepa for the longest time ...... then Fuji cancelled it.

[Drew Bedo]

I apologize for the condescending response to a valid question form a new commer.

CarterFrost: Check your PMs please.

[Tracy Storer]

As others have said: the "f/#" is a ratio of opening size to focal length. (simplistically, usingd in the same units of measure) A smaller opening "goes into" the focal length more times than a large opening. I hope that is clear enough.


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 (https://www.youtube.com/watch?v=fpdxMUWF0k0). 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???

[Doremus Scudder]

Just to add a point of interest for the OP maybe:

The "f" in the f/8, etc. is the focal length of whatever lens your using. Replace that with the actual focal length of a particular lens and you get a division problem, e.g., 150mm/8 = 18.75, which is the actual size of the entrance pupil at that aperture setting. As you can see, 150mm/4 is larger: 37.5, and 150mm/16 is going to be smaller: 9.375.

Also, f/8 on two different focal-length lenses will come out differently. 150mm/8 = 18.75, 300mm/8 = 37.5. You can see that the longer focal length lens has a larger-size aperture at the same f-stop. This larger aperture will let in more light, but the fact that the longer lens has to be farther from the film to focus dims that extra light before it reaches the film and exactly compensates for it so that f/8 = f/8 as far as exposure goes for lenses of different focal lengths.

Best,

Doremus

[Maris Rusis]

The first time focal ratios were explained to me they were called F.Stops. The bigger the number the more light stopping power the aperture setting had.

[wsit]

For a 5.6 lens, Largest Aperture = focal_length/5.6. Hence f/5.6 is the common notation derived from maths

[Drew Wiley]

Aperture backwards? Wouldn't that be, "erurtrepa" ?

[Alan Klein]

Substitute a 1 for the f and it will all make sense.
f/1.4 1/1.4

f/2 1/2

f/4 1/4

f/5.6 1/5.6

f/8 1/8

f/11 1/11

f/16 1/16


etc.

[Vaughn]

What strange gods of optics declared that the the closer the camera is to an object, the further the lens has to be from the film for the object to be in focus?!!!!!

[Kiwi7475]

What strange gods of optics declared that the the closer the camera is to an object, the further the lens has to be from the film for the object to be in focus?!!!!!

This is a very interesting observation. If it were the opposite, then landscape photography wouldn’t be possible as the further away the camera is from the object, the further the lens would have to be from the film (in this opposite logic situation). So focusing to infinity would be difficult. So it has to be the other way. Otherwise we wouldn’t have working eyes. I guess you could say life could exist without vision. But not this forum. Ergo, since this forum exists..... :-)

[Drew Bedo]

Strange inverse natural laws indeed . . .

Youth is wasted on the young!
No good deed goes unpunished.
Virtue is its own revenge.

[ic-racer]

Don't feel bad, ISO is backwards, a higher number when less exposure is needed; wire gauge is backwards, a larger number is smaller wire, Shore value is backwards, a larger number is less compliant; color temperature is backwards, a hotter temperature is COOLER light; sandpaper is backwards, a higher number is smaller grit; springs are backwards, cut in half and it is twice as strong; A 10.5T electric motor is more powerful than a 25.5T motor; in vehicle dynamics a higher roll center produces less roll; and many others....

[Alan Klein]

Don't feel bad, ISO is backwards, a higher number when less exposure is needed; wire gauge is backwards, a larger number is smaller wire, Shore value is backwards, a larger number is less compliant; color temperature is backwards, a hotter temperature is COOLER light; sandpaper is backwards, a higher number is smaller grit; springs are backwards, cut in half and it is twice as strong; A 10.5T electric motor is more powerful than a 25.5T motor; in vehicle dynamics a higher roll center produces less roll; and many others....

Too bad age isn't like that.:(

[Tin Can]

Live your life backwards?

What happens when we move the studio light farther away?

[sharktooth]

Why do the folks here always take such a backwards and upside down perspective on things?

[Vaughn]

Just upside down...or downside up...but never backwards. Although all my carbon prints are printed 'backwards'.

[sharktooth]

..... and negative. Always so negative on everything.

[Vaughn]

:cool: