Although it maybe a thing in the past, but Why is film sold @ 12, 20, 24 and 36 exposures?

Answer 1

I assume you are talking about 35mm? When I first started shooting film, there were only two sizes 20 and 36. Now there are more but I think as film use decreases, you will find only two again - a short and a long roll.

12 is just a short roll for people who don't want to wait until they have shot a lot of pictures before getting them developed. Most expensive to buy and have developed - per picture.

20 is the old standard roll, pretty much replaced by 24.

36 is still the standard for long rolls when you need to shoot a lot and don't want to change rolls frequently. Least expensive per picture to buy and have developed.

I think you can find some 40 picture lengths as well.

Norm

Answer 2

I used to load my own film from a 100' roll, as Ara57 mentioned. A canister would fit 44 frames before binding the film. We don't need no steenkin' 36 frame rolls!

Slide film was always 20 and 36 and print film was always 24 and 36. I always wondered why, too.

Answer 3

There are also 50 and 100 feet rolls of film for people who bulk load film themselves. In my lab, we mostly carry 24 exposure rolls now, our company has discontinued 12 and most 36. Too bad, I really prefer 36 exposure rolls. I order them now from B & H.