A blog post by Darkroom 8 Team
A roll of 36 exposures of 35mm film’s length is around 165cm. A single frame is 36mm+- wide and there’s 2mm border between each of the frame. We take the total length of the film 165cm minus out each of the exposure frame size, broader, film leader and the length you load and wind the film when you’re ready to shoot so the rest of the length is approximately 36 exposures ready to shoot. If you receive less than 36 exposures you can read through our previous post to figure it out. Link: Facebook Link A Link: Facebook Link B
I think you have a small error in the assumptions for your calculation. The frame plus space for each picture is 36mm+2mm as per your drawing, giving a total of 38mm for each picture. Your calculation has been done with 36 + 2 + 2 as the divisor which is counting the space twice on all but 1 frame. Using 38mm instead of 40mm (as per your calculation) gives 43.4 frames in 1650mm, not 41 ie an excess of 7 frames not 5 as per your chart.
Kodak use 64.5 inches for a 36 exposure film = 1638mm which gives 43.1 frames per roll including allowance for loading. Technically the calculation should be:-
(1638-2)/38 = 43.05
2mm is subtracted from…