This thought came into my head during a photo walk this evening. When comparing actual surface area of film, do you get more from a roll of medium format or 35mm? I was shooting Ilford Delta 3200, a fairly expensive film. B&H sells a 36 shot roll of 35mm for $7.07 and a 120 roll for $4.69.

Clearly the 120 rolls is cheaper, but can only yield between 4 and 16 shots depending on the frame size. So the photos can come out to between $1/shot and roughly $0.29/shot. The figure for a 6×6 camera (12 shots) is $0.39/shot.

The 35mm on the other hand yields somewhere between 36 and 39 shots (unless you have a half frame or panoramic camera of some sort, but those are few and far between), so the cost per shot is about $0.20.

That makes each shot only about half the cost of a medium format shot. Not a far cry since you get better detail out of medium format, but these numbers still don’t answer the original question.

So let’s get to it. A 35mm frame is 24mm by 36mm, or 864 square mm. A 6×6 frame is actually 56mm by 56mm, or 3136 square mm.

So 864 square mm times 36 frames = 31104 square mm for 35mm film

And 3136 square mm times 12 frames = 37632 quare mm for 120 film

The surface area cost for 35mm then is $0.000227 per square mm, and is $0.000125 per square mm for 120 (Yeah, yeah, who cares about significant digits). This makes the total surface area cost of 120 roughly half of 35mm. So take your pick. Cost per frame is half for 35mm and cost per square mm of surface area is half for 120.

(This leaves out the fact that you may get a bad or missing frame every so often but maybe you need to learn to use your camera. This also leaves out the fact that most films don’t have such a price difference between 120 and 35mm. Maybe I’ll do a comparison of Tmax or Portra too.)