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Walk into a camera store or browse film online and you will see the same emulsion sold in two versions: 135 and 120. Same name, same speed, very different rolls. If you are new to film, the numbers can be confusing, and buying the wrong one means a roll that will not fit your camera. This guide explains the difference between 35mm and 120 film, what each one is good for and how to choose.
What the numbers mean
135 is the film most people picture: 35mm film wound inside a small light tight metal cassette. 120 is roll film for medium format cameras, wound on a spool with a paper backing instead of a cassette. The numbers are format codes rather than measurements, and you will see both on the box and in film makers' data sheets.
Kodak is a good example. In the Portra 400 technical data sheet, Kodak lists the film in 135, 120 and sheet sizes, each with its own product code. Kodak Tri-X 400 is offered in 135 and 120 sizes too. When a film comes in both, the emulsion is the same family, but the format and the camera it fits are not.
35mm film (135)
35mm is the format of most point and shoot cameras, classic SLRs and nearly every new film camera you can buy today. The cassette protects the film while you load it, and Kodak recommends loading and unloading roll film cameras in subdued light. After the last frame, you rewind the film back into the cassette before opening the camera.
Why choose it:
- Cameras are everywhere. Our list of film cameras you can still buy new is all 35mm.
- More shots per roll. 35mm rolls are sold in longer lengths, so you get more frames before you need to reload.
- Compact. Small cameras and small rolls mean easy everyday carry.
- Scans and enlarges well. Kodak says Portra 400 offers extraordinary enlargement capability from a 35mm negative.
120 film
120 is the medium format roll. The film is much wider than 35mm, so each frame is larger. There is no cassette; the film is rolled together with a paper wrapper that keeps out light. Ilford's film FAQ explains that the frame numbers printed on that wrapper are read through the red window on the back of many cameras, which is how older and simpler cameras know where each frame starts.
Why choose it:
- A bigger negative. A larger frame captures more detail and smoother tones for the same film.
- Different frame shapes. Medium format cameras make frames in several sizes and shapes, from rectangles to perfect squares. The number of shots per roll depends on the frame size your camera makes, so check its manual.
- A slower pace. Fewer frames per roll makes every shot count.
There is a small technical difference in the film itself too. Kodak's data sheet lists the 120 version of Portra 400 on a 0.11mm acetate base and the 135 version on a 0.13mm acetate base. Kodak also says the 120 size can be retouched on both the base and emulsion side, while the 135 size should be retouched only on the emulsion side.
What stays the same
The emulsion and its look carry across formats. Portra 400 is Portra 400 whether it comes in a cassette or on a spool, with the same natural skin tones Kodak promises, and it is developed in the same Process C-41. Tri-X 400 has the same character in both sizes as well. Kodak's Tri-X data sheet even treats a 135-36 roll and a 120 roll the same way when calculating developer replenishment, which tells you each holds a similar amount of film to process.
Storage advice is the same too. Keep film cool, let refrigerated film warm up before opening the package to avoid condensation, and process it soon after you shoot. Kodak's warm up times differ slightly by size, with 120 rolls typically ready a little sooner than 135 magazines.
Which film to load
Whatever the format, the film choice is the fun part. For color, Kodak Portra 400 is a flexible favorite for people and travel. For black and white, Kodak Tri-X 400 is a classic that Kodak recommends for push processing. Both are sold in 135 and 120, so you can stay with a film you love even if you move up to medium format later.
Whichever format you pick, keep a note with each roll: the film, the camera and anything unusual about how you shot it. When the scans come back, those notes make it far easier to learn what worked and to repeat it on the next roll.
How to choose
- Check your camera first. The camera decides the format. A 35mm camera takes 135 only, and a medium format camera takes 120.
- New to film: start with 35mm. Cameras are easier to find, rolls are easier to load and you get more frames to learn with.
- Want maximum detail: move to 120 for the bigger negative.
- Shooting on the go: 35mm keeps everything small enough to carry daily.
If you would rather chase a film look digitally, our guide to Fujifilm film simulations is a good place to start.
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