120 film is medium format roll film. It is the next step up from 35mm and has been in production since roughly 1903. The film itself is wider than 35mm, the negatives are much bigger, and it loads completely differently to the 35mm canister most people start with. There is no rewinding. You wind from one spool to another, and at the end you tape the roll shut and send it off for developing.
That is the whole thing in a paragraph. The rest of this article is the practical detail, because almost everyone moving from 35mm to medium format has the same handful of questions and they all sound silly to ask until someone has answered them.
A bit of history
Roll film as a format came in around the turn of the century, late 19th into early 20th. 116 film came first by a few years and 120 followed in 1903 or thereabouts. “120” is not a measurement, by the way. It is the designation Kodak gave the format. The same way “35mm” is technically called 135. People assume 120 means 120 millimetres wide. It does not. The actual film width is 61 millimetres.
I mention this because it confuses people, and the language we use for film formats is genuinely a bit sloppy.
What is in the box
A roll of 120 film does not come in a canister. It comes in a sealed paper or foil wrapper inside a small box. When you open the wrapper you find a tightly wound roll of black backing paper with a piece of tape holding the end down, and on the outside of the roll it usually says UNEXPOSED.
![PLACEHOLDER: an unopened roll of 120 next to its wrapper and box]
The first time I held one of these I thought the matte black backing paper itself was the light-sensitive part. It is not. The backing paper is just paper. The actual film, the emulsion, is taped to the inside of the paper somewhere along the roll. You will only encounter it once you have wound through the leader.
![PLACEHOLDER: a partially unrolled 120 film showing backing paper at the start with the actual film emulsion taped to it further along]
The film and the backing paper are taped together quite securely. If you develop your own film and need to unroll a 120 to load it onto a developing spool, you will discover that the tape is reluctant to come off. That is by design. The backing paper protects the film from accidental light exposure during loading and unloading, and you really do want them stuck together until the moment you separate them in a dark bag.
How to tell if your camera takes 120
If you have inherited a camera and you are not sure what film it takes, open the back and look inside.
If you see a row of small teeth, called sprockets, running along the top and bottom of where the film sits, it takes 35mm. The sprockets engage with the sprocket holes punched along the edges of 35mm film, which is how the camera knows how far to advance for each frame. 120 film has no sprocket holes, so 120 cameras have no sprockets.
![PLACEHOLDER: inside of a 35mm camera showing sprockets]
If you see two empty spool-shaped spaces with no sprockets, and the spaces look like they would hold something about the diameter of a thumb and the length of your palm, it takes 120 (or possibly another roll format, like 127). One side is where the fresh film goes. The other side, called the take-up side, is where the film winds onto an empty spool as you shoot.
![PLACEHOLDER: inside of a medium format camera, showing the supply spool space, the take-up spool space, and the wind-on knob]
There is no rewinding mechanism on a 120 camera. The film goes one way only.
The take-up spool, which confuses everybody
Inside every 120 camera there should be an empty spool. This is the take-up spool. It is identical to the spool the new film comes wound on. There are not two different kinds of spool. They are just spools.
Here is how the cycle works:
- You buy a new film. It is wound on a spool, with backing paper around it, and the whole thing is taped at the loose end.
- You open the camera. There should be an empty spool on the take-up side, left over from the last roll someone shot.
- You put the new film on the supply side and feed the leader across to the take-up spool.
- As you shoot and wind on, the film transfers from the supply spool to the take-up spool. The supply spool slowly empties, the take-up spool slowly fills.
- At the end of the roll, your exposed film is now fully wound onto what was the empty take-up spool.
- You take that out, tape it shut, and send it off for developing.
- The now-empty spool that the new film came on becomes your next take-up spool. You move it across to the take-up side.
- New film goes in the supply side. Repeat.
You only ever need one extra spool, and your camera comes with it. Spools do not get sent back from the developing lab. They get recycled into the next roll you buy. If you start developing your own film, you will accumulate dozens of these things. They are not precious.
The wind-on knob on a 120 camera is always on the take-up side, because that is the side doing the pulling. Often the knob lifts or pulls out to let you drop the empty spool in. The exact mechanism varies by camera.
How do you know how far to wind on
This is the question I get asked most. There are two answers depending on which camera you have.
Method one: arrow markers and a click stop
Modern medium format cameras have a marker inside, often a red dot or a small triangle, near where the film is loaded. Your job when loading is to wind the film leader (the backing paper) across from the supply spool to the take-up spool until you see arrows printed on the backing paper. You line those arrows up with the red mark, close the back, and then wind on. The camera advances the film a precise distance and stops, often with an audible click, when it reaches frame one. From there, the camera handles frame spacing for the rest of the roll.
The Yashica 635 works this way. So does the Bronica S2A. So does any properly engineered medium format camera from the 1950s onwards.
![PLACEHOLDER: loading sequence on the Yashica 635, showing the arrows on the backing paper lined up with the red dot inside the camera]
Method two: the red window
Older and simpler cameras do not have any internal frame counting. They have a small red window cut into the back of the camera, usually covered by a sliding shutter you can close when not winding on.
What you see through that window is the printed numbering on the backing paper of the film. As you wind on, the backing paper passes the window, and the numbers go past in sequence. When the number “1” appears in the window, you are on frame one. Take the picture. Wind on until “2” appears. And so on.
The Agfa Isolette uses this method. So does the Kershaw 110, and pretty much every box camera ever made.
![PLACEHOLDER: the red window on the back of an Agfa Isolette with a number visible through it]
Why are there three rows of numbers on the backing paper
This trips people up. If you unroll a length of 120 backing paper you will see not one but three sets of numbers running along it. Top row, middle row, bottom row. The middle row counts to 12. The top row counts to 16. The bottom row counts to 8.
That is because 120 film can be shot at three common frame sizes:
- 645 (6cm by 4.5cm) gives you 16 shots per roll. Top row of numbers.
- 6x6 (6cm by 6cm) gives you 12 shots per roll. Middle row of numbers.
- 6x9 (6cm by 9cm) gives you 8 shots per roll. Bottom row of numbers.
The red window on the back of your camera is positioned to show whichever row corresponds to your camera’s frame size. A 6x6 camera (Yashica 635, Bronica S2A, Isolette) has its window in the middle. A 6x9 box camera (Brownie Hawkeye, Agfa Synchro Box) has its window lower down. A 645 camera would have its window on the opposite side. Each camera was built to expose a specific frame size and the window placement is part of the design.
![PLACEHOLDER: a length of 120 backing paper laid flat, showing the three rows of numbers and how they correspond to the three frame sizes]
There can be other frame sizes too (6x7, 6x12, 6x17) but those three are the common ones.
Finishing the roll
This is the bit that catches people out, because the muscle memory from 35mm is to rewind at the end.
You do not rewind 120 film. You keep winding in the same direction.
When you have taken your last frame (12 if you are shooting 6x6, 8 if you are shooting 6x9, 16 if you are shooting 645), keep winding on. The numbered section of the backing paper will pass through, then there will be a length of plain backing paper, and then you will feel the tension change as the film pulls clear of the supply spool. Keep winding. The whole roll, film and backing paper, will now be wound onto the take-up spool.
When the loose end of the backing paper comes off the supply spool, keep winding a bit more so the loose end winds around the take-up spool. Then take the take-up spool out of the camera.
What you have in your hand is the whole roll, exposed film and backing paper, wound tight, with a sticky tab on the outside.
The sticky tab varies by brand. Ilford films have a tab you have to lick to activate the glue. Some other brands have a peel-and-stick tab. Either way, fold the tab over, pull the roll as tight as you can, and seal it. Try not to do this under a bright light. The roll should feel firm. Loose winding is the most common cause of light leaks on developed film, so a few extra seconds of tension at this stage saves frames.
![PLACEHOLDER: hands sealing a finished roll of 120, sticky tab being folded over and pressed down]
The sticker on the tab will say EXPOSED on it, so you can tell which end is which. Drop the sealed roll in a light-proof container or back in its original box, and that is what you send off for developing.
Light sensitivity, which is worth a word
120 film is more sensitive to accidental light exposure than 35mm. With 35mm, the canister itself protects the unexposed film. With 120, all the protection is the backing paper, which is paper. So a few habits worth getting into:
- Load and unload in subdued light, not in direct sun.
- Always wind tight at the end of the roll.
- Keep finished rolls in a light-proof box until they go to the lab.
I have not personally had problems with light leaks from poor sealing, but I have heard from plenty of people who have. The fix is always the same. Wind it tighter next time.
Other roll film formats you might come across
If you have inherited an old camera, you may discover it takes something other than 120. The other format still in production is 127. It looks superficially like 120, but smaller.
![PLACEHOLDER: 120 film next to 127 film, side by side, showing the size difference]
127 is 40mm wide and most 127 cameras shoot a 4x4 frame, smaller than 6x6 but larger than 35mm. The loading mechanism is the same as 120: backing paper, take-up spool, no rewinding. It still gets made, although by far fewer manufacturers than 120, and you will pay a bit more for it.
Other dead formats you might find a camera for include 116, 620, and 220. 620 is particularly worth knowing about because it uses the same film as 120, just on a slightly thinner spool. You can re-spool 120 onto 620 spools yourself in a dark bag if you have an old 620 camera you want to use. Many people do.
Don’t overthink it
That is genuinely the most important thing. 120 is not difficult. It is different from 35mm and it takes five minutes to get your head around the fact that you wind from one spool to the other and seal the roll at the end instead of rewinding. Once that has clicked, the rest is just practice.
If you are sitting on the fence about trying medium format, the cameras have come down massively in price over the last twenty years and there is genuinely never been a better time to get started. Pick something simple and cheap and go and waste some film learning what you are doing.