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Why I did it
Recently I got some old Kodak camera's. These things are a nice piece of decoration, but it's way cooler to use such vintage camera. There is only one problem: old camera's use old film formats. The spools that fitted in my camera's where 120 and 620 spools. 120 spools are still available, but are pretty expensive. 620 spools are not even made anymore.
What I did
Some people use empty 620 spools to roll 120 film or modern 35mm film on it. But this process has to happen in complete darkness, and is time-consuming. Instead of doing this, I designed two parts that fit on a 35mm film-spool. These make the 35mm spool longer: as long as a 620 or a 120 spool. Depending on what adapter you used. In this way, you can easily fit a modern (and cheap(er)) 35mm film in an old camera.
The adapters are attached to this instructable as .stl-file. Feel free to take them to the 3D-printer!
How to use it
At this moment, I've made two different adapters: one for 120film camera's and one for 620film camera's. But I'm planning making an adapter for 127film camera's too. Using the adapter is very simple:
(1) Each adapter consists of two pieces. Because the 35mm film-spool isn't symmetrical, one of the pieces is a little bit bigger than the other one. Place them in such a way that the 35mm film is in the middle of the entirety.
(2) Use tape to attach the end of the 35mm film to an empty spool (normally there is always an empty spool in a camera. In the time these camera's were made, the film was transferred from the loaded spool to the empty spool. (More information on Wikipedia))
(3) Place both spools in the camera and close it. The place where the loaded spool has to be is often indicated on the inside of the camera.
(4) To know how many times you have to turn the wind knob after each photo, you divide the width of the exposed piece of film by the circumference of the spool (36mm for a 120spool and 25mm for a 620spool) You can wind the knob a little more to make sure there is a nice gap between each photo. Because the empty spool will become thicker with the film rolled on it, the gap between two photo's on your developed film will become bigger after each photo.
(5) When you shot as many pictures as possible on your film, it's time to wind the film back in it's cassette. You have to do this in COMPLETE darkness. Just open the camera, remove the adapter from the spool, and wind the film back in the cassette with a screwdriver. You can cut the last centimeter off the film, where you taped it on the empty spool. The film is now ready to get developed!
Some remarks ...
Using these adapters has some consequences. Some are positive, some are negative, some are just cool:
(1) I can't promise the adapter will fit in all camera's. You have to check the diameter of the 35mm casette with the free space in your camera. This will happen more frequently with 620 film camera's, because the 620 spool is a little smaller. Using the adapter in the Kodak Brownie Hawkeye is not possible, for example. But I'll definitely think about a solution!
(2) Using this adapter, you will expose the whole height (also the sprocket holes) of the 35mm film. The reason is that this film is not as high as the original film formats. For this reason, the upper and lower part of what you see in the viewfinder won't be on your film.
(3) Using this adapter, you can place the 35mm film with the back of the film faced to the lens hole. This will give you a redscale effect without any further modifications. To use the redscale effect in a modern 35mm film camera, or for more information about this effect, read this instructable.
(4) It's very important to do the rewinding of the film in complete darkness. Of course this is not ideal, but I don't know any alternatives.