Polaroid Film Conversions

Single sheet •  Film holder •  Instax film

Using single Paper negatives

A Polaroid pack film camera can use paper negatives without modification just by loading the paper into an empty film cartridge, then loading it into the camera. However, using paper negatives in this way works best considering the following factors:

  1. The camera should be equiped with a tripod socket. This would necessitate using a camera with a metal body.
  2. Either the electric eye should use a compensating neutral density filter (depending on the speed setting/aperture used), or the electric eye should be taped with black tape and the exposure done manually with a cable release. For example, a 4 stop ND filter would be needed over the electric eye when using the 75ASA setting with a multigrade filter.
  3. Using photographic paper as negatives results in negatives with higher contrast. Contrast can be lowered by using multigrade paper with a 1/2 filter in front of the lens. This will lower the ISO to 3, and result in a more usable negative.
  4. Using paper negatives without modifying the camera will require the negative to be loaded in a dark bag or darkroom. If more than one picture per camera is needed, a dark bag will be needed on the field.
This process is explained in this video, and an example of the full process in demonstrated in this video.

Using paper negative film holders

A pack film camera can be converted to use a film holder, which in theory can hold either a paper or film negative. This will both require the camera back to be modified, and the construction of film holders. The advantage of this procedure is that you can take as many photos as you have film holders, without having to load the paper negatives in the dark. This is more suitable for field work.

Modifying the camera back for a film holder

Step 1: First, the pack retainer/light trap is removed. It's screwed in by two small philips screws, making this a reversible step, as long as you don't lose it!
Step 2: Next, the rivets holding the rollers are drilled out
Step 3: The rollers are removed by unbending the retainer making the camera quite a bit lighter.
Step 4: The tab door hinges are removed by prying out the hinges
Step 5: Then, the door hinges on the back are cut off using a dremel. This is the hardest part because it's irreversible. I ended up cutting off the whole bar, so that the film holder doesn't need to be inserted in the groove.
The camera is now ready to use a film holder.

Making a film holder:

Step 1: The film pack is made starting with a foam board, with matt board cut to make a paper well where the negative sits.
Step 2: Grooves need to be cut into some book board for the dark slide to move in. I found this to protect against light leaks the best. I made a makeshift table saw out of a dremel sitting on modelling clay, a few blocks of wood, and a table made of a piece of plastic. I just screwed the shoulder/guide on with the correct clearance. This step doesn't need to be done, but makes it much easier to cut the grooves in the book board at a consistent depth.
Step 3: This made cutting the grooves into the book board far easier than doing it by hand. I did have to hold the dremel, since it's just sitting on modelling clay and could move a bit. This generated lots of smoke! But the grooves came out straight and consistent in depth.
Step 4: The dark slide guides with the grooves are mounted on the film holder with glue.
Step 5: A piece of felt is glued to the opening, the dark slide is cut out of bristle board, and a piece of hard plastic is taped at the opening to hold down the dark slide to seal out light leaks. Be sure to tape it down firmly.
Step 6: The finished film holder is double sided, which makes it just about the size of a Polaroid film pack. The darkslide grooves should be painted matt black to avoid light transmission.

Using a paper negative holder:

Step 1: The film holder is loaded into the camera by placing the back dark slide through the slit and carefully lowering the holder and pack into the camera. This is where your precision film pack holder building skills matter. Hopefully it fits snugly.
Step 2: When ready to take a photo, the dark slide is removed, but not all of the way. Draw a mark on the dark slide to show when it clears the negative. If you pull it out all of the way, you won't be able to get it back in again easily, if at all. After the dark slide is removed, take the photo and replace the dark slide.
Step 3: Develop the paper negative. This is the first test negative.
This is a demonstration of using the film holder outside. This is the ultimate test for light leaks. I ended up having to put a piece of foam on the door to help press the film holder in place to help prevent light leaks.

Converting a Polaroid pack film camera to use an Instax wide back

This will require one Instax wide camera and one Polaroid pack film camera. The Polaroid camera should have the extra exposure settings which allows it to be set for 300 ASA, so that metering with Instax film is possible. It may be possible to use any camera by setting it to 3000 ASA and using a 2 (or 3) stop ND filter over the electric eye. I found that exposing with the 300 ASA setting is pretty close since these cameras are getting old and often need exposure compensation of 1 mark toward lighten anyway because of the aging electric eye. The procedure is described in this video. Preparing the Instax back to be used for this purpose is shown in this video.

This operation involves taking the Instax camera apart and removing the electronic guts, leaving just the motor, gears, and rollers. The lens body also needs to be cut off with a hacksaw blade or other tool. Then, the back is removed from the Polaroid camera by drilling out the 4 rivets holding it on. The battery is removed and the wires trimmed (they will be connected to the Instax battery later). Then, the left side of the camera is cut off leaving just the top curve. The ridges on left and bottom sides are cut off so the Instax back can be mounted as close to the film plane as possible. And the bottom plate is cut to the tripod socket to facilitate mounting the back.

The Instax back is wired as follows: The negative battery wire is soldered to the top terminal of the motor. The other wire from the motor is soldered to one of the terminals of the micro switch. Keep the existing wires attached to the micro switch. The positive battery terminal is soldered to the other micro switch terminal. This will cause the motor to advance the film out of the rollers until the micro switch turns off by the depression in the cam. Unfortunately, the motor sometimes advances the cam so it turns on the switch again, so the depression in the cam will need to be lengthened on the leading side to turn off the motor a bit earlier.

Then, the wires from the shutter button are wired in parallel to the micro switch. Pressing the shutter will kick start the motor, activating the micro switch and ejecting the film. The carbon dot under the rubber shutter is replaced with a piece of aluminum foil for a better contact.

Then, craft closed cell black foam is cut to size to fit inside the Polaroid and a hole is cut to the size of the Instax film. The foam I had is about 2mm thick, so I cut three sheets to stack between the Polaroid and the Instax back. The last sheet is cut bigger, making it protrude out of the bottom of the camera to provide a light seal between the rollers and the outside world. I found I had to mount the back at the bottom left edge of the film plane. Since Instax film is the same width, but 1/2" shorter than Polaroid film, this means the picture will be what appears in the top right of the viewfinder. The image will be cropped a little on the left, and about 15% on the bottom.

A positive wire is soldered onto the Instax battery terminal one cell from the end to give 4.5 volts for the Polaroid camera. Solder it 2 cells from the end for newer Polaroids that take only 3 volts. This eliminates the need for a separate battery for the Polaroid camera. Extend the leads around the motor, and put the Instax back together, screwing the back cover to the motor assembly, then mount the back to the camera. I mounted it using a cut tin can, drilling holes in the metal tabs cut from the can. You'll need a small drill bit to drill holes for the screws into the Polaroid and the Instax back. Strap the back onto the camera using the small screws you removed when taking out the Instax guts. I strapped it on the right side, at the top left, and bent a can around the bottom plate and wrapped it around the handle. The metal straps were covered with hockey tape. Be sure to press down on the back while screwing the straps down to prevent light leaks. I cut the top off of the front cover of the Instax to help prevent light leaks in the roller assembly and mounted that to the instax as well.

Since the film plane is around 6mm farther back than it should be, I cut another stop in the top of the scissor assembly which controls the focus. Put the camera on a surface, focus to infinity, then push down on the top of the scissors and retract the lens assembly 6mm and mark the location of the pin which engages the top focusing bar. Cut two notches so the pin clicks into place when extending the lens. Once clicked into place, the lens will focus fine at infinity. When focused at its closest, the camera will be around 1/2" too close to the subject, but the aperture will be set at f/17.5 or f/32, which should make it in focus.

The portrait attachment works when focused on infinity, and when focused at its closest setting, will be around an inch too close to the subject. Check the focus against the rangefinder by covering the electric eye and opening the shutter and inserting a ground glass at the film plane. Once in focus, check against the rangefinder.

Counting the exposures can be done with a piece of paper with 10 tabs cut into it, taped onto the back. One tab is ripped off when a photo is ejected.

Single sheet •  Film holder •  Instax film