Kodak introduced the 828 film size for use with its Bantam camera series in 1935. Kodak quit selling 828 film in the mid-70s and then had offered only Kodacolor for several years. The 828 film size grew out of the realization by a Kodak designer that there was wasted resource in the 35mm format because of the area taken by the sprocket holes. The 828 format uses a 28 x 40 mm frame that provides an image about 30% larger than the 35mm format while uses the same width film stock.
The traditional way of dealing with this discontinued format has been to recycle spools and backing paper and reload them with stock from bulk, unperforated 35mm rolls. This works almost as well as the original 828 film stock, except that it was produced with one small sprocket hole every 40mm that engaged a pin that allowed automatic frame advance. I have described the conventional reloading operation below. Donald Miller has also shared some less conventional ideas for cutting down 120 film and backing paper, which has the advantage of offering a broader range of emulsions, including B&W, and avoiding worn 828 backing paper, albiet without some of the original features . If after reviewing any of these reloading procedures, you think it is beyond you and/or your resources, you can buy 828 film for $10-$17/roll.
most obvious reloading option is to use 35mm perforated film because of
its availability in single magazines or in bulk rolls of various lengths.
The use of perforated 35mm film has some limitations.
Spooling 828. Respooling procedures are essentially the same regardless of using perforated or unperforated stock. Respooling 828 is more challanging than 620, though some of the same techniques apply. Foremost is the precious 828 backing paper--it must be constantly recycled, and since it was thin to begin with, it must be carefully handled in spooling and developing operations. While the number of emulsions in unperforated film are limited, the selection of emulsions for standard 35mm is not. If you don't process your own film, you must get a pledge from your processor of his first born if he does not return your 828 spools and backing paper. Getting a roll of 828 processed will likely cost as much 135/36 rolls do, because it will have to be done by hand, so you really have to enjoy shooting with your Bantam to make this worthwhile.
Here is a sketch of the film configuration of rollfilm.
The goal is to cut a piece of perforated or unperforated 35mm film to the right length and attach it in the right place to the 828 backing paper.
Before Respooling. Film respooling requires the cleanest conditions to avoid dust specks on negatives and slides. Your work surface must be clean and chemical-free. Static electric charges form inversely to moisture content of the surrounding air, so dust problems for reloading and printing will increase with low humidity. A humidifier or vaporizer run for an hour or so before darkrom use is helpful. Those processing in darkened bathrooms might just run the shower for a few minutes. Taping several sheets of legal copier paper over your direct work space provides a clean surface! At a minimum, wash your hands and rinse them in hot water to remove skin oil and chemicals or, better, wear latex or cotton gloves that are free from substances. To the degree possible, handle film by the edges. In all winding operations, note that 828 spools have two unequal spindle slots--one that runs the length of the spool and the other that is about half that length, centered between the flanges. Backing paper should be threaded first though the longer of the slots. You will need a piece of masking or Scotch tape 1 inch long for each roll. You will have to break the seal on the front end of the backing paper. This may be the only identification of film type. Save and reseal it with Scotch tape or otherwise label the film type you have respooled.
Cutting the Film. 828 images are 28x40mm, with a 2mm interframe space, and about 15mm on each end, so we need a piece of 35mm film that is about 14 1/2 inches long. Here are a couple of techiques I have used.
Method A. Adjust the stop on your paper cutter to 14.5 inches or tape down a small piece of posterboard in that position. Method B: Take two pieces of 14.5 x 1.5-inch posterboard and tape them together on both sides with plastic packing tape to make a hinged template. You can use this to measure lengths of film, almost without touching the film surface. While I have sterile conditions set up around my paper cutter, I cut more strips than I will load that day and store them in a 35mm film canister sealed with black electrical tape. Better organized Bantam users will realize that if one canister is good, several are better. Cutting and storing film in high humidity can cause condensation when the film is frozen.
In rolling the film, the biggest challenge is to determine where on the 828 backing paper to begin winding the film, since you are winding it backwards and that end of the film is untaped. I put a piece of hopefully chemically inert Scotch tape with a texture different from the paper on the outside of backing paper at the point where the film should end during its normal winding operation. That also is a tactile hint in total darkness that I am winding the paper correctly backwards. You can start winding the backing paper on to the empty spool in room light if you have a supply of empty spools and backing paper. If you are removing an exposed roll and loading fresh film in the same operation, knowing backend from frontend gets dicier. Once you have tucked the backend of the film strip into the spool you are rewinding, keep sandwiching the film and backing paper until you come to the frontend of the film, then tape it to the backing paper with precut strips of 1 inch long tape. I have put Scotch tape on the inside of the backing paper at the taping point to reinforce the paper, since this is a stress point and 828 backing paper was paper, not the plastic composite used today on rollfilm. Reseal the respooled roll with tape or some label material that allows you to record the emulsion you've loaded. Remember, that 828 backing paper is very dear, so use materials that don't damage it.
Processing. Of course 828 can be processed in tanks that accept 35mm film. When composing, remember to mentally crop the image when shooting if you do not have an 828 negative carrier for your enlarger. Two 828 rolls will be about the equivalent of one 20-exposure 35mm roll when monitoring solutions.
Below is a listing of unperforated 35mm film available from two suppliers.