523 is 4x5. Get a film pack adapter for your camera and you are in business. The film pack should be wrapped in foil and you unwrap it and put the metal cartridge in the film pack adapter. The first paper tab is the safety paper for loading and you pull the paper tab out which uncovers sheet #1 in the pack. After each exposure, replace the darkslide and pull the tab for the sheet that you just exposed and the exposed sheet is moved to the back of the pack and the next sheet is ready for exposure. After the film has all been exposed you open the pack in the darkroom and you can process the film. Remember that the film base is thinner that regular sheet film.