A film holder is a flat, rigid two-sided frame designed to securely hold individual sheets of film for use with large format cameras. Each side of the holder accommodates a single sheet of film, allowing two sheets to be loaded into one holder - one on each side - making it possible to make two separate exposures without needing to reload between shots.
Film holders are loaded in a darkroom or changing bag, where sheets of film are carefully slid into each side of the holder and held in place by retaining guides. Each side is sealed with a removable dark slide - a thin, opaque panel that protects the film from light. When the holder is inserted into the camera and the photographer is ready to make an exposure, the dark slide is withdrawn, the shot is taken, and the dark slide is reinserted to protect the exposed film. A notch or marking system on the dark slide allows the photographer to distinguish between unexposed and exposed sheets.
Film holders are available in sizes corresponding to the most common large format film dimensions, including 5x4 inches and 10x8 inches. They are an essential piece of equipment for large format photography, requiring careful handling and thorough cleaning to prevent dust and debris from settling on the film surface and affecting image quality.