16 mm microfilm was used to store reduced-size photographs of documents that can then be viewed in a microfilm reader that magnifies the image to a readable size. 16 mm microfilm was generally used to store images of documents that were A3, A4, or Letter size, or even smaller sizes such as bank cheques or betting slips, whereas 35 mm microfilm tended to be used for larger documents such as newspapers or engineering drawings.
16 mm microfilm was first used commercially to take pictures of bank cheques, and a machine called the Checkograph was introduced in 1925 for this purpose. The 16 mm film format was relatively new at this stage, having been introduced in 1923.
The film itself is unperforated, and may have one continuous strip of images (simplex) or two lines of images where the front and back need to be stored together (duplex). It generally comes in lengths of 100 feet, 130 feet or 215 feet. Film in 215 foot lengths was thinner and tended to be used for duplex microfilming of documents such as bank cheques, insurance documents or and medical forms.
The film could be stored on an open reel, or it could be housed inside a cartridge.