There are two types of contact printer devices: step printers and continuous contact printers.

The contact printers are divided into two categories. The first is a 'continuous’ printer, which, quickly and without pause, moves both positive and negative film together in contact with each other in front of an exposure aperture. The second is an ‘intermittent’ or ‘step printer’, in which each frame pauses for an instant in front of a beam of light, which is then blocked by a shutter until the next frame is exposed.

This research focuses on continuous contact printers.

In a step printer (also called intermittent) contact printer, the film original and the unexposed film are brought together, emulsion-to-emulsion, on to a continuously rotating sprocket wheel. After forming a loop, they pass in close contact (to ensure good sharpness) through a tensioned gate in which an aperture, slightly larger than the original picture-area, admits light from the source, via a condenser lens. After forming a second loop below the gate the films pass under a take-up sprocket and then separate.

The two films are both pulled intermittently and synchronously through the gate by a claw mechanism (T). Whilst the films are being moved forward, the rotating shutter S obscures light from the printing aperture. Immediately the claw has completed the forward stroke, the open section of the shutter reveals the printing aperture and light is again exposes the films.

(Source: Brian Pritchard; http://www.brianpritchard.com/FAOL/contents/2604200faol/Foncd/TEXTS/sect_8/contactpridx8.html)

These printers have a curved gate so the curve tensions the two films and holds them in good contact.

The continuous contact printers have different variations. For example 'additive' (RGB) and 'subtractive' (MYC), 'dry gate' and 'wet gate', 'panel printers'.

This is one of the earliest and most successful models of continuous contact printers.