The light source is usually an actinic bulb internal or external to the device[1] Commercial contact printers or process cameras usually use a pump-operated vacuum frame where the original and the photosensitive surface are pressed together against a flat glass by a grooved rubber mat connected to the vacuum source.
There are some models with internal light source constructed as a closed box, in which one or more lamps illuminate the negative through an opal or frosted glass.
The emulsion reacts depending on the amount of light received, for that reason it is important to make some tests for determining the exposure time.
The contact copier is used today, particularly in the areas hobbyist, for the photoengraving of prototype printed circuit boards (PCBs) before being sent to production (artisanal creation ).
Substantially similar to the contact printer used in photography, this variant usually uses ultraviolet lamps to impress a copper base specifically pre-sensitized.
Burned by exposure to light parts reproduce patterns drawn on a transparent photolith film on a pre-sensitized plate (epoxy or Bakelite).
Photolith film printed parts (usually black), inserted between the light source and the pre-sensitized plate, protect the varnish from the UV.