Printer in which the raw stock is exposed while in contact with the original. Contact printers can be a ‘continuous’ or ‘step’ type. Machines for the printing of motion picture film by contact may be divided into two types, step printers and continuous printers.
In continous printers the negative and positive films are brought together in contact on a sprocket (or roller) and moved continuously and at a uniform speed across an illuminated aperture at which the exposure is made.
The leading edges of the perforations in both the negative and the positive films are engaged by teeth of the large sprocket and carried past the printing aperture as the sprocket revolves.
Contact between the two films is produced by bending the films longitudinally at the printing aperture, by the tension produced by the weight of the idler rollers at the top.
The sprocket is enclosed, so that light reaches the negative and positive films only at the printing aperture. Exposure is controlled by changing either the width of the aperture or the intensity of the illumination on the negative – usually the latter.
In step printers the negative and positive films are moved intermittently, as in the camera, and each frame is exposed as a unit while stationary in front of the printing light. A shutter placed in front of the printing aperture cuts off the light while the negative and positive film are being moved into position for the next exposure. The amount of exposure is usually controlled by altering the intensity of the light.
In a step printer the exposure is made when both films are at rest; consequently there can be no loss of definition in the print from movement of the films with respect to one another during the exposure.
In a continuous printer, however, both films are in motion during the exposure, and if the perforation pitch is not the same for both films, as is usually the case, it is necessary to compensate for the difference in the perforation pitch of the two films. This is taken care of by the curved gate of the printer.
The use of step printers for badly shrunken negatives may be justified in the interests of better definition. For printing from the sound negative, however, the only permissible type of printer is the continuous machine.