Contact print
From Free net encyclopedia
A contact print is a photographic image produced from a film, usually a negative, occasionally from a film positive. The defining characteristic of a contact print is that the photographic result is made by exposing through the film original onto a light sensitive material pressed tightly to the film.
An exposure box device called a contact printer or a printing frame is used within a light controlled space called a darkroom.
One or more negatives are placed in intimate contact with a sheet of sensitized photographic paper. This is then placed, negative down, onto a top transparent glass plate of the exposure box. Within the box and below the top plate is a translucent light diffuser made from frosted glass. Below the diffuser is a switch controlled electric light source. A hinged top cover serves to keep the materials in close contact and to reduce or eliminate stray light into the darkroom.
The contact printer is used to expose the negative's image onto the paper for a few seconds, creating an invisible latent image in the paper. The operator may use a manual switch and count off the seconds or may control an electric timer switch.
With the black and white gelatin-silver process this may be done using a red "safelight" for darkroom illumination. The contact printer may also contain a safelight so that the negative may be examined before the photographic paper is laid upon it.
After exposure, the exposed paper is processed using chemicals to produce the final print.
Since this process produces neither enlargement nor reduction, the image on the paper print is exactly the same size as the image on the negative. Contact prints are used to produce proof sheets from entire rolls of 35mm negative (from 135 film cassettes) , and 120 (2 1/4 film rolls, to aid in the selection of images for further enlargement, and to aid in cataloging and identification. Using 120 roll film (once a common negative size for popular cameras), and larger film, contact prints are often used to produce the final print size. In medium and Large_format photography, contact prints are prized for their extreme fidelity to the negative, with exquisite detail that may be seen with the use of a magnifying glass. A disadvantage of contact prints for fine arts use is the laboriousness of modifying exposure selectively when contact printing (see the enlarger article).
When large format film is contact printed to create finished works, it is possible, but not easy to use local controls to interpret the image on the negative. "Burning" and "dodging" require painstaking work with photographic masks, or the use of a production contact printing machine (Arkay, Morse, Burke and James are manufacturors who made contact printing machines).
Contact printing machines are more elaborated devices than the more familiar and more widely available contact printing frames. They typically combine in a box the light source, intermediate glass stages, and a final glass stage for the negative and paper to be placed upon, and an elastic pressure plate to keep the negative and paper in tight contact. Dodging can be accomplished by means such as placing fine tissue paper on the intermediate glass stages between the light source and the negative/paper sandwitch to modify the exposure locally. The benefit to such time intensive techniques is the ability to then make multiple prints with negligible variation, and at full production speed.
Contact printing was also used at one time in photolithography and in printed circuit manufacturing.
The contact exposure process usually refers to a film negative used in conjunction with a printing paper, but the process may be used with any transparent or translucent original image printed by contact onto a light sensitive material. Negatives or positives on film or even paper may for various purposes be used to make contact exposures onto various films and papers. Intermediary products such as internegatives, interpositives, enlarged negatives, and contrast controlling masks, are often made using contact exposures.