Duplicate negative

A duplicate negative (jargon: Dupneg ) is a photographic replica of a photographic original, that is, the image of which has brightness values and / or complementary colors that are reversed compared to nature. Most of the time, the original is an exhibition positive , in photography a paper picture or slide , in cinematography a so-called screening copy . In contrast to the internegative or intermediate negative, it comes from an unfavorable or difficult to copy original, be it because of its mechanical condition or because of its strong contrast.

The duplicate negative plays the central role in traditional archive technology. Many of the pictures that you want to receive are only positive on paper or a cinema copy. By transferring the content to fresh film, if possible while eliminating all existing errors, technicians at a copier are trying to create a new generation from which fresh exhibition positives can be copied again, paper images or projection copies.

A duplicate negative of the photograph is generally a new take. The original is evenly illuminated, suitable film material is exposed with a camera with little to no reduction in size. The 1: 1 reproduction ratio allows fresh positives to be deducted from the duplicate negative using the inexpensive contact method.

With a few exceptions, a duplicate negative of the cinematography is created in the contact process . If, for example, the shrinkage of the starting film is too great, the mechanical guidance of the same must be separated from the transport of the raw film . Adapted film drives are used on the output side, and precision mechanisms are always used on the copy side. In such a case, of course, the imaging is done by an objective on a scale of 1: 1 with minor corrections. Another difficulty is that the original is warped, which can call into question the full-surface contact and thus a sharp duplicate.

In addition to the classic photographic method, duplicate negatives are also produced as film recordings of digital data obtained from scanning the original.

With the ongoing improvement of special duplicating film materials, the transmission of images has become so good that one can speak of almost lossless duplicates. In the black and white sector, grainless materials are in use, in the color sector the grain growth is very small. If the effort is justified, black and white color separations can also be used to perfectly duplicate color films. Laypeople do not recognize any difference between the original and a "duplicate".

literature

The microscopy. How and why? Edited by Gevaert Photo-Producten, NV, Mortsel, 1956