contact print

The Contact copy is a special imaging method. If a proposal by the direct contact with the substrate of an imaging method copies, one speaks of a contact copy.

• 2.1 Traditional methods
• 2.2 blueprints
• 2.3 Lichtpausverfahren

Modern Photography

Nowadays contact copies have two main applications: Artistic representations and copies of image carriers. Examples:

• Slide Duplication
• Motion picture films are reproduced by contact printing. When the optical sound track it will be copied in contact.

Contact Sheet

If by a contact printing process produces a photo from a movie, it is called a contact sheet.

Contact prints were mainly at the time of glass photographic plates the usual method to obtain a positive.

A contact sheet of negatives is usually the first quality assessment of the images of a film negative. In the contact sheet, the negative is placed directly on the photo paper and exposed this short.

Contact sheets of small-and medium-format negatives are usually also made ​​for archival purposes; the corresponding leaves are often stored together with the negatives. At even smaller formats (Pocket film, etc. ), however, have contact sheets usually no purpose, since the image content would qualify even with a magnifying glass any more.

Photocopy

If the contact printing method, a photo of images and documents produced, one speaks of photocopy.

When photocopying a little sensitive and high-contrast ( "hard ") is placed black and white photo paper with the light-sensitive side on the document to be copied and the two are exposed by the photo paper side. Through the reflection of the original, a negative image of the document is produced on the photographic paper after its development and fixation. In the second step produces a positive image of the document from the negative in the same manner.

Photocopies of archive when acid-free and thus archive grade paper used.

Photogram

When photogram objects are placed directly on film or photo paper and exposed.

Technology

In the photo lab technology contact copy available that work with vacuum and are equipped with various light sources.

Quality characteristics

Because of the unavoidable stray light in the shadow enhancers are often flat at magnifications or underexposed the lights: On contact withdrawal of large negatives from professional cameras own positives that differ in the rule of positive result of magnifications. In a contact sheet stray light can not develop. The quality of a contact sheet can therefore be significantly better. Agfa widespread until the 1960s, a special photo paper for contact sheets under the name " Lupex " whose extinction curve and sensitivity significantly differed from photo paper for enlargements. Other film manufacturers had such papers in the range.

Historical Photography

Different methods of contact copy are several hundred years old.

Traditional methods

A known already from the middle ages simple form of contact print is the nature print. Later, other methods emerged as the salt print.

Blueprints

• Cyanotype functions on the basis of iron salts. There is no development required, fixation by washing with water
• Diazo functions on the basis of an azo dye. The development is carried out in ammonia vapor, there is no fixing necessary (depending on the emulsion caused blue copies).

Use to contact exposure both methods ultraviolet light or sunlight. The light sensitivity of the material used is small, it can therefore be used without a darkroom.

Lichtpausverfahren

Lichtpausverfahren generate photochemically from a transparent or thin paper template a copy on special paper using the principle of contact copy. In contrast to photocopy but is used as an emulsion no silver. The resolution is low. Diazotype is traditionally referred to as the blueprint.