The photogram

The photogram is the immediate result of a constellation of light, three-dimensional object and photosensitive material. Hereby the object is in partial contact with, or in a relative proximity to, the photosensitive material. In other words, there is no optical system between object and photosensitive surface. Processes of light-bending or refraction are at best caused by the objects themselves.
All two-dimensional electromagnetic receptors function theoretically as photosensitive material. A source of light can be used as well as invisible rays such as microwaves, infrared light or x-rays.
Conceptually, the photogram as a kind of light imprint differs fundamentally from lens-based photography. By its immediacy, its quality as index caused by the potential contact and the reversion of distance relationships, the photogram relates more to imprint techniques and shadow phenomena.

Or to make it short: The photogram is a highly differentiated shadow picture fixed directly on a light sensitive surface.

Das Photogramm

Das Photogramm hält eine unmittelbare Konstellation von Licht, dreidimensionalem Objekt und lichtempfindlichem Material fest. Der Gegenstand befindet sich hierbei in teilweisem Kontakt bzw. in relativer Nähe zum lichtempfindlichen Material. D.h. kein optisches System ist zwischen Objekt und lichtemfindlichem Material dazwischen geschaltet, Prozesse der Beugung oder der Brechung gehen höchstens vom Objekt selber aus. Als lichtempfindliches Material fungieren theoretisch alle flächigen elektromagnetischen Rezeptoren. Als "Lichtquelle" kommen auch nicht sichtbare Strahlen, wie beispielsweise Infrarot oder Röntgenstrahlen in Frage.

Konzeptionell unterscheidet sich das Photogramm als eine Art Lichtabdruck grundlegend von der linsenoptischen Photographie! Durch seine durch den potentiellen Kontakt bedingte Indexikalität und die Umkehrung des Distanzverhältnisses weist es vielmehr mediale Bezüge zum Abdruck und Schattenerscheinungen auf.

Oder um es kurz zu machen: Das Photogramm ist eine hochdifferenenziertes Schattenbild, das direkt auf einer lichtempfindlichen Oberfläche fixiert festgehalten wird.

Derivates of the photogram

The following techniques often subsumed as photograms, but do not consort with a narrow definition of photogram.

Luminogram

The luminogram (lat. lumen - light) only works with light. Objects are not used. Light is modulated by filters, patterns or motion. Sometimes the photographical surface itself plays the role of an object beeing e.g. bent, torn or knittered.

Chemigram

This technique simply uses just the chemical substance of a photo paper to create pictures. The silvergelatine is mainly modified not by light but by different chemicals. The chemicals are e.g. dropped or put on by a brush. There often exists a combined technique: A yet exposed paper is just developed or fixed partially. A conventional b/w-paper than results in different tones.
But the emulsion also can be modified by a large range of metallic salts and couplers. Even "completed" chemigrams are very dynamic. The tones often change by the influence of light, temperature and humidity, especially when they are not fixed or chemicals remain on the surface.
But also colour papers react. Especially organical substances like enzymes can have a immens influence on the emulsion.
Sometimes the emulsion is physically modified by scratching into the gelatine or even by burning (brulage) parts of the paper.
A lot of chemigrams have a strong painted character.

"Love" by Adam Fuss is photogram and chemigram as well: The enzymes of the bunny's entrails reacted with the colour paper.

Cliché verre

A cliché verre is a contact or enlarged print of a 2-dimensional object. It uses for example painted transparent papers, stencils, scratched glass plates or hand-modified negatives. Because of its 2-dimensionality it differs a lot from the photogram.

Thanks to Ted Green for the English translation!

 
Late cliché verre from 1874 by its inventor Camille Corot.

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