Things to consider ...
1. who is the artist ?
2. name of piece of art ? date ?
3. technique used ?
4. number of prints ?
The 70s marked the beginning of photography as a collectible art form. Photographers moved from printing unlimited copies, to the model used by lithographers. This is essentially a representation based on trust of how many prints are to be printed, and it relies on the honesty of photographers, their printers and galleries.
Prints are now typically (but not always) sold in series, with a defined end-point. Editions are usually between 3 and 15 prints, in various set sizes (small, medium, large format). Gallerist and photographers can decide to make the price increases when the prints are sold. The earliest prints are the least expensive, after which prices increase up to the end of the series.
Prices will also vary based on the size of the prints sold. There are usually two extra prints, not for sale but for the artist’s record: there are named Artist proof (AP) or Epreuve d’artiste (EP). These prints can however end up on the art market, especially if the artist is recognized after his or her death.
A photographer has more often an oral than a written engagement with a gallery insuring exclusivity in one country. Known photographers can have a gallery in several big cultural cities like London, NYC, Berlin, Milan… At an international art fair, his or her work could be presented simultaneously in a few galleries’ booths. The galleries keep track between themselves of the edition numbers and prices for available pieces.
Vintage prints refer to those printed at the time the artist was active, and are more valuable than reprints made later.
Printing & display techniques
The first decades of photography were very experimental and innovative. The earliest photographers, many of them French, used raw materials as egg white (albumen), salts or starch to fix images, first on paper, then on glass. It was a long, slow while until the discovery of the film process that allows a very easy and democratic use of photography.
Most photographers today use digital printing, even if they still use film photography. The negatives are scanned to print in professional studios. It is not possible to print the currently popular large, color formats in a darkroom.
Sometimes photos are backed with aluminum (‘contrecollé’) and they can also be face mounted to plexiglass, a technique and patented manufacturing process called a diasec. This adds brightness and depth to a photo, and is currently in vogue. BUT the plexiglass can be easily scratched and irreversibly damaged, which lowers the work’s value.
A concise introduction to the history of photography.
Here’s a quick historical timeline of developments in photography from photo.net.
A fun look at how art photographic movements map to major art trends.
Here’s a very good article on current trends in photography collecting, from Blouin ArtInfo.
A great glossary of photographic terms can be found at the Ansel Adams Gallery site. It’s useful to familiarize yourselves with them so you can better understand exactly what you’re buying.