The language used to describe silver gelatin prints revolves around four main attributes: paper tint, thickness, texture, and surface sheen. These characteristics are advertised subjectively in paper manufacturers’ descriptions using terms such as “warm”, “double weight”, “smooth” or “glossy”. But what do these terms really mean when side by side comparisons of prints denoted as “glossy” by their respective manufacturers exhibit a striking visual difference in surface sheen? A need to quantify these terms was apparent, and Paul Messier delivers with a repeatable, interoperable, and non-invasive protocol which he presented during the Saturday afternoon photography session at AIC’s 43rd Annual Meeting.
The protocol for obtaining measurements of thickness, paper tint, and surface sheen is fairly straightforward and employs tools well-known to conservators and scientists to collect the data. A micrometer measures thickness of the paper in millimeters; a glossmeter records the surface sheen in gloss units; and a spectrophotometer calculates the paper tint (highlights) using L*a*b* values. Quantifying texture, however, was not as simple, so Messier challenged teams from several universities to come up with a characterization algorithm based on images of the surface of photographic papers under the magnification in raking light. Using area-scale fractal analysis, the teams were able to meet his request and translate the 2-D images into information about the 3-D surface texture of silver gelatin papers from Messier’s extensive personal collection.
Once the four values described above are calculated, Messier gives them context by plotting them on a diagram based on percentile within each category. A diamond-shaped field is created with texture represented on top, thickness to the right, surface sheen on the bottom, and paper tint on the left (see image below). So called “practical” papers (smooth, glossy, neutral white, and single weight) tend to have points lying near the middle of the diagram while more “expressive” papers ( rough, matte, war m-toned, and thick ) have points towards the outer edges. These diagrams are useful for comparing prints across collections, interpreting artist’s intent, dating, and matching paper type and manufacturers to a growing database of known papers evaluated in this way.
The first large scale project using this method was carried out by Messier and his team to characterize prints in the Thomas Walther collection at the Museum of Modern Art and then compare them to prints made from the same negative at Museum of Fine Arts, Houston. Messier’s essay on this subject in MoMA’s Object: Photo website and publication is titled Image Isn’t Everything: Revealing Affinities across Collections through the Language of the Photographic Print (see link below). In addition to essay, the website also provides a clear description of the Messier’s protocol and includes specifications about the equipment and setup. Broader applications for this data are still being discovered, and the protocol is currently being used by the Center for Creative Photography to map the gelatin silver papers used by Harry Callahan. With this, Mesier presents a working method for the objective analysis of basic paper characteristics which still “honors and preserves the language that photographers knew and used.”
Link to Essay: http://www.moma.org/interactives/objectphoto/assets/essays/Messier.pdf