Surface sheen refers to the reflectivity of a print’s surface. It is an especially important attribute of photographic materials, which can range from matte to glossy with a great number of variations in between.
A print’s surface sheen can be classified by the way it reflects incident light, which is the light shining down on the object. The smoother the print’s surface, the more the light will be reflected directly along an angle equal to the angle of incidence. Light reflected at an angle equal to the incident light is called specular. A glossy surface will exhibit a strong specular reflection, while a matte surface will diffuse most or all of the incident light. A semi-gloss surface will reflect a mixture of both specular and diffuse light depending on the texture of the surface.
This can be demonstrated by reflecting a small, bright light source off the surface of a print, as in the images below. In the glossy print, a bright spot appears indicating that most of the light has reflected directly back to the viewer. As print surfaces progress from glossy to semi-gloss to matte, the bright spot spreads until no evidence of it remains in the matte print.
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| Glossy | Semi-gloss | Matte |
Technically, when measuring gloss, there are only three categories: glossy, semi-gloss, and matte. But even within these three, there are finer, incremental degrees of gloss. This allows manufacturers to create new pseudo-categories, such as luster, pearl, semi-matte, etc., to differentiate the items within their own product lines, as well as those from other manufacturers. However, there are no standards for these descriptions, so one manufacturer’s pearl may be another’s luster in terms of actual appearance.