The properties of a film-developer combination are usually described by various, more or less well-defined parameters. One of these is the film speed, a parameter that can be determined relatively easily both in practice and, together with the slope (gamma value), by measuring the density curve (-> details). Resolution, sharpness and graininess are less easy to describe and determine. The focus here is mostly on subjective impressions and descriptions; there are practically no quantitative statements on this.
The reason for this may be that in pictorial photography, it is ultimately always the subjective impression that is decisive and not abstract figures that are perhaps only of academic interest. Nevertheless, it seemed interesting to me to explore whether subjective experiences and impressions are also reflected in quantitative figures. To this end, I developed a procedure that allows quality parameters of film-developer combinations to be determined and compared.

The method for determining the resolution is based on the microscopic evaluation of the image of a reference structure (Siemens star). This evaluation is carried out completely numerically and analytically, and no subjective evaluation is performed at any point. Together with the resolution, the method provides reference values for the edge sharpness and the susceptibility to bloom (halo) of a film-developer combination. (-> Details).
The determination of the key figures of the grain structure is based on the microscopic evaluation of evenly exposed areas of optical density D=1. This is an extension of the method proposed by KODAK for determining the RMS granularity. (-> Details).