Die Grenzempfindlichkeit bildaufzeichnender Systeme

Abstract

The image-recording system par excellence for photography by means of a camera is to this day the silver-halide emulsion, in view of its sensitivity, its convenience in use, and its keeping properties. Its performance is, however, far below that of the ideal receiver which would record every individual quantum hit by a localized change in the optical properties of the receiver. The reasons for this situation and behind recent improvements are reviewed under the headings: The Elementary Photographic Process; The Detective Quantum Efficiency; Modern Manufacturing Methods.
The main reason for the relatively poor performance of photographic emulsions lies in the recording and coding of the image by means of a random distribution of go–no go receivers: the emulsion micro-crystals. Systems with regularly arranged lightsensitive cells such as the “charge-coupled devices” (CCD) offer the possibility of much better performance, if a method could be found of immediately transforming the charge image into a picture on, say, a paper base. Nothing of this sort is in sight. Meanwhile photographic films have continued being improved. No striking advances have been made in the sensitivity of the individual micro-crystals in recent years, but by modern coating methods many layers of different emulsions can be applied to a base in one pass trough a machine, and this enables the microcrystals to be packed more closely. Thus light is absorbed more efficiently and spreads less widely in the film. In this way the performance of films as determined by their sensitivity for a given resolving power has more than doubled during the last 15 years, and the cost of photography has been reduced to one quarter in real terms.
Some improvement may be expected from better dye sensitization and more sophisticated methods of development, but on the whole the potential of conventional photographic methods appears to be exhausted.