Response to How to calculate Tetenal's Beta

Beta has nothing to do with Tetenal, but is a standardized expression of the the relation of the amount of light and the "blackening" of the emulsion. The term has been used in sensitometry for a long time. That's how you find it: On a standard graph of the film you determine "point A", 0.1 log. densities above base fog. This determines -- as everyone knows -- the filmspeed. Then you determine "point B" on the graph, which received 30 times the exposure of "point A". You now can draw a triangle and the tanges of angle alpha is refered to as "beta". It tells you how steep the Line AB runs. Most film manufacturers used to state developing times for beta 0.7 and beta 0.55. The first was considered the optimum for diffusor type enlargers, the second the optimum for condensor type enlargers. With a contrast ratio of 1:30 you would get a negative that would print on a "normal" paper grade. 1:30 typically would be a landscape scene without direct sunlight. This was a far superior system then to state a gamma of around 0.6-0.65 which is most commonly done today, which will not give an adequate contrast negative for optimum quality. This all may sound a bit complicated in the description, on the standard graph it will become evident. Tetenal has excellent literature which explains sensitometry.

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