Response to tmax developer

I believe the "1 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidinone" compound listed in the ingredients above is what The Film Developing Cookbook says most chemists consider the preferred form of Phenidione today. It is highly superadditive with hydroquione which accounts for an increase in film speed of between one-half and two-thirds of a stop.

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