Reciprocity, raw stock keeping and latent image keeping are all controlled by a family of preservatives including heavy metal complexes and organic chemicals. Each company has a proprietary mix of these. Kodak uses Osmium and Iridium in emulsions at levels of a few milligrams / mole of silver. That is a very tiny amount. They also use phenyl mercapto tetrazole and tetra aza indene. There is some information in the various textbooks on this.
Method of preparation of the raw metal salt and the addition method are both critical in getting them to work.
PE
Why can't Ilford, Kodak or Foma match Fujifilm Acros 100 reciprocity?
It would be interesting to know what exactly defines reciprocity and what did Fuji do as to have the best across their range (Fujichromes are outstanding as well), which I guess of course is a very complex parameter given film engineering.
I always like to refer to PE's knowledge, from an old thread discussing Acros:
On a more speculative note, Acros II has this "Made in UK" which may or may not point to Harman; but it is also unknown to what extent do/if they manufacture the film. Might just be finishing-confectioning, coating also, or also everything from emulsion? No one knows.
It would be interesting to ask HarmanBut if they are manufacturing the film from emulsion to finished rolls then they may very well have the capability.
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