I don't think that ddx is "primarily a speed enhancing developer"... the msds says it contains 30 - 60% potassium sulfite, which seems to have similar properties to sodium sulfite, with which i am more familiar... such a large amount of reducer would indicate that the chief aim of ddx is reduced grain, which would be necessary with fast (or pushed) films...(posted 8143 days ago)as for resources, get a copy of henry hornstein's _beyond_basic_photography_ ... he gives you all the chemical info you could want, and then compare what you get from that to any MSDS, and you get a pretty good idea of how a chemical works