Hi Michel, I think the very best way to get a full grasp on this huge subject is to understand the different chemicals of developers/properties+curves of emulsions in general. For example, what is characteristic of metol? in what quantities compared to the other chemicals in the soup? What about hydroquinone? What does the shoulder and toe region of an emulsion tell you in advance of an emulsion's tonality and contrast. Etc. A great place to start is The Negative by Ansel Adams. It's The Bible as far as I'm concerned; even if the emulsions/developers themselves are out of date in some cases, yet the theoretical grounding in TN is constant.(posted 8859 days ago)If, however, you have a particular developer/film combo you are interested in talking about, this forum is a great place to start, in conjunction with your own experiments. Sorry if this is a little pedantic or 'hi-falootin'...shawn