Quote Originally Posted by Ian Grant View Post
..... So as you can see EFKE recommended 100 ASA (EI) in FR24 developer with KB/R14 (now called KB/R25), however FR24 was a speed enhancing developer like ID68/Microphen, and the lower speed 40 ASA (EI) was in FR5 a fine grain developer which gave a drop in film speed compared to ID-11/D76 .......
Quote Originally Posted by Ian Grant View Post
..... Drew, I mainly used TMax100 before I switched to Pyrocat HD, and with some films I've found a staining developer gives me a slightly higher effective speed compared to Xtol, so I'm shooting Delta 100 & 400, also HP5 at box speed ......
Hi Ian,
If this isn't too much off topic, I would like to ask something about developing.
You speak of "speed enhancing developer" and "drop in film speed". This is a concept that I’m starting to grasp, but not yet fully understand the WHY of it (and that bugs me).
I can understand that any developer works differently and gives different results. So – to get (almost) even results i(n density and contrast )with the same type of film – one must adapt developing times accordingly the use of the type of developer.
But how does a developer enhance or drop a film speed? Is this a way of saying that – instead of increasing developing times – we overexpose the film to compensate the enhancing effect? I suspect there is more to it than that.

Somehow I have a feeling it has to do with the effective ISO (EI) of the film, the type of developer used and also the adagio: “Expose for the shadows, develop for the highlights”. I think it has probably to do with the chemical proces of converting silver during developing: higher speed in the first seconds (called: toe?), then a steady development for some time and then a suddenly drop in speed at the end.
But I can’t put my finger on it yet and that’s bothering me. I want to understand the concepts and thus test & improve my developing qualities (i.e. eliminating more variables like chance) into a standard process.
Like I really grasp the WHY of the concept of “Expose for the shadows, develop for the highlights” since a few months, so now I can explain it and use it in my upcomming tests with Ilford PF4+ in 4 different developers.

I’m a self-educated developer since 2001, but never learned the technical backgrounds (curves, chemistry).
So could you please tell me what you mean with speed enhancing or drop in speed?

(And yes: I should probably dig out and reread my copy of Ansel Adams book “the Negative”, but that is still in storage for now…)

Thanks,
Bert