U of S | Mailing List Archive | alt-photo-process-l | Re: Gum tonal range (was Miracle size for gum)

Re: Gum tonal range (was Miracle size for gum)

I don't think gum has a nonlinear transfer function; AFAIK, on
contrary, dichromate processes have a pretty linear transfer function
(as long as the dichromate strength isn't at the extremes = not
excessively weak/strong), hence the non-linear tones in the resulting
print. Our negatives are not linear in any sense, therefore, since
dichromate processes are linear (or much linear when compared to the
"literal" processes - if you like), the translation of non-linear
negative densities to print densities are non-linear too. Said that,
it should be noted that dichromate processes are pretty high contrast
in the highlights. So when thinking the transfer function as a single
entity, it's like a having a stepped / double character; almost having
one inclination in the shadows and midtones, another in the
highlights... (Hoping not being too complex/cryptic.)


2009/10/12 etienne garbaux <photographeur@nerdshack.com>:

> ... nonlinear transfer function of gum ...