Re: physiology vs. sensitometry
Beakman (beakman@netcom.com)
Fri, 7 Jun 1996 14:32:15 -0700 (PDT)
> However, if we are printing on a silver-based paper we know that the
> paper can handle maybe 5 stops at best. Therefore, we either process our
> film to increase contrast, or we use a high-contrast paper. Either way,
> what we have done is "squash" the ten stops of information into the 5
> stop range of the paper.
> >>
>
> This is just not true. You can print anything that you have recorded on a
> negative onto ordinary photo paper. This is hardly surpising as you are
> using the same process - both are silver gelatine. We may often choose not
> to but that is quite different.
>
> However, when you use the term 'stops' about the negative, what do you mean?
> A range of 5 stops in the subject brightness can correspond to a range of
> negative density of 0.2 or 2.0 (etc) in a negative depedning on the contrast
> to which you develop it.
I knew I shouldn't try to write anything when my head was fuzzy! :)
What I meant to say was that printing platinum allows you to use a negative
with a density range that is at least twice that required for a silver
print. Therefore, in recording a scene on film, the negative exposed and
processed for a silver print will have to have more tonal compression
than one made for printing on platinum. And, once you've compressed the
scene, you can never get back that lost tonal seperation no matter what
the density range of your paper is. So it doesn't matter that the silver
paper is capable of a higher Dmax, because you've already lost the tonal
seperation in the neg.
By the way, what I carelessly reffered to as "stops" was supposed to be
"film density steps = 0.3" Sorry for the confusion.
David