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

[etienne garbaux <photographeur@nerdshack.com>]

phritz wrote:

> i've been wondering, is this discussion about exclusively about 
> one-layer-gums?  i think it is.
>      *   *   *
> katharine, with your .75 density range, did you mean single layer or 
> finished print?
I'll let Katharine speak for herself, but it seemed clear that she 
was referring to a single layer -- did you look at the link she 
provided?  She clearly said in a previous post that to get smooth 
tones and wide DR, you need to make multi-layer prints.

> the other thing is, that all tonal ranges are a continuum between 
> black and white. there aren't any steps in reality. even in an 
> extremely short tonal scale is every single shade of grey present in 
> it. it's just a matter of a suitable negative to print them.
True, but....  It is all a matter of mapping.  Mapping luminance 
values in the scene to density values in the negative that will 
enable you to further map them to the desired reflection densities in 
the print.  This discussion has focused on the second half of that 
mapping, the transfer characteristic of the printing process -- how 
the various densities in the negative map to reflection densities in 
the final print.

If one is trying to get "every single shade of grey" in the final 
print, there are easier ways and harder ways.  (As a side note, even 
printers who do not intend to use all the shades of grey in any of 
their images are probably well served by learning how to do so, just 
as singers who never intend to pop up and down an octave at a time in 
performance nevertheless are wise to do so when practicing.)  Any 
high-contrast printing process makes getting smooth transitions and 
all shades of grey in the final print difficult.  It's much easier to 
differentiate the tones in the scene clearly when you expose and 
develop the negative (i.e., make long-scale negatives -- as long as 
you don't run out of the film's capacity to render them), then use a 
low-contrast printing process to map the well-differentiated values 
in the negative to the final print values.  (The same applies, 
mutatis mutandis, to digital imaging, as well.)  Asking a printing 
process to amplify gradations -- to dig them out of a negative when 
they are barely there in the first place -- is rowing against the current.

Of course, gum printers come from this the other way round -- faced 
with a process that is inherently quite contrasty and nonlinear, how 
does one get the tonal range one desires?  Multi-layer printing is 
one of the most powerful tools, as I understand it.

Best regards,

etienne