D76 Developer
George Goodloe
so why?
Leonard Evens
> What is the advantage of diluting D76 1:1? Does it give finer grain and if
> so why?
>
Among other things it allows you to develop twice as much film from the
same batch. It also lengthens the developing time. If the developing
temperature is high, in some cases, the developing time at full strength
might be too short for uniform processing.
--
Leonard Evens l...@math.northwestern.edu 847-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
maf
if
> > so why?
>
> Among other things it allows you to develop twice as much film from the
> same batch. It also lengthens the developing time. If the developing
> temperature is high, in some cases, the developing time at full strength
> might be too short for uniform processing.
Diluting a developer with sodium sulfite (D-76, XTOL, etc.) increases
sharpness and increases apparent grain. This is because the amount of sodium
sulfite in straight D-76 softens the grain and reduces the sharpness. Using
a 1:1 dilution (or even 1:2 or 1: 3) is a good compromise between sharpness
and grain.
Straight D-76 is normally re-used, but diluting it means that it should only
be used as a one-shot developer. This improves consistency, which is
important in getting good negatives with proper density and contrast.
Richard Knoppow
"George Goodloe" <goo...@gmx.net> wrote in message
news:01c28020$3fab60a0$ad0e3841@gwg1...
> What is the advantage of diluting D76 1:1? Does it give
finer grain and if
> so why?
>
development time where the undiluted time is too short and
for economy where only small volumes of film are to be
developed.
The difference in grain and acutance between full strength
and 1:1 D-76 are negligible since sulfite still has about
similar solvent and protective action.
D-76 1:1 should be used one-shot although a large enough
volume will develop a second roll of film with some increase
in time.
Full strength D-76 will develop several rolls of film if
the time is increased to compensate for loss of activity and
bromide build-up. Kodak gives directions for this. Full
strength D-76 can also be replenished, the replenished
system having a much larger capacity than just reusing it
with increased time. Replenishing requires some care to
insure stable activity. Again, for small volumes the diluted
developer, used once, insures uniformity.
Many developers change characteristics when diluted.
Microdol-X or Kodak D-25, for instance, are very low
activity developers depending on the solvent action of the
sulfite for extra-fine-grain images. The solvent action also
reduces film speed a little due to destroying some of the
latent image. When diluted to 1:3 the concentration of the
sulfite is reduced more than the time is increased so there
is significantly less solvent action. At 1:3 grain and speed
are about the same as for D-76 but there is a significant
amount if edge effect leading to high acutance (edge
contrast).
Rodinal, on the other hand, does not have much sulfite in
it but is quite active. When diluted the grain is reduced
rather than increased because the dilution lowers the pH,
reducing the amount of grain clumping, and the lowered
activity also changes the morphology of the developing
crystals. The reduced activity also tends to lower film
speed.
So, the effect of dilution depends on several factors
including the amount of sulfite and the rate at which
development time is affected by dilution. This last varies
with the developing agents used and the type of formula.
--
---
Richard Knoppow
Los Angeles, CA, USA
dick...@ix.netcom.com