From: Richard Knoppow on

"Darkroom User" <Darkroom.User.6a42d68(a)photobanter.com>
wrote in message
news:Darkroom.User.6a42d68(a)photobanter.com...
>
> IanG;886420 Wrote:
>>
>> PYROCAT HD GIVES FINER GRAIN, BETTER SHARPNESS AND MORE
>> TONALITY THAN
>> D76, ALTHOUGH ORIGINALLY DESIGNED FOR LF NEGATIVES IT'S
>> ALSO USED FOR
>> 35MM &120 NEGATIVES.
>>
>> In addition the negatives are extremely easy to print
>> from, with
>> excellent highlights and shadow detail.
>>
>> It's also a better developer for making negatives for Alt
>> processes.
>>
>> Ian
> If it gives finer grain as well as better sharpness than
> D76, then it
> must be good.
> Will I actually see these differences with FP4 Plus and
> T-Max 400?
> What dilution and times for the small Paterson-tanks?
>
>
>
>
> --
> Darkroom User
Well, finer grain is open to the question of how that
was determined. Lots of developers yield finer grain than
D-76, some modern ones, notably Xtol, also deliver somewhat
higher speed but most fine grain developers loose some
speed.
Pyrochatichin, which is related to pyrogallic acid but
is a different chemical can be used in developers which have
strong edge/border effects. This gives the illusion of
sharpness. There is another effect of certain developers
containing pyro and its relatives, that is that it tans the
gelatin image wise. The variation of index of refraction
after development can lead to a similar kind of edge effect
which is visualized as "acutance" or the impression of
sharpness. Note that "acutance" is a Kodak term for this
illusion. High acutance films do not, in general, increase
resolution, in fact they may reduce it. However, where one
is working with small negatives acutance effects will
partially compensate for the lack of sharpness in the
lenses. Note also that border/edge effects, and hense
acutance, is of a fixed scale so that its effect is
dependant on the magnification of the image on viewing. It
can have a quite significant effect on 35mm negatives but
will be virtually invisible on a 4x5.
Graininess also gives the illusion of sharpness. A
somewhat blurry image when overlayed with a sharp grain
pattern will appear to be sharp, at least at first.



--
Richard Knoppow
Los Angeles, CA, USA
dickburk(a)ix.netcom.com


From: Lew on
What about film speed? Are there any fine grain, staining developers
mixed with phenodone, for example, to give the speed increase we
experience with xtol?
From: Richard Knoppow on

"Lew" <lew1716(a)gmail.com> wrote in message
news:ec481232-75a4-4eee-93ec-bbec5eeee1de(a)u26g2000yqu.googlegroups.com...
> What about film speed? Are there any fine grain, staining
> developers
> mixed with phenodone, for example, to give the speed
> increase we
> experience with xtol?

I don't know. Imagewise staining is produced by some
phenol type developers as is imagewise tanning. Pyrogallic
acid and Pyrochatichin (there are other spellings) are
formost among the staining developers but hydroquinone can
cause imagewise tanning without the staining. Pyro has been
mixed with other developing agents, particularly Metol, but
that was done beause the two tend to preserve each other and
extend the life of the developer. Curiously much of the
reseach done on Pyro developers before they were pretty much
supplanted by M-H types was to devise non-staining
developers. The reason is that the stain image affects the
printing density in a way that varies with the spectrum of
the printing illumination and with the spectral sensitivity
of the printing material, plus it can be difficult to
measure because the densitometer used must match the
spectral sensitivity of the printing material. All is much
easier when the image is neutral. You can get some idea of
the increase in effective density for blue-sensitive
materials by looking at the negative though a blue filter.
Its also possible to bleach out the silver image which
leaves only the stain image. That is one way of determining
the effectiveness of a developer in forming a stain image.
The effect desired by most workers using current
materials is the self-masking effect of the stain image when
used with variable contrast materials. It tends to lower the
contrast of the highlights flattening out the very high
contrast produced by some modern films. In effect it creates
a shoulder on the film characteristic. Might or might not be
desirable and may not be much of an effect on some material.
Grain is affected by many variables: the activity of
the developer is one, generally less active developers are
less grainy; another factor is the pH of the developer,
higher pH (more alkaline) tends to produce coarser grain;
the presense of halide solvents affects grain somewhat but
not for the reasons popularly supposed. The solvent, sulfite
in most developrs, does not "etch away the grains" but
rather affects the way the crystals grow as they are
developed. Up to a certain point the presense of a solvent
will increase film speed because it makes more development
centers available to the developer. This is one reason that
D-76 has become the reference standard for film speed. When
more solvent is present, or a stronger solvent such as
sodium thiocyanate, is used the film speed goes back down
because the solvent can destroy some of the latent image
centers.
The total range of speed variation from "normal" type
developers is about 3/4 stop more to 3/4 stop less than
D-76. Some Phenidone developers, notably Xtol, T-Max RS,
Microphen, as examples, increase speed about 3/4 stop. Some
very fine grain developers such as Perceptol and Microdol-X
decrease it about 3/4 stop. About the only developers which
loose more speed than this are the old fashioned
paraphenylenediamine super fine gain developers. A pure PPD
developer (with no other agent added) can loose as much as 5
stops! These developers can also produce severe dichroic fog
on modern films and do not, for the most part, produce any
finer grain than Perceptol or Microdol-X
In general, film speed and fine grain are not
compatible. Probably the best compromise is Xtol which
yields slightly finer grain and slightly higher speed than
D-76 along with good sharpness and good tonal rendition.
Whatever reliability problems it had in the past seem to
have been cured.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk(a)ix.netcom.com


From: Thor Lancelot Simon on
In article <Darkroom.User.6a42d68(a)photobanter.com>,
Darkroom User <Darkroom.User.6a42d68(a)photobanter.com> wrote:
>
>IanG;886420 Wrote:
>>
>> PYROCAT HD GIVES FINER GRAIN, BETTER SHARPNESS AND MORE TONALITY THAN
>> D76, ALTHOUGH ORIGINALLY DESIGNED FOR LF NEGATIVES IT'S ALSO USED FOR
>> 35MM &120 NEGATIVES.
>
>If it gives finer grain as well as better sharpness than D76, then it
>must be good.

It also gives world peace and free beer. You can be sure it is excellent.

--
Thor Lancelot Simon tls(a)rek.tjls.com
"All of my opinions are consistent, but I cannot present them all
at once." -Jean-Jacques Rousseau, On The Social Contract
From: David Nebenzahl on
On 8/11/2010 9:52 AM Thor Lancelot Simon spake thus:

> In article <Darkroom.User.6a42d68(a)photobanter.com>,
> Darkroom User <Darkroom.User.6a42d68(a)photobanter.com> wrote:
>>
>> IanG;886420 Wrote:
>>
>>> PYROCAT HD GIVES FINER GRAIN, BETTER SHARPNESS AND MORE TONALITY THAN
>>> D76, ALTHOUGH ORIGINALLY DESIGNED FOR LF NEGATIVES IT'S ALSO USED FOR
>>> 35MM &120 NEGATIVES.
>>
>> If it gives finer grain as well as better sharpness than D76, then
>> it must be good.
>
> It also gives world peace and free beer. You can be sure it is excellent.

My sentiments toward pyro as well. Not worth messing with, unless one is
part of the more-exotic-than-thou brigade.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
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