I think the term that Richard was referring to is “acutance”, the perception of
image sharpness by the viewer.
My experience is that staining developers greatly improved over all image
acutance. I found that PMK gave me much better definition in darker areas —
tree bark comes to mind.
At the same time, it allowed me to gain more dynamic range in the finished
print. For example, shooting from inside a room with a bright day lite window.
A straight print resulted in a blown out window. However, there was detail in
the window on the negative. I could burn that area in thus increasing the range
in my finished image.
But like everything in photography, there is a trade off. Too much improvement
in local contrast could result in a halo effect between sharp differences in
strong dark to light edges. I’m told that that was the result of silver
migration from dense to less dense intersections.
Regards,
Bill Riley
On Feb 8, 2021, at 3:28 AM, Luis Miguel Castañeda <octabod@xxxxxxxxx> wrote:
First of all: I have no direct experience with pyrocat-HD itself, but had
some with a few catechol-based developers and other staining developers, like
tanol, finol, and Thornton's dixactol.
I guess none of those are in a different ballpark if not very close brothers;
even some claimed to be the same formulation under a different name.
My experience on staining (either catechol or pyro) is :
- Catechol stain is faint.
- Different emulsions colors differently, with several degrees of intensity,
no matter what kind of agitation you use.
- Most stain color seems to be washed out during fixing and washing.
I've found that the advice of using an alkaline sodium thiosulfate-based
fixer (as TF2) without sodium sulfite keeps as much stain as you will get. I
doesn't keep beyond the day, so I do prepare it just before use. I don't know
the chemistry behind that, it's only a empirical observation after following
advice.
- Without carriyng proper testing which needs more equipment and methods
than most of us have, it's almost impossible to tell apart what is stain by
reduction and what is gelatin toning (inside the picture, of course).
As final note, my lab gets water in a wide range of temperatures depending
the season, so I standarized in 24C processing (75F), as it's easier to heat
in winter than cool down during the long summer. It may take its role in
staining, can't tell as I'm using this temperature as standard for a very
long time.
my 2c.
On Sunday, February 07 2021, 23:01:22, Tim Daneliuk wrote:
Tri-X (at least TXT - how many versions of Tri-X have there been?
Many, methinks.) stains most.
Neither APX 100 or FP4+ stain anywhere near as much.
--
Compare the black-and-white photographs of Ansel Adams, Edward Weston and
Irving Penn, with color or digital. It's the difference between art and mere
representation.
--- Yvon Chouinard
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