From: bjs@uts.amdahl.com (Barry Sherman)
Newsgroups: rec.photo
Subject: Re: t-Max Films
Date: 8 Sep 92 20:35:56 GMT
Followup-To: rec.photo
Organization: Amdahl Corporation, Sunnyvale CA

Paul Salanitri writes:

>Also, what is the best developer to use to get the FINEST grain possible on 
>TMAX-100,  I don't mind exposing at 25 even if I have to.

There's a problem with fine grain developers.  Basically what they do is
to dissolve the little clumps of silver and this reduces sharpness.  I.e.
in most cases finer grain developers lead to a decrease in perceived
sharpness (acutance) and coarser grain developers lead to an increase in
acutance.  According to the literature, there is one exception:

You might take a look at a book about pyrogallol (the standard developer of
Edward Weston).  There's a new formulation that seems to show great promise
developed by Gordon Hutchings in California.  His book, "The Book of Pyro",
is available from Light Works in Sacramento, California, phone number 
1-800-776-9678.  I assume that since the '1' is the U.S. country-code that
you'll be able to employ the '800' toll-free service from Australia.  They
also sell the developer ready-mixed.  This is a nicety as the powder is
quite toxic.  

Anyway, pyro (really pyrogallic acid) has several interesting effects:

* It "tans" (slightly hardens the surface of) the gelatin, reducing movement 
  of the silver clumps during development, thereby increasing acutance.

* More relevant to the question, it produes a yellow-green stain in proportion
  to the amount of silver reduced.  What this means is that you get more
  image density without having to have as much silver present.  This means
  finer grain.  

* It also produces greater "edge effects", which increases perceived
  acutance.

* Finally, it, in common with pyrocatechol, is capable of rendering extreme
  highlights without losing tonal separation.  I.e.  The curve has a very
  long straight portion.  As an aside, I have several 35mm negs that I
  developed with pycatechol (more properly "catechol"), which has some
  similar effects to pyrogallol.  Their image quality is right up there
  with medium format negs.  Most impressive stuff.  

Ok, now having said all that, I must admit that I'm still in the experimental
stages of using this developer.  I've just now figured out a technique 
of development that works with my 4x5 sheet film without producing 
objectionable amounts of uneven development from developer oxidaton.  But the 
results, so far are very promising.  Older Pyro formulations did decrease film 
speed considerably.  But this is a Pyro/Metol super-additive formulation and 
I actually found an increase in film speed, as determined by an exposure which 
gives a Zone 4 (meter reading -4 stops) density of .1 over base + fog:

Tmax 100 (4x5 sheets) in HC110 dil. B:  100
Tmax 100 (4x5 sheets) in PMK Pyro:      125

Tmax 400 (4x5 sheets) in HC110 dil. b:  400
Tmax 400 (4x5 sheets) in PMK Pyro:      500

Just one of, I'm sure, many suggestions,

Barry

-- 


|----------------------------------------------------------------------------|
| Barry Sherman, Amdahl Corp.       | "Any fool can face a crisis - it's     | 
| bjs@ruts.ccc.amdahl.com           |  this day-to-day living that wears you |
|                                   |  out." - Anton Chekhov                 |
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| Amdahl, being a corporation, is a legal fiction.  Therefore it is incapable|
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| said of me as well.                                                        |
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