From: jay@metran.UUCP (Jay Ts)
Newsgroups: rec.photo
Subject: Re: B&W film reversal processing
Date: 16 Apr 92 22:11:24 GMT
Organization: Metran Technology, Tampa, Florida

rspeirs@javelin.sim.es.com (Ron Speirs) writes:
: The First Developer is an ordinary high contrast negative developer with
: a silver solvent (sodium thiocyanate or sodium thiosulfate) added to remove
: just enough silver to produce clear highlights.  The film is then rinsed.
: The Bleach (potassium dichromate with sulfuric acid or sodium bisulfate)
: removes the *developed* negative image from the film, but leaves the
: *undeveloped* silver halides intact.  The film is rinsed again and goes
: to a Clearing Bath (sodium sulfite) which neutralizes any remaining bleach.
: Then the film is either exposed to light or fogged chemically, which
: makes the remaining undeveloped silver halides developable.  A Second
: Developer, essentially the same as the first developer without the
: halide solvent, develops the remaining "positive" image.

With the Kodak chemistry, there is no separate light exposure of chemical
step; apparently, it is done during the second developer as with the Kodak
E-6 Hobby Pac.

: >	1)  Reversal processing of Tech Pan for pictorial photograpy.  I want
: >	    to see how sharp 35mm slides can be.  The Kodak Kit has directions
: >	    for use with Tech Pan and high-contrast (copy) work.  Is it
: >	    possible to substitute Technidol for the kit's first developer
: >	    to achieve normal contrast (contrast index of ~0.6)?
: 
: This would certainly be worth a try.  You would need to add some Sodium
: Thiocyanate (~2 g/L) as a silver solvent to produce clear highlights.

OK, so I can try that along with the Technidol concentrate packets I just
bought.  But what about development times?  This is something I am very
confused about.  After the 1st developer, is the silver image the same
density and contrast index as would be desired for a good B&W negative?

Above, you say the 1st developer is an "ordinary, high-contrast" one.
What do you mean by that?  (High contrast like D-76 or Kodalith? :-)

: The following is a formula for pictorial Tech Pan processing from about 1979:
: [...] 
: This is for the First Developer.  The remainder of the step in the kit
: should be OK.  Be sure to test and bracket widely to find the E.I.

Thanks (!), but again, I still am missing development times...

: ... Kodachrome also has a coating on the
: BACK of the film like is found on color negative motion picture films.  In
: commercial Kodachrome processing, this layer (colloidal carbon black) is
: removed prior to development.  You wouldn't be able to do this, and so the
: particles from this backing would contaminate your solutions.  If, after you
: have used your processing kit to exhaustion, you want to try this experiment,

I suspected as much.

: >	3)  B&W reversal processing of E-6 films.  Well, why not -- C-41
: >	    films too!
: 
: I think this is like spending dimes to get nickels.  E-6 films can be
: reversed to get a positive B&W image, but remember that there isn't as much
: silver in color films (since it is only a "catalyst" to get the dyes to
: form) as there is in B&W films (where silver IS the image).

Hmm, this still sounds interesting to me.  Perhaps this would work out ok if
there were no thiocyanate in the 1st developer???

: Since E-6
: films are so much more expensive, why?

Actually, I wasn't going to tell anyone, but since you asked, what I had
in mind was Ektachrome Infrared.  It's different from Kodak's (B&W) High
Speed Infrared, so it got me thinking...

: With C-41 colorneg films, the orange
: masking might get in the way.  However, I don't know if the orange masking
: is built into the film or if it is created during development.  I'll have
: to experiment.

If something really interesting turns up, it would still be possible to dupe
it onto T-max 100.

: The person at Kodak said that T-Max 400
: could be developed in the T-Max reversal kit, but NOT T-Max 3200.

I had suspected as much -- The Photographer's Formulary lists a B&W reversal
chemistry which they say works on T-max 100 and 400.  I wonder why 3200 isn't
compatible?

- Jay Ts
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