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[MF3D.FORUM:953] Re Scala (was First Impressions)


  • From: "Brown, Fritz - LABS" <BrownF@xxxxxxxxxxxxxxxx>
  • Subject: [MF3D.FORUM:953] Re Scala (was First Impressions)
  • Date: Wed, 12 Jul 2000 08:54:55 -0600

Sam writes concerning Scala:
;The first thing I noticed was the flatness and lack of detail in the 
;shadows.

I have to admit that my limited experience in viewing Scala slides tends to
fit with Sam's impression.  I have found them to severely lack contrast.  I
think the problem was a philosophical one during the development of the film
and processing.  It seems from the slides that I have seen that Agfa was
going for a long tonal range scale film similar to what people want in a
black and white negative film.  The problem is that for a tranparency, that
tends to compress the scene contrast into one end of the film or the other.
One ends up with either black and gray slides or gray and white slides,  but
getting a scene to reach both Dmin and Dmax requires an extreme amount of
scene contrast.

A contrast of a good slide film should approximate the contrast of the scene
being photographed.  An "average" scene outdoors has approximatly five stops
of illumination difference between fully illuminated areas and shadow areas.
There are also about three stops of difference in reflectivity of various
objects in an average scene.  That adds up to a total possible range of
about eight stops difference between the deepest shadow detail and the top
highlights.  If a film has, say, a ten stop exposure range between Dmax and
Dmin, then exposing to get the highlights correct,  puts the darkest part of
the shadows at a dark gray instead of a black.  While exposing to put the
shadow density correctly puts the highlights as a light gray.  Getting the
Zone I parts of the scene to hit close to Dmax and the Zone VIII parts of
the scene close to Dmin requires that there be about nine stops spread
between seven zones (essentially an N-2 development).  The average scene
seldom falls into an N-2 situation.

Eric writes:
;I have seen both 35 mm and MF scala in plano and 35 scala in stereo and the
;results where in no way flat (contrast).

I wonder whether the slides you saw were processed straight or whether they
were pushed to increase contrast.  By varying the first developer times and
composition one can alter the contrast of the slide.  Most of the discussion
that I have scene from other shooters regarding Scala is that normal
exposure and development are not optimal.

;Sam further mentions his work with Maco ORT25 for producing slides.

I'm glad to hear that you have been getting good results from your
develoment efforts.  As I mentioned previously, I have been working on
reversal processing protocols for Maco PO100 and ORT25.  Most of my effort
has been on PO100 so far since I already have a good slow fine grain film
worked out (TechPan).  Results so far have been mixed as far as using the
film as a reversal film.  The good points about the film are that it is a
clear base film so one can get the whites to be truely white.  Secondly,  it
is considerably faster than the TechPan that I am used to.  I am getting
speed in the neighborhood of EI 50 to 64 (as opposed to EI 12 for TechPan).
That speed is good enough for potentialy hand holdable shutter speeds for
wandering around with the Realist in the day-pack.  However all is not rosey
on the PO100 slide front.  The first problem with the film is the fact that
it is an orthochromatic film.  The film is only sensitive to blue and green
light with no red light sensitivity.  The problem with that comes into play
when shooting outdoor scenics.  The sky tends to blow out to a featureless
white because of the blue color of the sky.  That tends to detract from the
appearance of any slide that includes the sky.  I havent tried using a
yellow filter yet in an attempt to bring the sky down (red filters would be
worthless on an ortho film),  but I think it simply isnt going to be a very
satisfying film at reproducing skys (a polarizer might be of help too).  The
second problem that I have encountered is a disturbing propensity of the
emulsion to separate from the base during processing.  This occured both in
processing as a negative as well as reversal processing.  Right now I am
willing to attribute this problem to a batch variation since all the film I
received from Cachet was from the same batch,  but it is definitely
something that I will be aware of in the future and watch out for it in case
it is a more fundemental problem with the manufacture of the film. And
lastly,  the final problem I am having with this film is an inability to
completely clear the highlights.  Comparing the cleared film base to the
densities of the maximally exposed film, there is still a slight residual
density that isn't clearing during processing.  That basically means that
there is some residual undeveloped silver in the extreme highlights after
the first developer that isnt cleared by the thiosulfate in the first
developer, but that is fogged and then developed in the second developer.
The residual density isn't much,  and probably wouldn't be objectionabe,
except for the fact that I know it is there and I want to make it go away.
Anyway, that particular problem is one that I can eventually solve by
twiddling with my first developer.  The spectral sensitivity and emulsion
lifting off are out of my hands (although I think I will write to H.O. Mahn
and suggest that maybe they should try putting their panchromatic emulsion
onto their clear base).

Well,  I'll be off for now.  I hope everyone had a good time in Mesa and
that those that didn't go (like myself) managed to have a good time wherever
they were.  

Toodles.

-Fritz M. Brown