Toe speed of TMAX 400 (was fridge and heat problems)

"Phil Glaser" wrote in message
om...
Donald Qualls wrote in message
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Phil Glaser wrote:

Now here's an interesting thing. I've been developing
TMY in HC-110
diluted 1:63 (unofficial dilution "h") for the
accutance affect. After
several tests, using a densitomter to get the Zone I
exposure to .1
over b+f, I arrived at EI 200. So here I _lost_ a
whole stop. That,
and the noticably more grainy result, are motivating
me to look for a
new combination.

IOW, you got what most Zonies get -- an EI one stop
slower than the ISO
speed. I don't call that a speed loss, I call that a
disparate method
of measuring speed. However...

I'd like to hear from others who measure the toe speed
this way. Could
it be that a different developer would give me the same
toe density at
a higher EI, or is a one-stop speed loss indeed typical
for us
"Zonies"?

First, TMY is not a "slow to medium" film; second, you
may find it
advantageous (especially with HC-110) to reduce
agitation and develop
for contrast rather than toe density. Done your way,
you get a flat
negative with EI 200; developed for mid-tones, you'll
get a normal
negative with EI 400, requiring longer development in
the same dilution.

But doesn't this beg the question? Is the negative still
"normal" at
EI 400 if the Zone I exposure is thin? I have also
exposed some TMAX
at 400 and 320 and found that finer shaddow detail is
lacking.

Also, I don't think my negatives are flat. My zone VIII
density is
around 1.15 and I'm using a condensor enlarger. I'm
finding that I get
a decent print with a # 2 or even 1.5 contrast filter (I
realize that
this is not the same thing as _grade_ 2, but it gives you
an idea --
my negatives are not flat).

This past weekend, I souped 4 rolls of TMY 120 in HC-110
Dilution G --
1:119 from USA syrup -- some for 15 minutes at 70 F with
reduced
agitation (every 3 minutes), some for 15 minutes at 70 F
with normal
agitation (every minute), and some for 12 minutes at 74
F (compensated
for increased temperature) with normal agitation. The
roll with reduced
agitation is clearly of reduced contrast compared to the
others, but all
have similar toe speed -- toe is affected primarily by
total
time/temperature in the soup, regardless of agitation,
because local
exhaustion doesn't affect lightly exposed areas.
Mid-tones, and more so
highlights, get less development with less agitation,
which reduces
contrast (because less agitation gives less fresh
developer in areas
where it exhausts fastest -- and this is most pronounced
at high
dilutions). So, when you reduce agitation, you have to
develop longer
to get the contrast back to normal -- and in the
process, you gain speed
in the toe.

When you say "gain speed in the toe," it sounds like you
are
suggesting that longer development I will regain the toe
desnity I'm
looking for but, with less agitation, retain the proper
highlight
density?

My concern with this approach is GRAIN. My current program
with HC-110
1:63 seems to be rather grainy. It seems to me that
increasing the
development time is only going to make that worse.


The key, though, is not to develop until your toe is at
0.1 over B+F;
rather to develop to normal contrast and let the toe
detemine where Zone
I falls.

But here it sounds like you are saying _not_ to base
development time
on toe desnity. I'm confused. Could you please elaborate?

--PHil

This is the only post in this thread on my server so I've
probably missed something.
However, "toe speed" is a meaningless term. Film speed as
measured by the ISO method has a speed point determined
after development so that a specified _range_ of exposure re
sults in a specified _range_ of densities, in effect a
contrast index is specified. The speed point is where the
density is log 0.1 above fog and base density. Note that the
term "base fog" is incorrect, this comes from a confounding
of the two terms fog and base density. The base density can
be insignificant, as it is for most sheet and roll films, or
it can be considerable as it is for many 35mm films which
have a pigment in the support to reduce light-piping and
give additional anti-halation reduction.
In any case, the point where the silver density is log
0.1 above the total of the fog and the base density is
assumed to be the minimum usable density. The film speed is
calculated from this with a safety factor multiplier of
1.25.
Since the ISO method does not take into account the
contrast or gradient of the toe area the shadow contrast can
be too low for some purposes and with some films when
exposed using the ISO speed. Givinging the film somewhat
more exposure will push the minimum densities of the image
up the toe to a point where the contrast is greater. This
may result in better tonal rendition. This effect is totally
ignored by the Zone System.
Also note that the ISO speed is valid only when the film
is developed using the developer specified along with the
speed rating (it can be any developer) and to the contrast
index required by the standard. When film is developed to a
lower CI, for instance for use in condenser enalarger, it
must be developed less and the speed will be lower than that
give by the ISO test. For most film an adjustment to a one
paper grade lower contrast will require an increase in
exposure of about 3/4 to 1 stop. The difference in printing
contrast between a diffusion enlarger and a common partly
diffuse condenser enlarger is about one paper grade.
The idea of the Zone System is to expose and develop
negatives so that scenes of varying brightness ranges will
be represented by a constant density range on the negative.
This will allow printing of all on a single grade of paper.
However, the eye expects to see contrast approximating the
original scene so the Zone System, used without some
understanding and care, can result in very unnatural looking
tone rendition.


--
---
Richard Knoppow
Los Angeles, CA, USA