personal film speed with tri-x and pyro w/ no color densitometer

[craig_allen5]

I'm about to run my first film test using Tri-x and pyro developer. I understand that I need a color densitometer to read the pyro stained neg. How can I read/measure the test negs to detrmine zone 1 density w/o a densitometer?

 

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Help with all phases of the testing procedure will be greatly appreciated...Thanks!

[pete_andrews]

Only the density to blue-green light is important for B&W printing.

You don't need a colour densitometer.<br>A normal densitometer can be

used with, say, a 50 cyan filter under it, or you can do a visual

comparison with a known density wedge, again viewing through a cyan

filter.

[joseph_wasko]

Hi Craig:

 

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Maybe I'm off base here, but it is my understanding that you have

to test all the way through the print phase in order to establish a

personal EI for a film/developer combo. There are additional variables

intoduced in the printing of a negative. (enlarger bulb, paper, paper

developer, lens contrast, etc.) A densitometer will quantify Zone I,

but it won't really tell you how it looks in the final output (print).

 

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Steve Simmons "Using the View Camera: A Creative Guide....."

outlines the procedure in detail. You need a B&W darkroom. I guess if

you don't have a darkroom, a densitometer reading is the next best

substitute. I never went through this elaborate testing. Using the

mfrs. EI and recommended time/temp in processing has almost always

yielded an acceptable image. Good luck with your efforts. You should

get great results because of your dilligence.

[michael_j._kravit]

In his "Te Book of Pyro" Gordon Hutchins provides a section on EI

tests. I have found these to be excellent starting points for the

establishment of a personal EI, but as others have said you must test

to determine the normal processing time to print in your enlarger, in

your darkroom, with your developer on your paper.

 

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Good luck.

 

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Mike

[mark_demulder]

For my particular set of equipment and processes, when I use Tri-x and

pyro, I found that I needed to cut the time recommended in the

Hutchings book by about 25%. Try it and see.

[alan_shapiro]

I am not sure that Pete Andrews is correct in saying that a black and

white densitometer can be used to read pyro negatives if a cyan filter

is used. Hutchings says: "Densitometers designed for black and white

materials usually do not respond accurately to the greenish negative

color even if an auxiliary blue filter is added." Of course Hutchings

isn't Ansel and is therefore fallible :). But of course one would need

a color densitometer to determine if the result is the same.

 

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Just comparing pyro negatives with regular negatives of known density

is probably not too accurate because of the color difference and the

ease with which the eye can be tricked in such a situation.

 

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You might try the following. Get a calibrated step wedge from Stouffer

- about $15.00 if I recall. Then contact print the step wedge

alongside the pyro test negatives. The exposure is not critical. You

then seek the pyro contact which most matches the .1 density step on

the step wedge contact print.

 

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I haven't tried it because I have a color densitometer!

[pete_andrews]

Depends on the design of the densitometer. If it's a visual comparison

type, there should be no problem. If it's an older selenium cell or PM

type, again there should be no problem.<br>The big bugbear is

Infrared. Many cheaper modern instruments don't filter Infrared

efficiently, and use a sensor which has extended red sensitivity.<br>A

fairly simple test for this problem is to put a piece of

heat-absorbing glass from a slide projector under the densitometer.

This glass has a light cyan tint, usually with a density that should

measure around 0.25 to 0.3. If the reading is much higher, then your

densitometer has an Infrared problem. Such an instrument won't even

read neutral density gels correctly either, and you shouldn't use it

for reading Pyro negs or chromogenic B&W film.<br>In fact, I'd go so

far as to say you shouldn't use it, full stop.

[pete_andrews]

Sorry, another afterthought. The step wedge printing method outlined

above has a flaw. You're looking for a certain density in the negative

above base+fog, not an absolute density value.<br>Your negative almost

certainly won't have the same Dmin as the step wedge, and this will

make a comparison between the absolute density of the wedge, and the

relative density of the negative pretty difficult. The way round this

is to sandwich the density tablet with the base+fog region of the

negative to print it. Using a hard paper grade will make the

comparison easier.