[pure-silver] Re: Developer and Neg Density


----- Original Message ----- From: "Adrienne Moumin" <photowonder2010@xxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, June 24, 2006 8:12 AM
Subject: [pure-silver] Re: Developer and Neg Density


Thanks so much, Richard, for all the good info. I know how much time & effort it takes to think about & type it in all that, and I really appreciate it!

However, I am still confused about the comment in your prior post in response to Mark's:

"You can loose nearly one stop by developing in either Kodak Microdol-X or Ilford Perceptol (they are identical). When used full strength these extra-fine-grain developers loose about 3/4 stop when compared to D-76. The results will be normal contrast negatives."

in light of your more recent one in repsonse to my post:

"Standard developers will all deliver the same contrast if the development time is correct. "

I am feeling dumb here, but I think there is something I am not getting, since to me these 2 statements seem contradictory. So I feel it is better to risk exposing my lack of comprehension than continuing to be in the dark.

Also, I am familiar w/the difference in condenser & diffusion light sources, and the use of graded papers where indicated. However, on both the B&H & Ilford sites, I cannot find greater than a grade 3 in Ilford Ilfobrom Galerie FB (I don't know why they added the "Ilfobrom" designation, not that I really care but I am wondering if it is the same Galerie paper of yore).

And the image I really want to print needs at least a 4 if not a grade 5 so I feel stuck as to a solution. Dialing in max contrast of 0Y-170R-10Y is still rather flat so I am stumped as to how to proceed if I cannot get the higher graded papers.

Thanks again, sorry to be so dense!

-Adrienne Moumin

Negative contrast is controlled by the time of development. The longer you develop, the higher the contrast. Film speed is mainly a function of the emulsion but it can be affected so some degree by the developer. For _the same contrast_ extra-fine-grain developers, like Ilford Perceptol, Kodak Microdol-X, Kodak D-25, all lose some film speed, for these three its about -0.75 stop. Some developers yield a slight increase in films speed, examples are Kodak Xtol, T-Max, T-Max RS, and Ilford Microphen, DDX, ID-68, all of which use some form of Phenidone. Not all Phenidone developers yield more speed but these do, again about +0.75 stop. Again, this is for the same contrast.
This is the answer to your first question: when, say, Ilford Perceptol is used to develop a negative to a specified contrast, and a similar negative is developed in, say, D-76, it will be found that for the same density range the Perceptol negative will require somewhat greater exposure. When certain other developers are used, say Xtol, somewhat _less_ exposure will be found to yield the same density range for the same contrast. In other words, identical negatives can be made from all three developers provided the exposure is adjusted a little and the time of development is correct for the degree of contrast desired.
Other than some special purpose developers there are no "low contrast" or "high contrast" developers, only more or less active. I believe a lot of photographers do not understand the relationship between time of development and contrast and think the same time will work for all developers. Certainly, if one developed for the same time in Dektol and in D-76 1:1 there would be a major difference in contrast, but, if the times are adjusted to be appropriate to the developer, the contrast, at least, would be identical.
Now, beside time, the degree of development is affected by the temperature of the developer and the method of agitation. Time/Temperature charts, as the name implies, give corrections for the developing time at various temperatures for the same contrast. The method of agitation is specified for both Kodak and Ilford films.
The usual criteria for the contrast of the negative is one that will print average contrast scenes onto Grade-2 paper.
The contrast of the print can be controlled by varying the paper grade or by adjusting the contrast of the negative so that it will print acceptably on "normal" grade paper. This last is the idea of the Zone System.
Note that film speed is not a fixed value as is easily believed because each box of film carries a speed number. The speed on the box is determined by a fixed standard of exposure and development (and, indirectly, contrast) as specified in the ISO standard. If the development is varied to change the negative contrast the speed will change too. Othewise the shadow densities will become too low.
If you wish to print on a graded paper which is available in only limited grades you must adjust negative contrast to match the paper and printing method. While one can estimate the required negative contrast testing is necessary to be certain.

Because condenser sources of the sort used in most Omega and Besler enlargers are partially diffuse, the Callier effect is not very great. The rule of thumb is that the condenser will be equivalent to about one paper grade more contrasty but my experience is with my D2v is that its less. Since you use a color head you have a diffuse source.
The color head settings for variable contrast paper will not cover the full range of the paper. To get the end values, i.e. minimum or maximum contrast, one must use filters. I've occasionally needed Grade-0 for some bulletproof negatives and have used Grade 5+ very occasionaly for some available light negatives that were so thin its hard to see any image at all on them. The extra-hard paper will bring out an image, not of first quality of course, but something. Of course, the high conrast also brings up all the negative blemishes and any irregularity of illumination in the enlarger. These end grades are mostly for salvage although very good prints can be made using very low contrast paper.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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