IC, I value your posts very much, and I have always learned something from you, thank you. I have done what you have just suggested, but I am afraid I cannot see what you have seen. I have a few test strips, on MGWT FB, in front of me. All exposed using different grades. Each has a fairly full range, from paper base white, to DMax. All the strips that have been "blasted" beyond maximum black read the same on my reflection densitometer, and, unfortunately, I cannot distinguish their boundaries even under a strong light. What I am saying is that my reflection densitometer seems to indicate a DMax value at the very level at which my eye cannot do better.
Originally Posted by ic-racer
I am aware that we perceive reflected shadows and highlights in a relative way, depending on the surrounding environment and illumination, very much. This would be the same, I feel, to how I would see shadows and highlights in a transmission scenario, when looking at a negative, in various environments and illumination. However, in both cases, I find that the densitometer, in reflection or transmission mode, seems to agree with what my eye sees, given enough illumination or more.
I am sure I must be missing a point you were trying to make, or perhaps I am not seeing the effect you have described. Many thanks for your suggestions.
That was part of my point above. In many cases, where a reflection densitometer will show the same Dmax, transmission results might vary.
In these cases, you may see changes in contrast or shoulder density of the varying reflection samples.
Again, it is just an interesting 'example' but did you hold them up to the light, so light shines through the paper?
Originally Posted by Rafal Lukawiecki
Also, just to further emphasize that reflection densitometry results from photographic papers can be influenced by many variables, here is a quote from Proposed American Standard Method of Processing for Sensitometry of Photographic Paper—Z38.2.3*
Nothing wrong with using reflection densitometry and there is usually no difficulty with mid zones and slopes (as PE pointed out) but if you are using reflection densitometry in your darkroom to include a reliable D-max in the curves, you need to make sure you account for all the variables to get useful results.
4. MEASUREMENT IN DENSITY
The sample should be illuminated at an angle of 45 degrees to the surface and the density
measured normal to the surface. Samples having a pronounced surface characteristic should have the densities read first in one position perpendicular to the viewing axis. Then the specimen should be rotated through an angle of 90. degrees about the viewing axis and the density measured again. The two values thus obtained should be averaged and recorded as the density for that measurement.
I don't know how many people are familiar with Todd and Zakia's book "Photograpic Sensitometry" but when I was in graduate school it was my 'bible' for photographic technique.
Anyway I would like to quote from the book a passage that further emphasizes my technique of visual estimation of paper response, rather than reflection sensitometry of paper.
Information about log E paper ranges needs to be reliable
. Such information is best obtained by a test in the actual printing conditions, rather than relying on manufacturer's data which are only representative of a product. This information can be obtained by printing a negative step tablet in a standardized way with a controlled light source and at a know magnification if a enlarger is being used. A visual examination
of the print of the step tablet is usually sufficient to establish of the range of log E over which the paper responds."
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So, not to dissuade anyone from employing reflection densitometry, I wanted to point out that in my darkroom it has no role in matching paper to negative.
With that I want to conclude the test of the ESECO sensitometers and now I'll package up Jeff's unit and send it to him. Thanks Jeff for the opportunity to do these tests.
Thanks. I just run simple film tests - no BTZS measurements. A friend used to lend me a Heiland desitometer, but it has, unfortunately, disappeared.
Originally Posted by ic-racer
I would use the reflection densitometer of my TR524 to graph paper and developer tests... if I felt it was necessary. I've told the story several times how I short-circuited my need to do the paper tests because I found two edge-case negatives...
But it's not a bad idea to graph your paper so you know what you are getting.
Next plan... to check for optimum toning times...
What do you mean by "optimum" toning? Simply DMax with selenium? Because toners are also used for, well, "tone", actually meaning hue in this case. And when used more than one at a time, both the perceived and measured DMax are affected. So guess you'll have to narrow your parameters to a specific paper and developer (and specific dev time, temp, and concentration) if you want specific results. Even the color mix on VC papers is a factor.
Yes, exactly. Toning for DMax with Selenium on Galerie.
Originally Posted by DREW WILEY
I understand this might not necessarily be toning for the longest archival benefit, as the DMax may come at a point when not all Silver has been converted to Silver Selenide. But that's what I was thinking of doing.