Pyro and T-Grain Films - Deux
Too bad the first thread died the death that most of us were expecting, but there were still a few points that I was interested in.
Here's the premise that Sandy started the first thread with: (I added slashes which I hope clearifies the data a bit...)
I guess my problem with the evidence as presented above is that while the data shows that the difference between the Vis and Blue values at Step 11 are very close to the same amount (and as Sandy points out the ratio is also close, percentage wise), the values of the Vis or Blue for the two films are quite different - for the first set of films - the FP4+ Vis is 0.92 and the TMax Vis is 0.67. A similar condition exists with the other pair of films - Tri-X Vis is 0.68 and the TMax Vis is 0.94.
The data is from film tests made of FP4+, TMAX-100, TRI-X 320 and TMAX 400. All were developed in Pyrocat-HD 1:1:100. I chose tests from each film that were as close as possible in Dmax at Step One in Visual mode. Readings were made with an X-Rite densitometer in Visual and Blue modes.
FP4+ / Tmax-100
Step, Visual Blue / Visual Blue
1. 2.10 2.45 / 2.04 2.43
11. .92 1.14 / 0.67 .80
21. .10 .10 / 0.06 .07
TRI-X 320 / TMAX-400
Step Visual Blue / Visual Blue
1. 2.10 2.62 / 2.12 2.60
11. .68 .88 / .94 1.13
21. .13 .15 / .07 .13
For each film at each step the difference between Visual and Blue reading is stain density. It should be immediatly obvious that the percentage of stain for any given step of the tests is approxmately identical for all of the films. The obvious conclusion one must reach is that the T-grain films stain just as well as traditional films like FP4+ and Tri-X 320. I hope this information will serve to debunk the nonesene that T-grain films don't benefit from staining developer
This looks to me that the two films have been developed to a different CI or gamma. I would suggest that these comparisions are not well matched. I suspect that if we matched a set of films where the visual density curves were nearly identical it would show that the T-grain films do not have the same level of stain that the non-T grain films have.
My observation with PMK is that when this is done with FP4+ and TMX, the FP4+ has signifcantly more stain. I have not used TMY so I can't make any comments on it in PMK compared with Tri-X.
I disagree with your assesment. If you see the steps 1 and 21 you will see they are very close in values. Without seeing the middle values it is difficult to asses the liniearity of the films, but it seems to me that FP4+ has little "hump" in the middles values. If this is the case then I would think that for those subjects where the separation of the middle and dark values is important, then FP4+ would be a better choice than TMX 100.
If we discount reading errors, I suspect that the reson for the differences in value 11 is that TMX 100 curve has a more linear behavior than FP4`+ which should have a more traditional S curve shouldering faster than TMX but at the same time moving out of the toe area faster than TMX as well.
The choice of TMY and FP4 was excellent, at least for me: in my use, they share long straight lines, and Sandy's test bears this out.
It is difficult to characterize film's response without mention of the associated developer. In my world, with Xtol and Rodinal, FP4 and TMY have well matched curves, and this data is VERY relevent.
"One of the painful things about our time is that those who feel certainty are stupid,
and those with any imagination and understanding are filled with doubt and indecision"
You are absolutely right in that the films were developed to different average contrast. However, bear in mind that the only thing I wanted to demonstrate with the data is that for any given measurment of Visual Density T-grain films show about the same percentage of stain density increase when measured in Blue mode. This happens at both Step 1 and 11 so there is every reason to believe it would happen at any other step. In other words, whichever step you choose to measure the perentage of stain increase measured from Visual to Blue will be approximately equal for the traditional films as compared to the T-Grain films.
Because of the very different nature of the curves of these films it is not possible to match visible densities all the way from Step 1 to 21. The basic curve shape of the different films, long toe, short straigh line section, and long shoulder for the traditional emulsion films, and shoe toe, long straight line and short shoulder of the T-grain films, simply won't permit a match, regardless of what portion of the curve you choose. There are obviously important implications that one must draw from this conclusion for the different way these films reproduce tonal densities on the print, but that is an issue not related to staining potential.
Have you actually measured and compared the stain of FP4+ and TMAX-100 films developed in PMK in Visual and Blue modes, or is your comment based on a visual observation? I have tested PMK with T-grain films enough to know that they develop a significant stain, but don't have sample tests on hand to compare the actual percent increase with that of traditional films.
Last edited by sanking; 11-22-2005 at 03:07 PM. Click to view previous post history.
tanning is a chemical reaction between the oxidation products of the development process and the gelatine. In T-grain films only major difference is the shape of the crystals, the chemisty is the same. There is no reason why t-grain films would tan any differently regular films.
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[QUOTE=Kirk Keyes]Too bad the first thread died the death that most of us were expecting, but there were still a few points that I was interested in.
Yes, there was a lot of potential value lost. I'd love to see a new thread or series of articles on APUG dealing with testing film and paper. Many of us have never been exposed to ideas and methods newer than the Ansel Adams books. So what IS the state of the art in tests that are both appropriate to modern films and papers, and yield useful information? Is it the BTZS books, or are they outdated as well? I think this information could help many of us as we are forced to adapt new materials from different suppliers.
One difference is that some films have thick emulsion that will develop a lot of what is called B+F or general stain. B+F stain is different from proportional stain in that it is is found in equal amounts in all areas of the negative, including the border areas. It is highly undesirable, at least in my opinion, because it offers no enhancement to image quality and increases exposure times.
Originally Posted by avandesande
The post-development treatment in the used developer, which some authorities championed at one time, tends to produce a high percentage of B+F stain.
T-grain films tend to produce very low B+F stain, which is perhaps one of the reasons many people came to believe that these films did not benefit very much from develoment in staining developers.
Last edited by sanking; 11-22-2005 at 08:19 PM. Click to view previous post history.
I coined the term "general stain" on the M&P site years ago. I am embarrassed every time I hear it. Maybe somebody can come up with a better term.
Originally Posted by sanking
I changed the title of this thread.
I apologise, but I just couldn't stand the spelling mistakes in what I sincerely hope will be an interesting and informative thread!
BTW, I have found APX100 to stain rather more than most other films - can anyone corroborate that observation? Can anyone explain it?
-- Ole Tjugen, Luddite Elitist
My guess that 'fog stain' is more prevelant in films with a gelatine that is a lower molecular weight or has less cross-links. Photoengineer probably has a better explanation than me.
Since tabular grains orientation (perpindicular to the lens) is very important, I would bet that a very 'hard' gelatin was used to keep the grains flat. The oxidation stuff from pyro doesn't migrate through the gelatine very easily and it reacts with the gelatine right next to the silver particle.
I am no photo engineer and this is a guess.