SLIMT notes for those interested

[Ulophot]

Hi, icracer. I do not have the ability to analyze and create curves. I am reporting on both visual examination of the negs on a lightbox, and on prints made identically from representative negs. See more below. i realize that this may seem to leave lots of wiggle room for error to someone used to that level of precision. If I should be proven wrong about this anomaly, so be it; I have no ego investment in this; I'm just following a surprising effect and trying to understand its cause for practical field use.

Hi, Doremus, and thanks as always for your thoughtful and experienced insights.

I am beginning the suspect the same with regard to an emulsion and/or other-layer difference between the formats. I will process a 120 roll (all frames of a controlled subject, identically exposed at EI 400; half the roll processed with the SLIMT and then added to the other half, the two developed together in the same tank with N development. We'll see what happens.

As I have indicated, the low-value boost came as quite a surprise, and if I had not been able to replicate it, with care against variables at each step, I would naturally have dismissed it. I assumed I had made an error with the 35mm after seeing no effect in the 4x5; I tested both again and got the same results as before. I have no idea why this approximately 1/2-stop or so density increase is occurring at the low-end-- as you say, it appears to make no sense, since the higher values are being slightly depressed. It would be interesting for someone else to perform the same test. (And haven't we heard enough claims over the decades about miraculous speed increases?)
As you know, Kachel notes that negative films tend to require the KBr solution to prevent fog, which I am using. I don't see fog, looking at the film or printing, though this is something I can trying printing for, i.e., making prints that place clear film around Zone V or VI to compare them.


I'm not sure how this will all pan out. I can only tell you that I am seeing the same result repeatedly in 35, which I first ascribed to N+1 with SLIMT compared with N without, shooting the same sort of test. And, there is an apparent grain increase evident in the small format enlargements, as usual with SLIMT treatment.

[Ulophot]

4/18

I have now tested 120 size, and have gotten results similar to those in 35mm, i.e., a boost of roughly ½ stop in the Zone II-III range and a slight decrease of density in the high values. The decrease in the high values appears slightly less to me than in my 35mm tests, but I don’t have identical values to compare. What I noticed in this test, however, was what appeared to be a slight boost up into the upper mid-values as well. However, closer examination showed that in those areas, e.g, out-of-focus background objects through an aluminum-screened window, and the slightly fuzzy surface of a darkish T-shirt, had a “texture” in which tiny “points” of very low value were getting the boost from the SLIMT, thus averaging out the value slightly higher, much as a fine checkerboard pattern of black and white, if seen from a distance sufficient that the eye’s resolving power is challenged, appears solid gray. This middle-value difference is small and perhaps a little more noticeable in the 120 size because of the smoother tonality and less obvious grain; it appears mostly as a decrease in texture, as in the T-shirt surface.

After making prints of two randomly selected frames, one from each half of the roll (see procedure in my original and subsequent post), I chose two other frames, just in case they might show some difference I was not seeing in reviewing the negatives. While this is not a scientifically rigorous application of method, results did remain consistent. I had shot the test under heavy overcast and continued checking light readings throughout the test, as before.

I tested to see if the density increase might be due to overall fogging, which is the only other thing I could think of that would be logical with respect to the way SLIMTs work. My hypothesis then would be that, although I maintain Kachel’s ferricyanide-bromide ratio, the extreme dilution I used for these tests crosses some threshold for the bromide which reduces its anti-fogging capacity. I printed the clear film between frames (relatively wide in my 645 film) and adjacent in-frame toe values, approx. Zones 0-I ½, to values between a high V and low VI, i.e., on the straight-line portion of the paper curve, where any difference would show up best. The normal and SLIMT prints, developed together, are indistinguishable.

So, the mystery remains, for me, as to why this is happening at all. I could add, that my “Grade 2” is a bit higher-contrast than normal; I print with a cold light source and Ilford filters, but without a CC40Y, so my 2 is more like 2 ½, which may mean that the half-stop difference I am getting in the low values would be slightly less in someone else’s prints. However, not much, and it is there and is repeatable in 35mm and 120. It seems increasingly that either the emulsion or other layers in the sheet film versions of HP5 somehow respond differently. However I wish the roles were reversed! Whether I can coax the same behavior from 4x5—which, is, recall, why I started this whole process to begin with—using a different SLIMT concentration, will be my next test. Frankly, I’ll be astonished if it works, but having come this far, I may as well give it a try.

[Ulophot]

I am adding to this thread again in order to, potentially, close it out; others may have comments to add.

Thanks to the suggestions in private of one of our more experienced and always thoughtful members, I have discovered that a variable I had not considered, rather than the SLIMT bleach, has been causing the density increase, and I worry about even mentioning it, lest I trigger one more debate about it’s use. However, in order to clear the air about my attributions of unexplained density increase to SLIMT, I feel properly obliged to do so. Pre-soaking the Normal, non-SLIMT-treated negative in water evens its density with the SLIMT one, other than a slightly denser top end; even my very dilute SLIMT had some effect there. That is, with this film, in my case, pre-soaking apparently just gives the developer a little more time to work.

I will leave my thoughts off here for the reason given above, noting only that I now remember seeing Phil Davis’s report of increased contrast due to presoaking, which he investigated rather thoroughly with various films and varying results years ago.
Thanks to all of you who contributed to my little side trip through the seeming anomaly. The main thing is to keep learning!