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Thread: RAF Pyro-Metol

  1. #21
    Helen B's Avatar
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    Gerald,

    Yes, I wouldn't expect much of a difference either and consistency is more important than absolute accuracy here. I guess that the quantities of developing agent in the original formulae are probably rounded to the nearest twenty grains (about 1.2 g) or so anyway. I didn't mention the error because I thought that the difference was important, and I didn't think that it was worth mentioning that it wasn't important. I mentioned it because there appears to be an understandable and common lack of awareness of the different liquid measures. It may not have the same potential for catastrophe as the difference in, say, gallons or tons, but I thought that it was still worth knowing. However, if you are going to convert a formula and give the result to three or four significant figures you may as well do it correctly or, maybe better, round it to the same precision as the original formula.

    Best,
    Helen
    PS One thing that did interest me was that for non-staining use the developing agents are a little more dilute, A being diluted 1+2 instead of 1+1.

  2. #22
    David A. Goldfarb's Avatar
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    Quote Originally Posted by Helen B
    PS One thing that did interest me was that for non-staining use the developing agents are a little more dilute, A being diluted 1+2 instead of 1+1.
    I'm a little confused. I thought that in your source, the non-staining version was used 1+1+1 (A+B+C). Does it recommend that it then be further diluted, as in 1+1+1+6 (A+B+C+H20)? In Haist, the staining version isn't diluted at all--just straight 1 part A and 1 part B.

    I checked Haist (which was my source), by the way, and indeed, his source is Erith, and I suspect Chapman's source is Haist, unless he also got it from Erith and just made the same error.
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  3. #23
    Helen B's Avatar
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    "A being diluted 1+2 instead of 1+1"

    Sorry for the confusion - I was just simplifying 1A+1B+1C as 1+2 and 1A + 1B as 1+1 to emphasise the comparative dilution of the developing agents in A.

    Best,
    Helen

  4. #24

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    Helen,

    My post was not intended as any sort of a criticism but rather to make the point that photography is a forgiving medium.

    I do appreciate the information about the difference in fluid ounce measurements and have corrected my copy of the formula.

    Jerry

  5. #25
    David A. Goldfarb's Avatar
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    Quote Originally Posted by Helen B
    "A being diluted 1+2 instead of 1+1"

    Sorry for the confusion - I was just simplifying 1A+1B+1C as 1+2 and 1A + 1B as 1+1 to emphasise the comparative dilution of the developing agents in A.
    Thanks. That makes more sense now.
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  6. #26
    craigclu's Avatar
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    Has anyone been pursuing any further testing on this? I was feeling like I was winding down on some decisions about specific developer/film combos to settle into and then thought it might be worth investigating a speed enhancing, tanning developer like this, especially on a medium speed film such as FP4+. I'm getting real world speeds of 160-200 with HP5+ with the developers that I like best and thought it might be worth the time to also look into FP4+ at 200 if the overall look is something that I like. I'll be trying it, now that I'm curious, but would like to know what others have discovered along this line?
    Craig Schroeder

  7. #27
    David A. Goldfarb's Avatar
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    I'm still testing, but I don't typically shoot HP5+ or FP4+. If you go to the Chemical Recipies link, then "Staining Developers," I've been posting results as I get them over there, and would welcome results of anyone else's tests. Here's a direct link--

    http://www.apug.org/forums/article.php?a=143

    I think HP5+ would be a good candidate for RAF P-M.
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  8. #28
    David A. Goldfarb's Avatar
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    Ran another more real-world test roll of old TX 400 under various lighting conditions. EI3200 seemed right on for daylight, but about a stop under for indoors in tungsten.

    I shot some indoor portraits recently with old TXT (320) 8x10" rated at 800 for safety's sake, and the negs look great. I probably could have gotten away with 1000, but it wouldn't have mattered much. This was under tungsten gallery spots.
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  9. #29
    craigclu's Avatar
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    Sorry to be so lazy but has anyone got the 1L formula recalculated with the Brit based origins adjusted for?
    Craig Schroeder

  10. #30
    David A. Goldfarb's Avatar
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    I'm all tested with the "wrong" formula, so for now I'm sticking to it. It wouldn't be that hard to recalculate.
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