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  1. #161
    markbarendt's Avatar
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    I can definitely see where measuring contrast could be problematic.

    Quote Originally Posted by Ian Grant View Post
    I'm not familiar with a PML2 but you may need to read more than one colour channel, and its not staright forward.

    One reason this is a murkey area is the stain can act a a contrast filter, or even like a very mild safelight filter.

    When a negative is intensified in a Uranium intensifier it goes redder and is visually less dense but prints with significantly more contrast and as far as a blue sensitive papers concerned needs more exposure.

    Some staining developers give a yellowish stain others redish and this can vary depending on the film as well.

    I use staining developers for prints occasionally and once the stain is formed the choice of stop bath and fixer has no effect on the stain.

    The staining is the same after an alkali fixer or conventional Rapid fixer (unhardened) and is not affected by HCA (sodium sulphite) either.

    Ian
    Mark Barendt, Beaverton, OR

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  2. #162

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    Quote Originally Posted by markbarendt View Post
    So, a color meter like a PML2 could read that right?
    It certainly can. Use the magenta/green and yellow/blue channel.

    The other problem with trying to make predictions based in densitometer readings is that not only does the stain have differing absorbance in blue and green, but VC papers have varying sensitivities in to blue and green light.

    Many years ago, I did some looking into the stain and I took some film developed in PMK and PyroCat HD and I bleached out the silver and then measured the absorbance of these films with a scanning spectrophotmeter. Here's a pdf I made that shows the difference between the stain of these two developers.

    http://www.keyesphoto.com/Resource/T...rocat_scan.pdf

    It believe this data that PyroCat HD gives more UV absorbance/density than PMK, which is useful with alt processes. And is shows that PMK is going to have a greater compensating effect with PC papers than PyroCat HD.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  3. #163

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    This is consistent with what I've seen, and Sandy King's tests/writings. It makes sense. His Catechol developer stains brownish while most Pyro developers range from brown-green to green-yellow, yellow and even yellow-orange. There is more compensation on VC papers with green/yellow stain.

  4. #164
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    great thread. and very informative for someone like me who knew nothing about pyro developers.

  5. #165

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    I missed this thread when it was originally started and I just finished wading through the lengthy postings. But some things generated questions in my mind.

    1. It was said that a pyro negative would have a greater effect on VC paper. It was also stated that a pyro negative would be printed on a Grade #2 or VC #3 papers. Isn’t this backwards? If it has a greater effect on VC paper, then wouldn’t the VC paper be exposed at a lower contrast setting than a single-grade paper? If my question has no basis, then the comments relate to a local-contrast effect and not overall-contrast.

    2. I couldn’t find it but I believe one of the commenters stated in another thread that he was having trouble getting sufficiently dark skies when using pyro developers even when using a red filter. Because of this situation, he was giving up on the pyro and going back to a more conventional developer. Has this position changed? I have also seen this effect and I will keep Xtol for shots involving a heavily filtered sky.

    3. If one wanted to reprint some older pyro negatives using unsharp masking, would there be any issues that would present problems? I could see some with the stain color on panchromatic masking film. Unfortunately, I haven’t done this so can’t provide any input.

  6. #166

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    I learned a lot about pyro from this thread. If I were new to analog photography and read the post I would be tempted to believe pyro is the magic brew. I recommend the reader pick up The Film Developing Cookbook. There is much information not mentioned here about tanning developers. The authors write about low speed, high fog, poor grain, toxicity and unstable working solutions. This seems a developer suited to large format, rotary processing, and images featuring separation of high values. A class of developers for someone who knows specifically what they are trying to achieve and the limitations of other formulas.

    When I look at web sites with portfolios featuring stained negatives, I often see images of moving water, surf, or fog. Some images look like the definition is unnatural. I'm on thin ground discussing pyro images. Never used the developer or viewed "in hand" an actual print. But I have a sense stained negatives favor certain images and may not be suitable as a general purpose (GP) developer.

    Said another way, if you want something that looks different than the look of D-76, tanning developers may be one of several choices.

    XTOL is the front line GP developer. Especially when you consider its sharpness at 1:3 and low toxicity. The speed gain is at least 1/3 gain. The shelf life is 8 months or a few months longer if properly stored. It can be used stock up to 1:3. XTOL 1:3 is arguably as sharp as Rodinal without edge effects. It's a great developer.
    Last edited by Richard Jepsen; 04-08-2013 at 08:56 PM. Click to view previous post history.

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