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  1. #21
    RalphLambrecht's Avatar
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    Quote Originally Posted by Nicholas Lindan View Post
    This whole thing is getting curiouser and curiouser... It is possible that the storage conditions - as regards exposure to air between exposure and development - may have some bearing.
    Nicholas

    I have taken another look at my test strips, and I think to have found some evidence to say that additional exposure (safelight or otherwise) is not the cause.

    Please take a look at yours. In mine there is no speed shift around the speed-point area (0.6 above b+f) to speak of. Additional exposure would have a more significant impact there than anywhere else, because the curve is very steep at that point. In my test, the speed shift is purely limited to the print highlights, which speaks for a photochemical effect.

    Do you see the same thing in yours?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  2. #22
    Nicholas Lindan's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    I have taken another look at my test strips, and I think to have found some evidence to say that additional exposure (safelight or otherwise) is not the cause.

    Please take a look at yours. In mine there is no speed shift around the speed-point area (0.6 above b+f) to speak of. Additional exposure would have a more significant impact there than anywhere else, because the curve is very steep at that point. In my test, the speed shift is purely limited to the print highlights, which speaks for a photochemical effect.

    Do you see the same thing in yours?
    No, I don't think safelight exposure has anything to do with it. The problem I had some years ago with a Jobo LED safelight was that the safelight wasn't really safe. It passed the standard test: first fogging a bit of paper, and then putting a coin on the paper and exposing it to the safelight for an extended period of time. However, it was fogging the paper, and if the paper had been left there for 15 minutes then maybe the fogging would have been evident soon after the exposure. As it was the fogging was only evident after a few days of latent image maturation.

    I am quite sure there are no gross safelight fogging effects - the margins of the prints and the high density steps show no uniform fogging.

    As you noted, the increase in density is all in the highlights. There seems to be no increase in density in the midetones - but I haven't put the test prints under a densitometer.

    I may be using 'speed' in a way that isn't quite mainstream. In the Darkroom Automation system 'speed' is the amount of exposure needed to get a certain tone on the paper - each tone then has it's own speed, a paper's 'highlight speed' is the exposure required to get a highlight ZVII tone on the paper. The published speed for film is the amount of exposure required to achieve a 0.7 OD density (grossly simplified), in the DA parlance if you wanted 0.3 OD on the film then you would set the meter to the film's 'shadow speed'. The choice of the word 'speed' here is a bit unfortunate - 'sensitivity' would have been better.
    Last edited by Nicholas Lindan; 09-03-2009 at 12:05 PM. Click to view previous post history.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  3. #23
    RalphLambrecht's Avatar
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    Quote Originally Posted by Nicholas Lindan View Post
    No, I don't think safelight exposure has anything to do with it. The problem I had some years ago with a Jobo LED safelight was that the safelight wasn't really safe. It passed the standard test of fogging a bit of paper, putting a coin on the paper and exposing it to the safelight for an extended period of time. However, it was fogging the paper, and if the paper had been left there for 15 minutes then maybe the fogging would have been evident soon after the exposure. As it was the fogging was only evident after a few days of latent image maturation.

    I am quite sure there are no gross safelight fogging effects - the margins of the prints and the high density steps show no uniform fogging.

    As you noted, the increase in density is all in the highlights. There seems to be no increase in density in the midetones - but I haven't put the test prints under a densitometer.

    I may be using 'speed' in a way that isn't quite mainstream. In the Darkroom Automation system 'speed' is the amount of exposure needed to get a certain tone on the paper - each tone then has it's own speed, a paper's 'highlight speed' is the exposure required to get a highlight ZVII tone on the paper. The published speed for film is the amount of exposure required to achieve a 0.7 OD density (grossly simplified), in the DA parlance if you wanted 0.3 OD on the film then you would set the meter to the film's 'shadow speed'. The choice of the word 'speed' here is a bit unfortunate - 'sensitivity' would have been better.

    I know what you mean with speed. The official speed point for paper is 0.6 plus base+fog density, which is unfortunate, because nobody prints that way. Making filters to that speed point makes them less practical than what they could be. I set the speed point to 0.09 absolute reflection density (usually 0.04 plus base+fog), where I see my Zone VIII, which I print for.

    I have a question into Kodak and Ilford retired researchers. They may be able to shed some light (pun intended) on the story.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #24
    clayne's Avatar
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    Quote Originally Posted by jongcelebes View Post
    I mean, I can't say anything but thank you. I get info more than I need (and it's good).
    This forums make people like me (no access to workshop/teacher) to taste darkroom experience. Even it might brutally wrong and unusual.
    I usually develop my sheets on an as-i-go basis. Not more than 5 minutes usually. Never noticed any difference with that time-range, of course. You might consider looking for a darkroom tray kit as well, as you can make use of vertical space at the expense of a little bit more care when transitioning trays.

    Victor, glad to see you are getting into darkroom printing. It's the "other half" of the equation and so much more enjoyable than slaving around a scanner (even if it takes longer at times).

    I hope to be back in JKT in December. I'll probably be bringing some 12x16 prints to Malaysia, but I may bring some prints for Monty. We should all get together. Take him under your darkroom wing. He has some amazing negatives - as do you.
    Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.

    http://www.flickr.com/kediwah

  5. #25
    RalphLambrecht's Avatar
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    Well, I got some info from my retirement contacts, which I like to paraphrase for general consumption:

    The phenomenon is known as latent image progression in papers to the more familiar latent image regression seen with films. It has hardly ever been discussed in the literature but is well known within the industry. The effect is an unwanted side-effect of the rhodium doping used in high contrast paper emulsions. The mechanism is that rhodium functions as selective desensitiser affecting the faster crystals much more than slower crystals, which has the effect of increasing the contrast. The rhodium atoms are electron traps that mop up photoelectrons generated by the exposure, but some photoelectrons escape these traps to form more latent image in the period between exposure and development. The effect is a reduction in contrast and an increase in density.

    hope this helps
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  6. #26
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    Illford's data sheets say that up to 24 hours causes no noticeable change in the final image.

    I have shot paper pinhole negatives and developed them weeks later with no problems. I'm not saying they didn't shift, but FYI.
    f/22 and be there.

  7. #27
    Toffle's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    Only if you say 'please'.

    Of course I will. The book will be ready for the printer in three months.
    Just in time for Christmas.

    Hopefully less of a sticker shock than the $999 (plus shipping) I see over at Amazon. I know that's just couch money for most of you folks, but my lottery numbers just aren't coming up.

    Cheers,
    Tom, on Point Pelee, Canada

    Ansel Adams had the Zone System... I'm working on the points system. First I points it here, and then I points it there...

    http://tom-overton-images.weebly.com


  8. #28
    RalphLambrecht's Avatar
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    Quote Originally Posted by BetterSense View Post
    Illford's data sheets say that up to 24 hours causes no noticeable change in the final image.

    I have shot paper pinhole negatives and developed them weeks later with no problems. I'm not saying they didn't shift, but FYI.
    It is noticeable allright, but you will only see it in a side-by-side comparison. For paper negatives the effect may actually help by increasing he shadow detail.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

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