Effect of negative on Pt/Pd tone

Discussion in 'Alternative Processes' started by Ian Leake, Apr 9, 2007.

  1. Ian Leake

    Ian Leake Subscriber

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    One thing that's always confused me with my Pt/Pd prints is the way the negative seems to change the print tone. I find the area outside the negative consistantly turns a rich middle brown, but the darkest area of the negative (i.e. clearest bits of film) have a much blacker tone with a visibly greater dmax.

    My pet theory is that the film base (HP5+) filters out part of the UV spectrum that Pt/Pd is sensitive to. But has anyone else experienced this? And if so, do you have any better ideas as to why it happens?
     
  2. Vaughn

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    My favorite pet theory is that without the negative base+fog, the borders get over-exposed and actually start to reverse (solarize).

    Vaughn
     
  3. Ian Leake

    Ian Leake Subscriber

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    By jiminy I think you're right. I solarised a print yesterday when I was testing some gampi, and the effect was the same. But I hadn't put two plus two together yet. Sometimes I need someone to tell me the obvious before it becomes obvious to me :wink: Thanks.
     
  4. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    The solarization effect is in part due to overexposure of the print. If your borders outside the film area are starting to solarize, you're overcooking your print. Time to look into adjusting your negative exposure/development regimen.
     
  5. Vaughn

    Vaughn Subscriber

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    LOL! I hope it is "obvious"! I am still waiting to hear from a real expert around here to give us the un-obvious "real" answer!

    But as FC commented, it would be interesting to note how much exposure it takes to solarize the coated paper w/o a negative -- then try to keep one's exposure below that time....especially if one includes the border around the negative when displaying one's prints.

    Vaughn
     
  6. sanking

    sanking Member

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    This is caused by solarization. lt happens when the negative has been develped to a DR that is to high for the specific paper/sensitizer. What happens is that by the time you expose long enough to bring in the highlights the very deepest shadows, and clear area outside of the image area, is over-exposed by 2-3 stops.

    The cure is to develop your negatives to a density range that correponds to the exposure scale of your process. Or adjust the exposure scale of the process to match the negative DR.

    Sandy King
     
  7. Ian Leake

    Ian Leake Subscriber

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    Thanks Sandy. It seems that every time I think I've cracked a bit of the process I discover something that throws everything in the air again :sad: Oh well, at least each time I get a little better at this :smile:
     
  8. Kerik

    Kerik Member

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    If you're printing with pure palladium, adding some platinum to the mix will often reduce or eliminate the reversal effect.
     
  9. Ian Leake

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    I thought it was worth updating this thread to help out anyone who reads it in the future. After some testing I've established to my satisfaction that while the symptom was solarisation, the cause was not over exposure to UV or over developing my film. I was in fact using too little pt/pd solution. Adding a few more drops has solved the problem AND improved the print quality :smile: Thanks for your help everyone.