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  1. #11
    jd callow's Avatar
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    The OP doesn't tell us what the changes are. In my experience I 've had to add Y as exposure time increased. If you are lossing density you add time prior to changing the th efilter pack.

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  2. #12

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    I was hoping someone new of some physics that could explain this observation. As my sales for prints are increasing I need to start chararcterizing changes in paper batches, colorhead height changes, and changes to YMC with respect to exposure to help my efficiencies in the darkroom. My goal is achieve a perfect match in print density and color balance to my master print in three or less 8x10 test prints.

    I must also note that my changes in colorhead height can be very large ranging form 8x10 to 30x40 or from 4x10 to 20x50. Small changes in colorhead height have very little effect on the color temperature of the light source.

    I hope to be doing this in late fall of this year and publish my findings in hopes that others can benefit or note better ways of addressing these issues.

  3. #13
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    I don't think the height is relevant but exposure time is. If you raise the height without opening the lens, exposure time increases which can result in color shifts. This happens routinely with Ilfochrome and there was once a good article about it in PhotoTechiques magazine.

    I am not sure what you mean by adjusting to get a color temp of 5500. What sort of meter are you using?
    Jerold Harter MD

  4. #14

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    A gossen color-pro 3F color meter. I think I paid around $1100 for it several years back.

    I do change the aperture to keep the exposure times between 5 to 15 seconds so that I do not burn out the eight lamps in my colorhead prematurely.
    Last edited by stevewillard; 06-05-2008 at 10:40 PM. Click to view previous post history.

  5. #15
    jd callow's Avatar
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    Quote Originally Posted by stevewillard View Post
    I was hoping someone new of some physics that could explain this observation. As my sales for prints are increasing I need to start chararcterizing changes in paper batches, colorhead height changes, and changes to YMC with respect to exposure to help my efficiencies in the darkroom. My goal is achieve a perfect match in print density and color balance to my master print in three or less 8x10 test prints.

    I must also note that my changes in colorhead height can be very large ranging form 8x10 to 30x40 or from 4x10 to 20x50. Small changes in colorhead height have very little effect on the color temperature of the light source.

    I hope to be doing this in late fall of this year and publish my findings in hopes that others can benefit or note better ways of addressing these issues.

    I'd think no more than 2 or 3 test strips ripped from one 8x10 sheet would be need to match an 8x10 to a 30x40 of the same neg on the same paper. The time can be done by math using Inverse Square Rule -- confirm with your first test strip -- and the colour pack changes can be charted in advance (run a series of tests at 8x10 up through 30x40 and note the deviation) -- tested on the first test strip (remembering that light output is altered as filter density changes) -- or refigured with the second test strip.

    Then all you need to do is put your paper down and print a full one to see how much crap you forgot to clean off the neg.
    Last edited by jd callow; 06-05-2008 at 11:25 PM. Click to view previous post history.

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  6. #16

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    Quote Originally Posted by jd callow View Post
    I'd think no more than 2 or 3 test strips ripped from one 8x10 sheet would be need to match an 8x10 to a 30x40 of the same neg on the same paper. The time can be done by math using Inverse Square Rule -- confirm with your first test strip -- and the colour pack changes can be charted in advance (run a series of tests at 8x10 up through 30x40 and note the deviation) -- tested on the first test strip (remembering that light output is altered as filter density changes) -- or refigured with the second test strip.

    Then all you need to do is put your paper down and print a full one to see how much crap you forgot to clean off the neg.
    Thanks JD. That is a great starting point.

  7. #17

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    Quote Originally Posted by stevewillard View Post
    A gossen color-pro 3F color meter. I think I paid around $1100 for it several years back.

    I do change the aperture to keep the exposure times between 5 to 15 seconds so that I do not burn out the eight lamps in my colorhead prematurely.
    Longer times won't [or at least shouldn't] hurt your bulbs any. The big issue is the on/off cycle.

    Which might be your issue. Could the bulbs be going from cold to warm? Just a guess.

    Why not get a Colorstar 3000 or the newer Jobo Colorlines 7000? Very simple to adjust times with height changes. The meter does it for you. You can program various papers into it. The oldest 3000 handles 8 different papers. The newer ones 100. Mark your master print with the areas you read and then just read the same spots.

  8. #18
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    Quote Originally Posted by Nick Zentena View Post
    Longer times won't [or at least shouldn't] hurt your bulbs any. The big issue is the on/off cycle.

    Which might be your issue. Could the bulbs be going from cold to warm? Just a guess.

    Why not get a Colorstar 3000 or the newer Jobo Colorlines 7000? Very simple to adjust times with height changes. The meter does it for you. You can program various papers into it. The oldest 3000 handles 8 different papers. The newer ones 100. Mark your master print with the areas you read and then just read the same spots.
    I second that. I have a Jobo Colorline 5000 that I used for Ilfochrome and it worked great. It requires some calibration and I don't think that the "wheel mechanism" and buttons are intuitive, but the Jobo is excellent.
    Jerold Harter MD

  9. #19
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    Quote Originally Posted by jd callow View Post
    Filter packs will change on longer exposures.
    John;

    I've gotten information from the designers of Endura emulsions who say that the color shift due to reciprocity failure is gone within normal exposure ranges for laser to tungsten light in all sizes. This would be in the range of milliseconds to minutes.

    I have made 8x10 prints and 16x20 prints using the same color balance, merely changing the time / aperature settings to compensate.

    PE

  10. #20
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    Ron,
    My experience is different, although I haven't made a print in 18 months maybe things have changed and or it may have something to do with the lamp output and not the paper.

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