Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,904   Posts: 1,584,585   Online: 900
      
Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 31
  1. #11
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,883
    I have a timer that can do .1s. I suppose I want to make a step exposure from white until black, then try the same regimen with different filters? You're right, that does sound like a lot of work.

  2. #12
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,835
    Images
    1
    Quote Originally Posted by BetterSense View Post
    I have a timer that can do .1s. I suppose I want to make a step exposure from white until black, then try the same regimen with different filters? You're right, that does sound like a lot of work.
    Exactly. The same can be done with one exposure by using a Stouffer step tablet. I suggest to invest in one. It's a small long-time investment with long-time benefits.
    Regards

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

  3. #13

    Join Date
    Jun 2004
    Location
    South Norfolk, United Kingdom
    Shooter
    Multi Format
    Posts
    2,918
    Images
    66
    Ralph,

    I presume one can make best use of the Stouffer transmission projection step wedges in conjunction with a densitometer in order to access paper and process characteristics.

    Tom.

  4. #14
    Nicholas Lindan's Avatar
    Join Date
    Sep 2006
    Location
    Cleveland, Ohio USA
    Shooter
    Multi Format
    Posts
    2,381
    Images
    4
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  5. #15
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,883
    Well I just wasted about 4 decades in the old dark room, printing up a primitive test of my contrast filters, with completely inconclusive results. If you would like to speculate on the results you are welcome to. I think I need to budget a step wedge and in the meantime just figure if it don't print on grade 2, wait.

    I printed, from top to bottom, .1, .2, .4, 1, 2, 4, 10, 20, 40, and 80 second exposures. 10 seconds is the first tone that showed up. From left to right, the grade 0, 1, 3, 4, and 5 filters.


  6. #16
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,835
    Images
    1
    Nicolas

    Thanks for sharing. The ISO standard sets the speed point to 0.6 >b+f. Your data points tell a different story. They are pretty much all over the place. It hard to make out an accurate intersection point. Ilford's own product literature shows a much better fit to the ISO standard. So did (does) the Agfa and Kodak literature, by the way. My own data, also shows little to no deviation from the manufacture data or the standard. I don't know where your deviation comes from, but these are very rough data curves.

    The difference might be that I judge the intersection point(s) after applying a best-fit curve through the data points. Best-fit equations for s-shaped curves are not trivial. I can share my empirical equations with you. They were evaluated by Ilford's Technical Department a while back, and they were impressed with how close the data fit was, especially at toe and shoulder. However, I don't think Excel can handle them. You might need a dedicated graphing program.

    Different people taken similar measurements often get very different results. Potential sources for variation might be the spectral sensitivity of the densitometer. The red-content in toned or warm-tone papers was too much for my old Agfa densitometer and always gave skewed results. Other issues are often within the consistency of testing. Test exposures should not be collected and then develop together. That alters the results. Just a few thoughts, the list goes on as you probably know. Again, I can't tell where the difference comes from. Maybe you can share how you did your tests in detail.

    However, for this conversation it doesn't matter where the speed point is, because it rarely is where we need it to be for an exposure-correction-free contrast change anyway. Nothing beats a well-made test strip.
    Regards

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

  7. #17
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,835
    Images
    1
    Quote Originally Posted by Tom Kershaw View Post
    Ralph,

    I presume one can make best use of the Stouffer transmission projection step wedges in conjunction with a densitometer in order to access paper and process characteristics.

    Tom.
    Yes, Tom

    But you can make a lot of use of them without a densitometer too. I can tell you, fr example, what ISO grade your filter/material combination produces with a step tablet and without a densitometer. No sweat!
    Regards

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

  8. #18
    RalphLambrecht's Avatar
    Join Date
    Sep 2003
    Location
    Central florida,USA
    Shooter
    Multi Format
    Posts
    6,835
    Images
    1
    Quote Originally Posted by BetterSense View Post
    Well I just wasted about 4 decades in the old dark room, printing up a primitive test of my contrast filters, with completely inconclusive results. If you would like to speculate on the results you are welcome to. I think I need to budget a step wedge and in the meantime just figure if it don't print on grade 2, wait.

    I printed, from top to bottom, .1, .2, .4, 1, 2, 4, 10, 20, 40, and 80 second exposures. 10 seconds is the first tone that showed up. From left to right, the grade 0, 1, 3, 4, and 5 filters.

    I agree, inconclusive. You might need to budget for a new set of filters too.
    Regards

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

  9. #19
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    6,387
    Maybe its not MG paper? I would think the filters would have all faded the the same pale color to produce those results.

  10. #20
    BetterSense's Avatar
    Join Date
    Aug 2008
    Location
    North Carolina
    Shooter
    35mm
    Posts
    2,883
    It was fresh MGIV paper. All were exposed on the same sheet, developed at the same time.

Page 2 of 4 FirstFirst 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin