How multigrade paper works

Discussion in 'B&W: Film, Paper, Chemistry' started by Young He, Mar 4, 2018.

  1. Young He

    Young He Member
    Ads Enabled

    Messages:
    77
    Joined:
    Aug 30, 2017
    Location:
    Houston
    Shooter:
    35mm
    Hello all,

    I am somewhat curious about how multigrade paper works. I am aware that the paper uses two different emulsions with different sensitivities and contrasts mixed together or coated in a multilayer. However, is it possible to make a rudimentary multigrade paper with two emulsions that are the same contrast and are only sensitized to different wavelengths?
     
  2. NedL

    NedL Subscriber
    Ads Enabled

    Messages:
    2,706
    Joined:
    Aug 23, 2012
    Location:
    Sonoma County, California
    Shooter:
    Multi Format
    Groups:
    Often three kinds of emulsions. This document explains it pretty well.

    I think the theoretical answer to your question is "yes", but in practice it is difficult to make an emulsion that is not sensitive to blue and UV. So in practice, the different emulsions that make up multigrade paper instead have differing sensitivities to longer wavelengths of light. Then the curves are "tuned" so that the contrast transition is reasonably smooth.
     
  3. AgX

    AgX Member

    Messages:
    18,217
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    No.
     
  4. MattKing

    MattKing Subscriber
    Ads Enabled

    Messages:
    23,756
    Joined:
    Apr 24, 2005
    Location:
    Delta, BC, Canada
    Shooter:
    Multi Format
    The two (or more) emulsions have the same contrast.
    They have different speeds, and contrast is controlled and achieved by adding their respective built densities.
    Read about it in Mr. Lindan's excellent article from his Darkroom Automation site: http://www.darkroomautomation.com/support/appnotevcworkings.pdf
     
  5. OP
    OP
    Young He

    Young He Member
    Ads Enabled

    Messages:
    77
    Joined:
    Aug 30, 2017
    Location:
    Houston
    Shooter:
    35mm
    Ok. Thank you for the information.
     
  6. AgX

    AgX Member

    Messages:
    18,217
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    There have been made most different approaches to yield a variable contrast paper.
    My answer was "no", as I assumed the average reader would understand with "same contrast" something different than finally applied by Ilford.
    The author of the linked dokument is erronous or at least misleading in a major point.
     
  7. john_s

    john_s Subscriber
    Ads Enabled

    Messages:
    1,236
    Joined:
    Nov 19, 2002
    Location:
    Melbourne, A
    Shooter:
    Medium Format
  8. twelvetone12

    twelvetone12 Member

    Messages:
    552
    Joined:
    Feb 16, 2015
    Location:
    Over the Alps
    Shooter:
    35mm
    which point? (no polemic, I'm genuinely interested)
     
  9. RalphLambrecht

    RalphLambrecht Subscriber
    Ads Enabled

    Messages:
    10,723
    Joined:
    Sep 19, 2003
    Location:
    K,Germany
    Shooter:
    Medium Format
    let's leave that for PE to answer.
     
  10. AgX

    AgX Member

    Messages:
    18,217
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    There is a 80 years history to contrast variable materials. And Ilford themselves started with two emulsions of different contrast. Only recently, with type 4 they changed that.
     
  11. RauschenOderKorn

    RauschenOderKorn Subscriber

    Messages:
    554
    Joined:
    Apr 14, 2016
    Location:
    Bavaria, Germany
    Shooter:
    Medium Format
  12. jvo

    jvo Subscriber
    Ads Enabled

    Messages:
    800
    Joined:
    Dec 6, 2008
    Location:
    left coast of east coast
    Shooter:
    Medium Format
    it's done with precise mix of pixie dust, shamanism, and enchantment.:surprised:
     
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies. If you have a Photrio account, please log in (and select 'stay logged in') to prevent recurrence of this notice.