Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,765   Posts: 1,516,353   Online: 1013
      
Results 1 to 4 of 4
  1. #1

    Join Date
    Feb 2009
    Shooter
    Medium Format
    Posts
    40

    Carbon process. Why contact print?

    In carbon process, why is it required that the paper be exposed in contact with an enlarged negative?

    Could not an enlarger be used to make the final print, if it were fitted with the appropriate light source?

  2. #2
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,172
    Images
    148
    The Gelatin needs UV exposure via the sun or a UV light source and you would need special lenses for an enlarger with a UV light source. Camera lenses for UV work are(?were) made for scientific use but because they use specialist glasses that makes them expensive.

    It's the same reason Silk screen printing needs a UV light source.

    Ian

  3. #3

    Join Date
    Mar 2003
    Location
    Greenville, SC
    Shooter
    Large Format
    Posts
    4,813
    Images
    5
    Quote Originally Posted by cinefane View Post
    In carbon process, why is it required that the paper be exposed in contact with an enlarged negative?

    Could not an enlarger be used to make the final print, if it were fitted with the appropriate light source?

    Most alternative processes, including carbon, have very low sensitivity to light. Figures I have seen suggest that the sensitivity of dichromate colloids is about a million times less than that of silver bromide enlarging papers, and thousands of time less than silver chloride papers like AZO and Lodima. This makes enlargement impossible, or at least very impractical, since you would need a light source high in UV radiation of around 10,000 to 20,000 watts.


    Sandy King
    Last edited by sanking; 07-13-2009 at 12:45 PM. Click to view previous post history.

  4. #4
    2F/2F's Avatar
    Join Date
    Apr 2008
    Location
    Los Angeles, CA
    Shooter
    Multi Format
    Posts
    8,008
    Images
    4
    Usually, if something needs to be contact printed, it is because it reacts very slowly to light.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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