Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,863   Posts: 1,583,184   Online: 798
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 17
  1. #1

    Join Date
    Feb 2010
    Shooter
    Medium Format
    Posts
    98

    Contact print max glass size

    Hi All,

    I just have a 8X10 spring loaded contact frame. I ultimately want to go bigger and have read that 8X10 is really the limit for contact printing frames. Is this true? Would say 2 ~16X20 1/4 inch sheets of glass with regular (rubber feet) clamps provide enough pressure for a reasonable print or would i really be pushing it? This would be for pd/pt printing.

    Thanks

  2. #2
    Shawn Dougherty's Avatar
    Join Date
    Jul 2004
    Location
    Pennsylvania
    Shooter
    Multi Format
    Posts
    4,141
    Images
    298
    You can get much bigger frames from many different places. Do a google search, do an apug search. You'll find lots of examples, suggestions and prices.

  3. #3
    Nicholas Lindan's Avatar
    Join Date
    Sep 2006
    Location
    Cleveland, Ohio USA
    Shooter
    Multi Format
    Posts
    2,381
    Images
    4
    I have an 11x14 that works tolerably well.

    The key to contact printing is the psi [pounds per square inch/pressure]. 16x20 is 320 sq inches - to apply a pressure of 1/2 psi (a not-too-well filled party balloon's worth - about what most frames can manage) you would need 160 pounds of clamping force.

    You only need one sheet of glass. You can make the backing from 3/4" plywood. You will need to cover the plywood with thick felt. A frame around the glass will help to distribute the pressure from the clamps.

    Large contacting frames use vacuum to clamp. One side of the frame is glass, the other has a rubber blanket attached to it. Air is evacuated and the blanket clamps the artwork to the glass with atmospheric pressure - 14 psi. A 16x20 frame would have over 2 >tons< of total clamping force. With the rubber blanket there is no net force on the glass. There are contacting schemes that use a box with holes as the evacuated side and a thin sheet of plastic that goes over the artwork to allow evacuation of the space between the a/w and the film.

    You used to be able to get contacting frames for free as print shops were converting to digital and 'laser plates' right and left. You can find them on ebay - the larger ones cost much less than the smaller ones. And they weigh a ton [almost literally for the large 40x48" ones]. Search for "vacuum frames" and "exposure units".
    Last edited by Nicholas Lindan; 02-18-2013 at 06:49 PM. Click to view previous post history.
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  4. #4

    Join Date
    Mar 2005
    Shooter
    ULarge Format
    Posts
    873
    Images
    24
    I have a spring back 16x20 frame that I got from B&S. It works fine. I also have a much larger frame that I hand built. I do 20x24 inch prints with it. I had 4 custom springs fabricated for it by a local metal shop. It is fine for pt/pl prints.

  5. #5
    Mainecoonmaniac's Avatar
    Join Date
    Dec 2009
    Shooter
    Multi Format
    Posts
    3,192
    Images
    6
    I made a 20x24 for my light box. I ripped the molding on my table saw out of oak and used scrap plywood with felt for the back. It cumbersome. I'm thinking of making a smaller one.
    "Photography, like surfing, is an infinite process, a constantly evolving exploration of life."
    Aaron Chang

  6. #6
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,540
    Images
    65
    The Formulary sells them up to 20x24. They are very well designed.

    http://stores.photoformulary.com/-st...ame/Detail.bok

    PE

  7. #7
    DWThomas's Avatar
    Join Date
    Jun 2006
    Location
    SE Pennsylvania
    Shooter
    Multi Format
    Posts
    2,272
    Images
    67
    I might think a thin layer of foam of other elastic material on top of a sturdy piece of plywood (maybe 3/4 birch) would help to take up any surface irregularities to promote solid contact. One would want relatively thick glass (or maybe acrylic) so as not to have it explode from the force. Wingnuts and bolts, or some toggle clamps, could be used to clamp the frame.

    Heh, I think I have a 2 1/4 x 3 1/4 Kodak contact frame somewhere that's been in the family since 19-ought-48 or so. (Velox and a Tri-Chem Pack anyone. )

  8. #8
    Ken Nadvornick's Avatar
    Join Date
    Mar 2005
    Location
    Monroe, WA, USA
    Shooter
    Multi Format
    Posts
    3,637
    Images
    48
    For vacuum frames, there's these from Edwards Engineered Products:
    Vacuum Contact Printer Frames

    For magnetic frames, there's these from APUG advertiser Alistair Inglis:
    Magnetic Contact Printer Frames

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    — Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  9. #9
    richard ide's Avatar
    Join Date
    Nov 2005
    Location
    Markham, Ontario
    Shooter
    Multi Format
    Posts
    1,216
    I had a 66" x 96" vacuum contact frame and I have seen one 24' long.
    Richard

    Why are there no speaker jacks on a stereo camera?

  10. #10

    Join Date
    Feb 2010
    Shooter
    Medium Format
    Posts
    98
    Thank you everyone. I think my follow on question is where would I see a decrease in quality above 8x10?

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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