Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,568   Posts: 1,573,487   Online: 840
      
Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 39

Thread: Gum Bichromate

  1. #11

    Join Date
    Sep 2005
    Shooter
    Medium Format
    Posts
    43
    Images
    1
    Here's how I would start: Convert the image to CMYK. Invert the image. Split channels, print and label the negatives. Start with the Cyan, then Magenta then Yellow then Black. Unless you have a totally mechanized approach, your development will require some observation to determine when a particular layer has cleared. This would be difficult to do if black were your first layer. Many gumprinters never use black (and the forums would get heated at times regarding this). I DO use black, but I always put in on last, because this allows me more control.

  2. #12

    Join Date
    Nov 2005
    Location
    Los Angeles, CA
    Shooter
    Multi Format
    Posts
    5,223
    Quote Originally Posted by GumPhoto View Post
    While Brian's suggestion has merit, I found it did not work for me, as my initial attempts at monochrome were quite dismal. What you might want to try is an approach I have used in workshops: print separation negs, but then use them to print three layers of the same monochrome color. When you start getting some positive results, then ...
    I'm in complete agreement, with one exception. Why not do this with a regular B&W neg to get an understanding of the various gum printing variables and registration? Why hassle with separation negs until those basics are well understood?

  3. #13

    Join Date
    Jun 2006
    Shooter
    35mm
    Posts
    35
    Quote Originally Posted by vintagepics View Post
    So I assume I digitize the print i want to make. In Photoshop i convert the color image to a color negative. Seperate them in channels to CMYK, then print each channel as a B&W transparency. Then through whatever registration system I come up with, print each layer, probably starting with black (K). At printing time do I then use the C layer to print the blue, M red, and Y yellow?
    Thats correct. However if you use rgb instead of cmyk, the you will use the complementary colour ie
    R = Cyan
    G= Magenta
    B= Yellow
    What's wrong is wrong even if everyone does it. What's right is right even if nobody does it.

  4. #14

    Join Date
    Apr 2008
    Location
    Santa Cruz, CA
    Shooter
    Multi Format
    Posts
    167
    Images
    17
    Quote Originally Posted by BrianShaw View Post
    I'm in complete agreement, with one exception. Why not do this with a regular B&W neg to get an understanding of the various gum printing variables and registration? Why hassle with separation negs until those basics are well understood?
    +1

    Start making gum prints and get a feel for the process.

  5. #15
    vintagepics's Avatar
    Join Date
    Apr 2006
    Location
    Maryland
    Shooter
    Large Format
    Posts
    93
    Images
    15
    I agree with all. Here is what I did just to get my feet wet. I ordered two kits from Adorama, one for doing black gums, and one for doing color gums. It says each kit will do fifty 8x10 gums. I will start with the black and work my way into the color once I get the understanding. I like jumping the gun a bit on the learning curve. Have any of you had any experience with these kits?

    Rick
    Rick Lanning
    Retired Crime Scene Photog.

  6. #16

    Join Date
    Sep 2005
    Shooter
    Medium Format
    Posts
    43
    Images
    1
    Quote Originally Posted by BrianShaw View Post
    I'm in complete agreement, with one exception. Why not do this with a regular B&W neg to get an understanding of the various gum printing variables and registration? Why hassle with separation negs until those basics are well understood?
    No reason not to. It seemed like the OP wanted to do full-color and I thought starting off with separation negs could be the faster approach. AND the subtle differences in the multiple monochrome layering does provide a nice end result. Taking an approach like this encourages the print to be "built", which is the same tactic taken with full-color gums. But using one negative is certainly easier. Registration will still be an issue.

  7. #17
    TheFlyingCamera's Avatar
    Join Date
    May 2005
    Location
    Washington DC
    Shooter
    Large Format
    Posts
    8,476
    Blog Entries
    51
    Images
    437
    I've never used the Adorama kits. I didn't even know they offered one. I've been buying my materials for gum from Bostick & Sullivan for the most part, except my pigments and occasionally my paper from Utrecht.

  8. #18

    Join Date
    Nov 2005
    Location
    Los Angeles, CA
    Shooter
    Multi Format
    Posts
    5,223
    Quote Originally Posted by vintagepics View Post
    I like jumping the gun a bit on the learning curve.
    Sometimes that can be a great personality trait! Good luck with your new venture!

    What are you using for a light source and negative registration method?

  9. #19
    artonpaper's Avatar
    Join Date
    Aug 2007
    Location
    Brooklyn, NY
    Shooter
    Multi Format
    Posts
    325
    Images
    135
    Quote Originally Posted by Mainecoonmaniac View Post
    I think RGB is for mixing colors with light, but CYMK is for mixing inks. An example are computer files are RGB, and printing presses have Cyan, Magenta, Yellow and Black or K which means keyline.
    This is true and photoshop does have a CMYK work space. But if one separates the channels in RGB then inverts those to negatives, those negatives can be printed in their complimentary colors, Red to cyan, green to magenta, and blue to yellow. It's also true that without a K or black negative, the shadows may be muddy. A K negative is most easily obtained in CMYK.

    In addition, I think it very good advice to start with monochrome. I don't think gum is for four-year-olds. It is necessary to learn the technique and establish a good exposure range, and pigment to gum mixes.

  10. #20
    vintagepics's Avatar
    Join Date
    Apr 2006
    Location
    Maryland
    Shooter
    Large Format
    Posts
    93
    Images
    15
    Quote Originally Posted by GumPhoto View Post
    No reason not to. It seemed like the OP wanted to do full-color and I thought starting off with separation negs could be the faster approach. AND the subtle differences in the multiple monochrome layering does provide a nice end result. Taking an approach like this encourages the print to be "built", which is the same tactic taken with full-color gums. But using one negative is certainly easier. Registration will still be an issue.
    Full color is my goal, especially the color stylings of the old 1940s post cards, but I don't mind starting at the bottom. B&W is still a true love.
    Rick Lanning
    Retired Crime Scene Photog.

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