How about some basic info about creating an internegative?

Discussion in 'Alternative Processes' started by cloudhands, Apr 15, 2009.

  1. cloudhands

    cloudhands Member

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    Hi, I'm sorry if this question has been asked before. I'm curious to try some gum bichromate printing. I want to do something with the slide film I've shot, other than project them against my living room wall (don't get me wrong, I dig it).

    I want to create internegs from slide. I shoot 35mm and would like to make 8x10 internegs for the gum bichromate process.

    What sheet film should I buy for this? How should I work the exposure? Development? I have a color enlarger (additive). What exposure times should I use?

    Thanks!
     
  2. Mike Wilde

    Mike Wilde Member

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    Interneg film - now discontinued - was a low contrast panchromatic film. I have read of unsharp masking in Photo Techniques magazine Howard Bond (2006-2008 I think) using TMAX 100 where panchromatic masks were required. It is possible to do this striaght to 8x10, but it is an expensive way to go.

    I would suggest that you make an interneg using a pan b&w film; tmax is exceptionally fine grained and would work well. Calibrate your process. You need to make tests to figure out your real film speed, to get (in you case) the slide shadows off of the toe of the tmax film. Then you want to develop to expose properly and develop to a moderate contrast, to stay in a linear portion of the interngative HD curve.

    You may need to pre, or post flash the interneg film to reduce contrast. This is most easily achieved in a slide duper, like a Bowens Illumitran, staying with 35mm.

    Once you have the now b&w interneg, than you can work with orthochromatic 8x10 (cheaper than pan film and easier to work with, under appropriate safelight), or larger, film to make the large postive, then contact it for the chrome contact neg.
    There are other options, such as reversal at the 35mm interneg stage, or reversal once you go to the full size contact sheet.

    Here lith film is just the thing. Something like Freestyle APS I think. I have a freezer stash of some old graphic arts stuff, so I have not been looking lately. It can be developed in Dektol, or D-76 , or weak dilutions of hc110 etc to get continuous tone results from Lith film.

    Your best friend though this process will be a step wedge. It will let you see what the contrast range and scale expansion/contraction you are dealing with, at each stage.
     
  3. keithwms

    keithwms Member

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    Yep, I use tmax.
     
  4. 36cm2

    36cm2 Member

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  5. nawagi

    nawagi Member

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    Check out www.digitalnegatives.com. While APHS will make fine internegs (used dektol 1:10),
    scanning your slides and photoshopping separations with ink jet output to Pictorico OHP film provides excellent controls - plus you can go straight from slide to negative without the interneg.

    NWG
     
  6. cloudhands

    cloudhands Member

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    Hey, thanks for the replies, fellas! I'm afraid this might still be out of my range of darkroom technique at this point, but please humor me as I have more dumb questions:
    - If I start with a slide, enlarge it onto tmax and then contact print to an ortho film, I will end up with a positive, right? I thought contact printing in alternative processes used a negative.
    - How can I figure out exposure times? My enlarger doesn't have 1/250sec or whatever increments. It starts at 5 seconds, then goes up by 1 second increments.

    36cm2 thanks, I did find that article, and was hoping for a bit more detail. This is the part I am interested in:
    "By starting with a positive transparency from the camera an enlarged internegative can be obtained in one step on sheet film. If the original small-format image is a colour transparency, projection onto orthochromatic materials (which are insensitive to red light) will not faithfully reproduce the tonal balance. To maintain this, a panchromatic sheet film will be necessary, possibly with a colour head or a filter to bring the enlarger light source to a daylight colour balance."

    Tmax is a panchromatic sheet film, yeah? I have a color head. What does it mean to "bring the enlarger light source to a daylight colour balance?"

    I assumed (naively, apparently) that the process would be something like:
    -set up enlarger for 8x10 projection size
    -switch off two colors (I have an additive enlarger, so red-blue-green)
    -expose a sheet of film, put that sheet in a dark box, marking it somehow to indicate the color exposed
    -repeat for the other two colors
    -develop the 3 sheets
    -contact print using the gum bichromate process

    This is not going to give me the results I need?


    Thanks for clearing this stuff up for me.

    edit: yeah, and I don't have a scanner, so I'm totally analog in this process
     
  7. Jim Noel

    Jim Noel Member

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    AN oft repeated error is in play here. Yes, dilute paper developers work with lith type films, but not nearly as well as dilute film developers. Paper developers by their nature are more active and will produce more contrast than film developers.An inter-positive needs to be very low in contrast. It should have grayish highlights and very open shadows. This is quite easily done if film developers are used. D23 works well, as do D76 diluted one to five, and HC 110 diluted one to 20 from stock.
     
  8. Mike Wilde

    Mike Wilde Member

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    good luck -mike
     
  9. cloudhands

    cloudhands Member

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    Great. I think I am getting closer to wrapping my head around this.
    I am aiming for full color gum prints, kinda like doing a 3-pass silkscreen print. Yellow first, then blue, then red is what I have read somewhere.
    I guess I will buy a box of Tmax in 8x10 to produce 3 separation negatives from my 35mm positive.
    Now I need to figure out how to do the exposures for the sheet film using my enlarger. I guess I will just stop down on the enlarger lens and take a reading with my spot meter? I do have a polarizer but no ND filters, save a ND Grad filter. Maybe I will just hold the polarizer up against the enlarger lens. Hopefully that will provide me with a low enough light level to give 5 seconds or more exposure on the sheet film.

    Does this sound like it will work? 8x10 sheet film is expensive, I don't want to make too many mistakes with this.

    Thanks again for all your help.
     
  10. PVia

    PVia Member

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    That is going to cost you a lot in terms of film and the learning curve...it will take you a while to master this. Use the Arista Litho film to get your process down for now....