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Photo Forum / Film Photography / Darkroom / October 2006Producing Big 16x20 Negatives (Analog Only)
What are the best and or easiest methods of producing large negatives, discounting inkjet or digital methods. Do I have to make an internegative first? The goal is to produce a 16x20 an argyrotype print (monochrome). Thx. p.s. while I'm on the subject ...how do I do a four colour separation using darkroom methods. > p.s. while I'm on the subject ...how do I do a four colour separation > using > darkroom methods. I take it you are separating into CMYK? What are you starting with - color negative, transparency, artwork, color print ...? What is the final output - transparency, bromoil, dye transfer, lithograph ...?  SignatureNicholas O. Lindan, Cleveland, Ohio Darkroom Automation http://www.nolindan.com/da/index.htm n o lindan at ix dot netcom dot com > > p.s. while I'm on the subject ...how do I do a four colour separation > > using [quoted text clipped - 7 lines] > What is the final output - transparency, bromoil, dye transfer, > lithograph ...? More interested in the monochrome negatives right now, but sure, can I make four colour separations in my darkroom with a dichro head? As mentioned in the original Argryotype for monochrome, I'm probably thinking gum for the four colour. Alan Smithee a écrit : > What are the best and or easiest methods of producing large negatives, > discounting inkjet or digital methods. Do I have to make an internegative > first? The goal is to produce a 16x20 an argyrotype print (monochrome). Thx. > p.s. while I'm on the subject ...how do I do a four colour separation using > darkroom methods. I'm not really an alternative photography specialist but found this link on argyrotype: http://www.ephotozine.com/techniques/viewtechnique.cfm?recid=135 Looks like you need a real negative with a density range of around 2.2. So, if you're starting from a negative, you have to make an "interpositive" enlarged on you final 16x20 negative. You'll also need to adjust the contrast of the final negative to the value mentioned above. Use a step tablet for this job. I haven't checked the price for 16x20" negatives but I suspect they should be very high. I don't know if a paper negative can be used as the exposure light should be rich in the UV spectrum. That's one reason why so many use digital negatives (either inkjet or made through an imagesetter). A second reason, is that they use a mix of colors, not only black, to increase the UV density of the neg as most of the alt processes require pretty contrasty with long scale negatives. Regarding color separation, it's usually a 3-color separation (also called trichromy), either RGB or CMY. Your color head has probably the CMY filters, so you can do it. It's pretty common with gum and for your gum print you'll have to use CMY pigments. The separation is done by exposing 3 negatives each one through one of the CMY filters, then you'll have to coat your print with one layer including, say Cyan pigments, expose it with the "cyan" negative, develop it, and do the same with the magenta and yellow layers. The exposure and contrast of each negative is important as is the quantity of pigments in each layer and the way you'll develop them. Anyway, the lack of precision is part of the interest in such processes. I suppose it's easier to start from a positive (a slide) as it already has a high contrast and no orange mask like with color negatives. Good luck, Claudio Bonavolta http://www.bonavolta.ch Claudio Bonavolta a écrit : > Alan Smithee a écrit : > [quoted text clipped - 44 lines] > Claudio Bonavolta > http://www.bonavolta.ch I forgot to mention that you can add the black channel by making a 4th negative without filtering and using black pigments or ink ... Claudio Bonavolta http://www.bonavolta.ch > What are the best and or easiest methods of producing large > negatives, discounting inkjet or digital methods. Do I have to make > an internegative first? The goal is to produce a 16x20 an argyrotype > print (monochrome). Thx. p.s. while I'm on the subject ...how do I > do a four colour separation using darkroom methods. Digital and an inkjet onto Pictorio OHP is by FAR the best way to go. Look for `Precision Digital Negative' by, I think, Nelson. SignaturePaul Repacholi 1 Crescent Rd., +61 (08) 9257-1001 Kalamunda. West Australia 6076 comp.os.vms,- The Older, Grumpier Slashdot Raw, Cooked or Well-done, it's all half baked. EPIC, The Architecture of the future, always has been, always will be. |
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