Re: another 3 layer gum attempt
Hi Joe / Paul, I use negatives with a DR of log 1.5 for gum. (DR is absolute dmax - dmin of negative in this context; nothing related to zones...) That is exactly what I need for 2A+1B traditional cyanotype -> because I don't calibrate for gum, I just use negatives calibrated for 2A+1B cyanotype when printing gum. Works extremely well. (And is very practical to me since I often combine gum and cyanotype so I don't have to print two separate negatives for that purpose...) As a matter of fact I couldn't get satisfactory shadow detail with lower DR negatives. (That is thin negatives, something like log 0.9 - 1.0 as suggested by many others...) Anyway, that's me, my incompetence(!) ;) -> see it for yourself. Will let Christina write about it (since she has vast experience/knowledge about calibrating diginegs for gum), but I should mention that "to me" it's a tiring process which in the end you have to act within very specific limits, taking out a lot of the flexibility gum printing provides... Regards, Loris. -----Original Message----- From: Joseph Smigiel [mailto:jsmigiel@net-link.net] Sent: Wednesday, July 22, 2009 3:14 PM To: alt-photo-process-l@usask.ca Subject: Re: another 3 layer gum attempt ... If you were to consider how Arentz et al would describe the DR (as I understand his description from 90% black to threshold light gray inclusive, i.e., steps 3-5 as a gum emulsion might print with a maximum of steps 1-6 distinct) the gum negative density range might only be (5-3) x 0.15 = 0.30 and that ain't much. You really need a thin, flat negative compared to other processes. Christina Anderson has done some wonderful work in gum using Mark Nelson's PDN system to calibrate everything in the digital environment. Perhaps she'll chime in here with some digineg advice.
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