U of S | Mailing List Archive | alt-photo-process-l | Re: Paper negatives- Ink Selection

Re: Paper negatives- Ink Selection

On Oct 12, 2008, at 11:23 AM, Loris Medici wrote:

I use the grayscale using all inks (not black and gray - if present - inks
only), plus, I choose plain paper as the media. Fortunately, with my inks
the printer lays just enough ink giving an almost perfect negative in
terms of density range (something around log 1.0), and the curve I use for
gum prints are is the least drastic and most smooth one among my curves
collection for many processes and paper. In fact, I think that's why other
people's exposure times are considerably longer compared to mines... (!?
Loris, I'm wondering what data you're basing this last bit on, that other people's exposure times are longer than yours. It's generally not useful to try to compare exposure times because there are so many variables involved, but putting that aside for a moment, I've looked back through this thread, and the only reference to exposure times I can find is Guido's comparison between oiled and unoiled Epson PQ paper, 8 vs 48 minutes, with cyanotype. Since it was cyanotype, and since the paper is a heavier paper (27 pounds) than yours, it's not surprising that his exposure time for unoiled paper would be longer than yours, and we haven't even got to light source yet; to reach immediately to curves to account for a difference in exposure times seems rather a long stretch to me.

Perhaps I've missed other posts that included exposure times for gum and paper negatives (my server doesn't accept some of the alt-photo mail, so I don't always see all the posts). At any rate, my times with oiled paper negatives run close to my times with inkjet transparencies, about 3 minutes, to add to your database on exposure times. I don't have any comparison with unoiled paper to offer, because that's not an option that makes any particular sense to me.

But be that as it may, I can't see any reason why curves would account for a difference in exposure time. After all, the exposure time is determined before curves are even calculated, at least that's how it is with the system I use, and I assume it's the same with all systems; the curve doesn't change the exposure time. Besides, curves simply redistribute the tones within the print tonal range that particular emulsion can print under that particular protocol; they don't extend it, so there's no logical reason curves would have any effect on exposure time.