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

Re: Paper negatives- Ink Selection

Katharine, don't worry I'm pretty careful about this subject - knowing (by
experience) you'll chime in every time it's brought up, to clarify ;) I'm
getting older I guess; less and less surprises... ;)

I wasn't attributing the short exposure I'm using to curves at all, that
was a side note (which should have been enclosed between parenthesis,
sorry). I was trying to say (indirectly) that since the DR (=density
range) and tonal progression of my paper negatives (made with the HP 9180
all-inks grayscale setting, using the printer's plain paper profile) are
close to ideal (in tricolor gum printing context - which is supported by
the fact that the curve I devised for this particular combination is the
smoothest and least dramatic one among all curves I did until now),
therefore, other people's longer exposure times could be caused by the
fact that they're using negatives with more DR, which naturally will
require more exposure and a stronger / more dramatic curve to
counterbalance. Or they're not calibrating, or their calibrations are

Hope it's clear, and makes more sense to you now. I perfectly understand
the confusion I may have caused on your part.


P.S. BTW, I have compared my times with the times of people who use
similar light source, emulsion, negative media and working procedures. I'm
perfectly aware of the parameters affecting exposure time and pay
attention to them.

14 Ekim 2008, Salı, 7:18 pm tarihinde, Katharine Thayer yazmış:
> 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.
> Katharine
> 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...
>> (!?