U of S | Mailing List Archive | alt-photo-process-l | Re: green-yellow

Re: green-yellow

Hi Loris,
The colored left of the image, the entire thing, is the "negative" printed on Pictorico (and the blue/green portion of that "negative" is the inversion of the yellow/magenta). The right side of the image is a pt/pd print from that negative. So yes, the pt/pd is completely all done at the same time same everything.

Why yellow is so dense in general and yet so pale, Mark Nelson or Dan Burkholder could answer these questions much better than I, but my guess is that it is because it is opposite the UV spectrum. I'll bring my dots into the BW darkroom this weekend and get another visual in a new process.

Why green holds back more light than pure yellow--again, Mark Nelson or Dan Burkholder can weigh in here? My GUESS would be:
1. more actual ink of cyan and yellow is laid down to get an even color green?
2. the green color blocks out some other wavelength?
3. the process of choice is less sensitive to a particular wavelength?

But one thing that may be the cause of the confusion--the colored dot example has pure magenta and yellow up top (magenta being R255B0G255 and yellow being R255G255B0) which I MIGHT ASSUME (and here I am getting into dangerous territory) is the printer laying down magenta ink only and yellow ink only--no mix. I ASSUME this because my printer, the 2400, has the usual cyan, yellow, and magenta ink along with blacks. But in the bottom green/blue part of the colored dots which is an INVERSION of the top magenta and yellow; the blue dots are not cyan. Cyan measured on the computer screen is R0G255B255 but the blue dot in my example is R0G0B255. However, I do not know, unless I break apart a cyan ink cartridge and paint with it, whether my printer is mixing inks for that color or whether it is the pure ink out of the ink cartridge as is.

Does this make sense? That there are no actual CYAN dots in this example? I'll make one, though :)

I find that in the BW darkroom the yellow still holds true as being dense, as my negatives are red, and the closer to the magenta end of the spectrum I go, the less light is held back. But I never use a pure yellow negative so there is another factor going on than the actual density of the ink, and my first guess would be the printer driver, second the wavelength of light in combination with the sensitivity of the particular process (bw paper being safe under yellow or red light).

Of course, the whole basis of PDN is the response of different processes to different colors which is found in practice and not in theory (if I used theory to inform my practice I'd be a dead duck--thank heavens for those little step wedges and CDRPS and tonal palettes :). I never used blue/purple negs, for instance, until solarplate.

WHEW, Loris, that was a way too long winded answer to your succinct questions.

Please weigh in, Mark and Dan??!!!


Christina Z. Anderson
----- Original Message ----- From: "Loris Medici" <mail@loris.medici.name>
To: <alt-photo-process-l@usask.ca>
Sent: Thursday, April 09, 2009 12:03 AM
Subject: green-yellow

Hi Christina,

I was looking at your visual about colors and UV opacity (here:
http://christinaanderson.visualserver.com/Text_page.cfm?pID=2448) and got
confused a little bit. Are those prints from the same process with same
working paramaters and prodecures?

How Green (which is Yellow + Cyan) can hold back more UV than Yellow
alone, where Cyan is a poor UV blocker (slightly denser than Magenta as
seen from your tests)? My experience with 3 different printers taught me
Yellow is the strongest UV blocker among color inks... How come?


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