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

Re: green-yellow

Absolutely yellow is always densest for me too with Epson 2200, 2400, 4000, 4800, 3800. I just can't answer why. But in combination with cyan, it usually is the most opaque and I don't know why (not in the BW darkroom of course).

I know that PDN uses color as filters of light, not just opacity to light, like a filter on the front of the camera lens (being that the color of the filter allows itself in but blocks its opposite so yellow filters will make yellow objects lighter in the final BW print (because the negative will be denser at that point) and blue skies darker (because the blocking of blue light will make the negative less dense at that point)).

And that is with a panchromatic film, not with an orthochromatic bw paper so then things get more complex, as they do with alt processes that are responsive to different wavelengths as well.

The conundrum for teaching, too, is that light opposites are not pigment opposites--another thing students never get. Yellow is opposite blue, Green magenta, and red cyan instead of yellow/purple, green/red and blue/orange in pigment. And that red and green light together make yellow and yellow is not a pure color!! It makes sense that red and blue light make magenta light and blue and green make cyan light but not red and green make yellow light!

And that the "blue" in blue light is NOT cyan blue but a really gorgeous royal blue!

Oh my goodness, well, you get what I'm trying to say and I know you know all this stuff anyway...but it is soooo confusing to a twenty-something.

Now that our color processing machine is dismantled, students do not have the practical experience of using filters under the enlarger to see all this stuff.

But you made me realize what I really need to do is do a visual of RGB and CMY big dots and then print it in each process to elucidate how differently the inks work and how process-dependent they are as well.

When above is analyzed, it can be seen that Cyan is definitely more opaque
for UV light than Magenta is... (Magenta patch is darker than Blue patch!)

For me, 3 different printers / 3 different inksets and Yellow was always
the most opaque/dense color. (Against Green and others.)

Thanks for the long answer.

9 Nisan 2009, Perşembe, 4:46 pm tarihinde, Christina Z. Anderson yazmış:
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
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
that it is because it is opposite the UV spectrum.  I'll bring my dots
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
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
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
ink only--no mix. I ASSUME this because my printer, the 2400, has the
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
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,
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
go, the less light is held back.  But I never use a pure yellow negative
there is another factor going on than the actual density of the ink, and
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
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

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
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?