Judy Seigel (jseigel@panix.com)
Wed, 06 Jan 1999 14:39:18 -0500 (EST)
PS: There'a a fact at the end of this message, so if the subject interests
you, keep going!
================================
I had been wondering if I could really print 3 or 4-color gum to close
enough tolerances so the Photoshop color separation settings would make a
significant difference. This is an entirely different matter from the old
"gum can't do fine detail" myth, which grew in the Petri dish of
cut-and-paste murk. Gum, as I may have said a time or 20, can get
everything in the negative if you let it.
But mixing, coating & developing color from paint, and by hand, rather
than machine, is in my experience unlikely to match the calibrations
assumed in offset printing. Just the difference between measuring a half
gram and a half gallon of color is overriding, and I suspect the
transparency of paint, even "transparent" color, is not like the sinking
in, or actual absorption of one layer by another in the printing ink. With
gum, each layer must be dry & hard before you add the next. Or that's my
surmise, an attempt to explain the differences.
So I printed out 4 sets of separations by laser on plain paper & waxed
them: one with a Medium Black separation, one with Light Black, one with
no black (strangely, on this one the image turned all black, but the 3
separations did appear), and one set for undercolor removal (UCR), rather
than the default Grey Component Replacement (GCR).
Differences to the eye from the printed separations range from hardly
perceptible to distinctly distinct -- but how they will translate into a
print remains to be seen. Experience suggests that in any event they may
LOOK best without the black, so I guess I'll have to try both versions.
Pete's advice about using complementary colors helped me out of one
pickle, by the way (thanks!). I'd been reproaching myself for timidity in
not doing a black layer... finally in a print with an area imitating a b&w
photo I just laid it on---- yuck! The ugliest thing I ever saw in my
studio. (It was "Neutral Tint" which the book says is a black.) So I began
adding complements, which took the curse off, but it would still seem that
the black should go on first. (This was on top.) A while back I tried a
Mars Black watercolor, which didn't work with gum, although Mars black was
the best black in acrylic, which I assume is what Peter is using. Oh dear,
another variable ...;- (
OK, sorry for digressing, here's the fact, found in the Photoshop 4
manual, page 97:
Because non-PostScript color printers (such as HP Deskjet, Canon
Bubblejet, and Epson Color Stylus) generate their own black values, the
Separation Setup settings have no effect on this type of output.
End of quote.
In other words, when a couple of weeks ago someone said you couldn't add
density to separations because Photoshop would "balance" by subtracting
color elsewhere, it didn't apply across the board. You can with inkjet,
which was the original claim. I seem to recall also that the fellow had
said he "turned the ink all the way up."
Of course, as noted, my laser printer does respond to the changed black
settings. I also note that I found no difference in density range (by
transmission densitometer) between transparency film and plain paper
waxed. The density I'm getting is quite enough for gum, tho not for
others, I suppose. It also occurs to me that the RED layer in printing
all colors together would probably have some actinic effect -- like
pyro.
I'm still beginning, as noted, now trying separation from a slide on a CD,
but am thinking of getting a slide scanner (so I never have to leave
home!) ... about which I shall ask advice in due course.
cheers,
Judy
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