## QMS plotmaster colors & pantone colors

### QMS plotmaster colors & pantone colors

[I've xposted this to comp.graphics as some guru there might be able to

Quote:>The problem is : monitor colors != paper colors.

There was a panel devoted to this at SIGGRAPH '90.  Believe me, this problem
exists with probably every computer sold OTC in the world. (Except
MacInTrashes working in on/off bitmap mode with a LaserWriter. 1/2 :-)

Quote:>The solution at the moment is that they have a lot of papers with colors
>on them and find the matching color for the color on screen. they then change
>the colors on screen (using the DPAINT pallet function).

That's a pretty reasonable way to do things considering the level of
technology you own and the bucks the average person has to spend.

Quote:>The colors on screen are wrong then but if you print the picture it looks
>alright. (THIS IS NOT A SOLUTION!)

For what you're doing, it's probably *the* solution, barring writing
a bunch of new code and buying something big to crunch all the numbers.
The linear transformations needed to go from one chunk of colorspace to
another are computationally expensive.  (One of the SIGGRAPH panelists
joked that they didn't see a problem with the linear transformation cost,
they just ran it on their Convex.)  Your other option is to do what I
have done and buy a film recorder.  The colors match up pretty damn
well -- they'd better, since the idea is to take a picture of the
"screen" under controlled settings.

Quote:>My question is, is there some formula to translate screencolor RGB values
>to QMS plotmaster RGB values. If so I can write a program that reads a
>picture calculates the paper-RGB's and prints the picture.

<device-1> RGB != <other-device> RGB, unless you're rather lucky.  If I
display (128,64,64) on my Sun SparcStation w/ Sony monitor, it will *not*
look like (128,64,64) on an Amiga.  It'll be close, granted, but it won't
be the same.  Neither one will look like (128,64,64) on <printer>.

You might want to try printing a series of "test pages" where you print
little blocks of color with the corresponding amiga or QMS RGB values.
Now, you can go back and match up all the little blocks by hand and
look for a function that describes the relationship.  Have fun. :-(

Quote:>Another great option would be to translate PANTONE COLORS (some international
>color numbering system) to RGB values and paper-RGB values

Well, again, you're screwed.  Seiko has a Pantone (tm) certified
Color PostScript printer that you might want to look at.  (We're going
to get one.)  Apparently you can tell it "print Pantone color # x" and it
generates that Pantone color.  The problem is, nobody makes a Pantone
certified monitor (that I'm aware of). fyi, Pantone is a company, not an
ISO standard.  There *are* ISO standards for color mapping, and I'd be
surprised if somebody hasn't written a rough AmigaIFF<->ISO translator.

Hell, just play with the knobs on your monitor, that might fix the problem.
Or turn on/off various lights in the room.  See how complicated the problem
of making screen == paper is?

--

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"If you are the system administrator and this is the first time you are
logging into your system, use the login name root." -- IBM RS/6000 docs

### QMS plotmaster colors & pantone colors

>>The problem is : monitor colors != paper colors.

>There was a panel devoted to this at SIGGRAPH '90.  Believe me, this problem
>exists with probably every computer sold OTC in the world. ...

You might want to look at a paper by Michael G. Lamming and Warren L. Rhodes
in the current ACM Transactions on Graphics (Oct 1990, vol 9, no 4) entitled
"A Simple Method for Improved Color Printing of Monitor Images."

spl (the p stands for
paper?  Who uses
*that*?)
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What is truth and what is fable, where is Ruth and where is Mabel?
- Director/producer John Amiel, heard on NPR

### QMS plotmaster colors & pantone colors

Quote:>>The problem is : monitor colors != paper colors.

Yep. Welcome to Color NonWYSIWYG. Its even worse than that, actually,
monitor colors today != monitor colors tomorrow.
printer colors today != printer colors tomorrow

My current job at radius is writing the software for a little gizmo we
sell that calibrates monitors so that they're consistent from day to day.

Quote:>The linear transformations needed to go from one chunk of colorspace to
>another are computationally expensive.

Inks are *. Most printers work by printing various size dots of Cyan,
Yellow, and Magenta. Cyan removes Red light, Yellow removes Green light, and
Magenta removes Blue light.

In theory.

In practice, CMY aren't independent of each other, so C != (1-R).
Also C+M+Y does not equal black, so printers add a fourth ink, black.
(called K for Key. Black ink is also cheaper.)

Imagine you've got four circles of various sizes and colors that are kind
of transparent. (four glass circles). size the circles until you get the
color you want, remembering that you have to count both the overlapping and
non-overlapping portions. (the color is as seen from 10' away).

That's the simplest possible model.

Now imagine that you have to ask someone else to cut the circles for you.
Imagine that person is deaf, and doesn't quite hear you correctly, so the
circles are sometimes a little bigger or smaller, or not quite circles.

Got a color matched? Good, now feed the paper in crooked and slide all the
yellow circles over 1%.

Quote:>>My question is, is there some formula to translate screencolor RGB values
>>to QMS plotmaster RGB values. If so I can write a program that reads a
>>picture calculates the paper-RGB's and prints the picture.

There's an alogrithm:

convert from your monitors phosphor set to CIE XYZ (a device independent
color space based on human vision).

Print out every possible combination of C,M,Y,K.
Measure output swatches with spectrophotometer to make a XYZ-CMYK
lookup table.

Convert images to XYZ, then lookup CMYK.

Print.

Believe or not, that's about the state of the art (minus details).

Quote:><device-1> RGB != <other-device> RGB, unless you're rather lucky.  If I
>display (128,64,64) on my Sun SparcStation w/ Sony monitor, it will *not*
>look like (128,64,64) on an Amiga.  It'll be close, granted, but it won't
>be the same.  Neither one will look like (128,64,64) on <printer>.

Yeah, but monitor RGB -> XYZ is a 3x3 multiply and some gamma correciton.

Quote:>>Another great option would be to translate PANTONE COLORS (some international
>>color numbering system) to RGB values and paper-RGB values
>Well, again, you're screwed.  Seiko has a Pantone (tm) certified
>Color PostScript printer that you might want to look at.  (We're going
>to get one.)  Apparently you can tell it "print Pantone color # x" and it
>generates that Pantone color.  The problem is, nobody makes a Pantone
>certified monitor (that I'm aware of). fyi, Pantone is a company, not an
>ISO standard.  There *are* ISO standards for color mapping, and I'd be
>surprised if somebody hasn't written a rough AmigaIFF<->ISO translator.

Actually, radius does. Only for the macintosh, though.

There are a lot of Pantone Certified printers, and Pantone has Pantone
colors for the screen (using my toolkit), but you have to be a Pantone

However, Pantone sells a book with CMYK seperations of the Pantone colros
for a SWOP standard (standard set of CMYK inks) that you can buy.

Pierce
--
My postings are my opinions, and my opinions are my own not that of my employer.

(Wha'ja want? Some cute signature file? Hah! I have real work to do.

Hello,

I need to know the interrelationship between Pantone colors.

To bgein with, are PMS colors the same as the CV colors, like used in the
FreeHand 3.1 color picker?

Also, is there any relationship/formula for figuring out PMS/CV Process
colors? (I notice the numbers don't quite correspond...)

This is what happened, BTW; On the logo sheet for a particular company, it
gives a PMS number. I enter this in the CV box in FreeHand. However, the final
output turn purple instead of blue. Any ideas, aside from alignment?

Michael W.

______________________________________________________________________________
Michael Welch                                                     405.447.8149

______"I used to dream and I used to vow...I wouldn't dream of it now"-M______

6. Help !