CYMK and monitor colours?

CYMK and monitor colours?

Post by John Smit » Thu, 09 Apr 1998 04:00:00



Hello,

...Sorry if this question seems a bit stupid, I mainly do Web design and so
far, everything I have printed, I have used my Epson 800(mostly to good
effect-with no major colour miss-match)..
However, I have designed some leaflets that needs to be printed
professionally.
I have been told to convert my image to CYMK...when I do this any colours
that were red turn to a murky orange on the screen...and when I use Pantone
Process colours there does not seem to be any bright red.
Is it that my monitor needs calibrating or is it something that I am doing
wrong...I have read a few books but I am a little confused.

Thanx for any advice.

 
 
 

CYMK and monitor colours?

Post by PFig » Thu, 09 Apr 1998 04:00:00


<<..Sorry if this question seems a bit stupid, I mainly do Web design and so
far, everything I have printed, I have used my Epson 800(mostly to good
effect-with no major colour miss-match)..
However, I have designed some leaflets that needs to be printed
professionally.
I have been told to convert my image to CYMK...when I do this any colours
that were red turn to a murky orange on the screen...and when I use Pantone
Process colours there does not seem to be any bright red.
Is it that my monitor needs calibrating or is it something that I am doing
wrong...I have read a few books but I am a little confused.>>

You are trying to display CMYK values on an RGB device and to do that somewhat
accurately in Photoshop, you need a couple of  things.

First you have to calibrate the monitor, preferably to the D50 (5000 deg.
Kelvin) standard. You can most easily achieve this with hardware calibration,
but barring that, you can get by with the Gamma Control Panel, a file that has
been printed out and perhaps the Ole No Moire file from your Photoshop CD. Read
the section on monitor calibration in your manual and follow the steps
carefully.

Secondly, you need to set up the Printing Inks and Separation Setup properly
for the type of printing you are doing. If you are printing a brochure on a
sheetfed press on premium paper, you can probably choose SWOP Coated inkset and
20% Dot Gain in your Printing Inks Setup. The settings here affect both how
your RGB file is converted to CMYK and how Photoshop displays CMYK images.

Next, before you convert to CMYK, you need to open your Separation Setup and
change the defaults. They are not very good for most kinds of reproduction.
Choose GCR with a Light black generation plate. Set the Black Ink Limit to
85%-90% and then set the Total Ink Limit to whatever the press suggests,
usually 280-300% Total Ink for web presses and 300-340% Total Ink for
sheetfeds.

Getting back to your monitor. In Monitor Setup, if you don't have a Colorsync
profile to load into this (and you probably wouldn't unless you had a hardware
calibrator and accompaning software), then choose a Monitor Profile that most
closely matches the type of monitor you are using. For example, if you have any
sort of a Trinitron tube, then pick one the Trinitron profiles. Also while in
this dialogue box set the Gamma to 1.8, the color temperature to 5000 and the
Ambient Light to High. Setting the Ambient light to either Medium or Low will
cause Photoshop to add a slight gamma tweak to your conversions. Better to view
your monitor in an almost dark room and get used to reading the Info Pallete.

Before converting RGB files is the perfect time to sweep the cursor and read
the numbers in the Info Pallete. You will be able to read the values for color
shifts. If you have a known neutral area, you know that all three colors should
be close to the same values. You can set the info pallete to read RGB on one
half and CMYK on the other. That way it will tell you what the CMYK values will
be after you convert. I usually am working already in CMYK and have one side
set at Actual Color and the other at Total Ink. (Maybe in 5.0 we will have all
three at once)

It's not uncommon for certain colors to lose saturation and hue when converted
from RGB to CMYK. The CMYK gamut (range) is far more restricted than RGB. Ink
on paper simply cannot match that of light emitted from your monitor. Blues are
especially hard to reproduce because of the relative impurity of the Cyan ink
most presses use.

I would strongly suggest buying Real World Photoshop 4 on Peachpit Press and
Makeready by Dan Margulis on MIS Press for extensive information regarding
printing and Photoshop.

Peter Figen