Graphics Programs Reference
In-Depth Information
is CMYK. However, the print driver plays a much larger role than the
inks, pigments, dyes, or other process that actually creates the color.
Most desktop printers use a driver to send the data to the desktop
printer. By and large, these are either
Quickdraw
drivers found on the
Macintosh or
GDI
drivers found on the PC. Both types of drivers do not
understand how to utilize CMYK data, only RGB. When a user sends an
RGB file through one of these drivers to their printer, a conversion to the
native color space of the printer happens on-the-fly by this print driver.
The “black box” processor in these drivers actually expects RGB data so
that a very special and proprietary conversion can take place. When you
send that Epson 2200 an RGB file, a CcMmYKk conversion takes place.
The RGB data has to be separated correctly into the seven color compo-
nents for this printer. If, however, a user were to send CMYK data to this
printer and driver, the “black box” in the driver has to convert the data
back to RGB in order to produce the CcMmYKk conversion necessary.
This conversion from CMYK back to RGB and then to CcMmYKk often
produces heinous color prints. You can try this for yourself.
The moral of this story is you can't assume that you should be pro-
filing a printer for CMYK just because the material it ultimately uses to
make colors is some mix of CMYK inks. In fact, very few printers are true
RGB devices. We saw in Chapter 1 that in order to make a print, we need
to deal with subtractive color. RGB would indicate that we are making
color with light. Most printers that we would assume are RGB devices
are really CMYK devices since we are dealing with subtractive color.
There are a few true RGB printers like the LightJet, Lambda, Fuji Fron-
tier, and Pictrography line. They actually expose light sensitive media
using lasers or light valves.
Some printers will accept only CMYK data. A four-color printing press
will not accept RGB data. It is possible to find software or hardware con-
trolling the press that may accept RGB data and convert that into CMYK.
CMYK is nonetheless necessary for output to a printing press. If we wish
to profile our output devices, we need to know what color model the
printer and drivers will accept. It will be necessary to send target files in
the appropriate color model through these devices in order to provide
something we can measure to build an ICC profile. A device that accepts
RGB data will need a target file in this color model to be sent to the print
driver for output and measuring. A device that accepts CMYK data will
need a different target file for this process.
Building Profiles—An Overview
Building printer profiles, in theory, is not all that different from the
process used to build other device profiles. The products that build printer
profiles supply target files that we output and then measure. These target
files contain a specific number of colored patches that have a numeri-
cally known value. After being printed, an instrument, usually a Spec-
