DesignJet profiling ABC (1)
DesignJet profiling ABC (1)
- Subject: DesignJet profiling ABC (1)
- From: Henrik Holmegaard <email@hidden>
- Date: Wed, 28 Nov 2001 18:29:38 +0100
Yes that helps enormously. I was confused by the 6 color thing.
Well, if you found it useful, then lets look at some PostScript RIP basics.
Printer manufacturers market their printers as 6 color devices.
For smoother screening if CcMmYK.
There was also quite
a bit of talk a while back about profiling Epson inkjets as RGB devices.
If there is no PostScript RIP, you don't have a choice except to use
the OS printing pipeline even if your application supports a CMYK
color model. With the HP printers, there are PostScript RIPs. As long
as I can remember, this list has had two groups, the QuickDraw folks
and the PostScript folks. I never understood the QuickDraw folks -:).
Or is that wrong to profile an Epson as an RGB device.
Many Epson users don't have PostScript RIPs and can't send CMYK data
to the printer. For them the only option is to use an RGB test chart.
For instance, if QuarkXPress or Photoshop which both support CMYK
must hand a CMYK object to the QuickDraw printing pipeline, that
object must be converted to RGB before the OS pipeline can receive it
... whether or not the conversion is color managed. You can maybe get
this to work for loose images with some twisting and turning, but not
for page proofs.
If the printer is fed data from a PostScript RIP, whether the RIP
resides on a print server as software or is built into the printer's
hardware controller, then you need to profile as CMYK. You will not
optimally fingerprint the color space of a PostScript Level 1, Level
2 or Level 3 printer if you profile from an RGB target. A CMYK or
CcMmYK RIP can't print RGB data, so the PostScript Level 1 device RGB
to device CMYK conversion will be applied, also called the Level 1
conversion though in fact it applies equally whether the RIP is Level
1, Level 2 or Level 3. This conversion uses two customizable
parameters for black generation which means your RGB test chart shows
the result of an in-RIP black generation. The deviceCMYK mode used
when you send a CMYK test chart gives your profile a better
fingerprint of the dark end of the color space because a RIP does not
apply its customized black generation to a deviceCMYK object (except
if in-RIP emulation for CMYK objects is enabled, see below). The
on-line iQueue manual has a little more about the ins and outs of the
PSL1 / PSL2 / PSL3 device color rendering procedure for RGB to CMYK.
Why would you profile them differently?
Because there is a PostScript RIP involved, see above.
(End part 1)