re hp designjet 50ps
re hp designjet 50ps
- Subject: re hp designjet 50ps
- From: Henrik Holmegaard <email@hidden>
- Date: Tue, 27 Nov 2001 09:28:38 +0100
email@hidden wrote:
Is this a "real" 6 color printer ie do you
create a 6 color profile and send 6 components/plates to it from your RIP.
Or is it like the Epson 6 color printers where you can't actually control
the 6 colors individualy and would usually create an RGB profile for it
instead of a CMYK or CcMmYK. Also, I can't find any info on the Heidelberg
RIP that comes with the 50 ps or is it really an hp RIP? Can you send
pre-converted files through the RIP without any further "correction" in the
RIP.
To be suitable as prepress proofers, inkjets should use light cyan
and light magenta. The larger elementary spot size of inkjets
compared to an offset press benefits from building highlights with
light cyan and light magenta. The light cyan and light magenta inks
have a lower optical density than the cyan and magenta inks, so you
are going to be laying down a bit more ink in the highlights.
CcMmYK printing is not like hifi printing, if that is what you mean.
You are looking at four channels and not six. The step from four to
six channels is handled in firmware after the step from three
channels into four channels in Photoshop / Illustrator / InDesign.
Thus CcMmYK printers present a CMYK interface.
CcMmYK printers are fed through two basic types of printing pipeline,
Mac OS QuickDraw / Windows GDI which accepts only three channel RGB
objects in the printing stream, and PostScript which accepts RGB,
CMYK, Grayscale, Lab and custom color spaces in the printing stream.
Thus the number of ink cannisters in the printer is separate from the
number of channels supported in the printing pipeline that feeds the
printer.
To use a CcMmYK printer for prepress proofing, you want to use the
PostScript printing pipeline (which is application level only) and
not the RGB-only OS pipeline. For a CcMmYK printer fed through the
PostScript printing pipeline, you use a CMYK printer target and not
an RGB printer target. Some RIPs will limit ink for you, others will
let you manage the ink limiting manually. Ink limiting should be done
prior to printing the CMYK test chart, just as on a press you run to
optimal density before printing the test chart.
When the test chart is printed, set the profile to 400% total ink. Do
not as on an offset press lower the total ink in the profile and / or
set a high black replacement throughout the inkjet color space. An
inkjet does not require black replacement for color stability, and
black replacement in highlights and midtones (as with GCR set to a
high start) will introduce peppercorn / grain in the screening.
Hope this helps.