Re: Decent results with Gutenprint - the poor man's RIP.
Re: Decent results with Gutenprint - the poor man's RIP.
- Subject: Re: Decent results with Gutenprint - the poor man's RIP.
- From: "Roberto Michelena" <email@hidden>
- Date: Tue, 20 Jun 2006 23:21:32 -0500
In many printers that use light inks, there will also be a separation
applied, to produce (say) the Dark Cyan and Light Cyan raw values from
the input Cyan channel, which can be combined into the linearisation
lookup.
The extent to which some parameters are "canned" and some are tunable
varies a lot among rips. Some I've seen:
- in one end of the spectrum, most proofing rips (as for example EFI
or Oris) have 'canned' light ink separation points. So a 6-color
printer (CMYKLcLm) is linearized as 4-color, the mixing of C and Lc
(and M and Lm) being predetermined and static. You also have no
control over the screening parameters except from specifying
resolution. It's of course also profiled as 4-color.
- as a middle point, ProofMaster (and maybe some other) linearize this
as truly 6-color. The linearization process optimizes not only the
linearity of each of the 6 channels, but the mixing of light inks as
well. Still no control over screening, and profiled as 4-color.
- some RIPs also allow profiling as 6-color. The now defunct Yarc was
one of these.
- in the other end of the Spectrum, in BlackMagic you can not only
linearize per channel and tune the light ink mixing, but also tune the
dot size progression/mixing (for variable dot size printers, as most
modern inkjets are). I believe you profile as 6-color.
- some wide-format RIPs (for example Photoprint) allow you to specify
ink limits not only per channel and global, but also secondary colors
and max CMY. Say you can specify M+Y=160%, M+C=140%, M+K=120%, and so
on. This is quite useful for wide-format solvent inks whose physical
properties can vary a lot from one color mix to another.
I believe BlackMagic's extreme is maybe too much... I wouldn't know
what to do with so many options! unless of course there's some
automatic "dot size mix optimization" method. Well, there could be, I
guess...
But I consider the "individual ink" linearization to be an advantage.
One of the reasons (in my opinion) why linearization tends to be
insufficient to make any two printers match real close, is the
'canned' light ink mixing. If the Cyan max density can vary from
printer to printer, of course the Light Cyan max density can vary too.
And if you don't take that into account and make your mix always with
the same proportions (say 50%C = 60%Lc+ 15%C) you'll get hue shifts
because the light inks are usually a different hue from the dark ones.
-- Roberto Michelena
Infinitek
Lima, Peru
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