Attn: Graeme Gill regarding lineraization
Attn: Graeme Gill regarding lineraization
- Subject: Attn: Graeme Gill regarding lineraization
- From: "Mark Rice" <email@hidden>
- Date: Wed, 6 Jun 2007 15:53:48 -0400
Hi Graeme - I saw you mention of the Colorbus rip and how it linearizes. I
used the Colorbus RIP many years ago and was happy with it.
I presently have a Mutoh Toucan printer with Onyx RIP, and I am very
unhappy. I used to work with photographic devices such as the Durst Lambda
and the LVT film recorder. The rips used to drive those used "iterative
linearization". The has a set of target density aim points, and it would
compare the delta e of the read in grayscales to the aim points, and make
and adjustment toward the aim point from the presently read grayscale until
all the outputs were nearly exactly on the aim point targets.
I believe the Colorbus worked in a similar fashion - generating iterative
linearization, and the ICC profiles were applied after linearization - am I
correct?
With Onyx, and many other RIPS I have used for Inkjet printers, a
linearization is generated from a buried mathematical curve, apparently
generated from what one specifies as the ink restrictions as a base point
for the curve. The curve cannot be altered or even predicted. When one
generates a linearization, and it is close but not dead on, re-linearizing
may make it better, or it may make it worse, since the previous
linearization does not exist in the computer's algorithm.
Anyway, my linearizations are extremely inexact compared to the photographic
images I used to output. Can you think of any solutions for this problem? I
talked to the head colorscientist at Onyx, and he acted as if I were being
ridiculously picky.
Thanks,
Mark Rice
Some linearisation systems work that way - they linearise the device to some
target determined from the particular device behaviour. Others have fixed
targets for a particular device+media, and therefore do line up multiple
instances of the same device+media to the same "state"
(the one I wrote for the Colorbus Cyclone worked in the latter way, making
it suitable for proofing).
Graeme Gill.
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