RE: define linearization
RE: define linearization
- Subject: RE: define linearization
- From: "Bruce J. Lindbloom" <email@hidden>
- Date: Sat, 17 Aug 2002 09:53:26 -0500
Greg Staler wrote:
>
Anyone care to describe the linearize process further - specifically what
>
the process involves, and what purpose it serves?
Ray Maxwell replied:
>
When this procedure is applied to proofers it usually means that you are
>
adjusting the device (using software and measuring instruments) to some
>
known stable condition. With most inkjets this means setting single channel
>
ink limits, calibrating the tone reproduction to have some standard dot gain
>
(TVI), and setting the total ink limits. The dot gain might be set to some
>
standard like SWOP (approx. 20%). It does not mean that the device in
>
linear in most cases. Usually the output at 50% would be 70% or 20% dot
>
gain or TVI (Tonal Value Increase).
That was a _great_ reply.
Shooting off on a tangent, I would add that it is probably not a good idea
to strictly linearize a proofer because that maps the 256 digital tone
levels into linear reflectances. A reflectance scale does not have a uniform
tone distribution to the eye. Strict linearization is to proofers like gamma
1.0 is to monitors (both are linear energy scales). "Dot gain" on a proofer
has the same benefit that gamma 2.2 has on a monitor, namely that it tends
to spread your 256 available levels out more uniformly to the eye. So it is
probably better to "linearize" to a standard that has some dot gain (i.e. a
non-linear standard).
In addition to keeping your proofer in a known, stable state, linearization
can redistribute your 256 tones into a more useful range. It is not unusual
to see a proofer whose scale starts out fine from 0%, 1%, ... 60%, but from
60 to 100% the same tone is printed. So 40% of your 256 available tones are
wasted. Linearization can redistribute these tones (e.g. stretch the scale)
so that this waste is removed (or at least reduced).
--
Bruce J. Lindbloom
email@hidden
http://www.brucelindbloom.com
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