Digital BW, The Print

Daniel,

linearization in general, means bringing a printer to behave consistently 
across a scale from white to black. In prepress, that would mean that the 50% 
dot should be made up of half ink and half  paper white, and likewise, a 10% 
dot would have 90% paper white etc.

In color managment and profile making, linearization is the first step, before 
profiling: you want a printer to behave well and reproduce each color scale in 
the same consistent way from 100% to paper white. That's a "linear" 
behaviour. You then create and apply a profile "on top" of that.

In the case of OpenPrintmaker (OPM) and InkjetControl (IJC) a printer is 
brought to behave consistently across the grayscale based on a set of 
predefined "Ideal Densities" or "Aims". In that sense, profiling and linearizing 
are wrapped in one.  Because inkjets and their behaviour is closer to 
continuous tone devices than to traditional halftones, the approach to 
linearization is closer to how you would approach darkroom densitometry. 
There are no "dot percents" to talk about (dithers are closer to stochastic 
screens, that's another topic...).

If you have a densitometer and IJC, you are able to read the grayscale target 
that the program generates. Once you read the paper white and the 100% 
black, IJC will give you ("generate") the 24 intermediate densities that your 
scale should match. By using the controls in the program, you can then 
"linearize", or match those densities to your printed output. Once you've done 
that and confirmed it by reading the linearized print of the 26-patch scale and 
comparing to the Aims, you save the settings as a "profile" (or "calibration" or 
whatever you want to call it since it is not an ICC-based profile).  

From this point on, as long as your printer / ink / paper conbination remains 
the same, that profile will be valid and will produce accurate, smooth tonal 
transitions in your images.  In theory, the same profile may work for someone 
else using the exact same combo, but for them it would only be a "canned" 
profile, unless they can edit it (using IJC) to "linearize" their particular output. 

Ultimately, the purpose of linearization is to preserve all those delicate tonal 
transitions in your digital files, and the best way to do it is to have a 
densitometer and check your system before  an important print job. Anything 
else - eyeballed, canned etc will be "decent" enough, but not accurate and 
consistent across systems or over time. Not that much different, really, than a 
meticulous darkroom practitioner who plots characteristic curves for their film 
and paper and matches them up. 


Antonis




--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "danielstaver" 
<daniel@p...> wrote:
> It seems like everybody here knows this already, but I need to ask:
> What is linearization and how is it done? I'm pretty sure it's
> something related to calibration and densitometers, but I've never
> read the exact definition of the process. Apparently I will be
> borrowing a good densitometer next week, so I think this could be
> useful information. I'd be grateful for any clarifying answers. Thanks!