Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla 
<E.Dinkla@c...> wrote:
> Target is CMYK, 8 rows of patches, 33 patches per row = 264. 
> The GRAD file next to it has 8 lists that say C,LC. M, LM etc. 
> It will print the target with Colorbase. The split to the 8 
> channels will be based on the CMK percentages in the target, Y 
> isn't split.
> 
> an excerpt from the Colorsync list:
> 
> Well, a simple look at the reference data lets me draw the 
> conclusion that
> this is more a linearisation tool than a calibration tool.
> 
> The patches in there look like cyan, magenta, yellow and grey 
> patches.
> Just not enough colors to build a lookup-table.
> 
> Rolf
> 


Yes it absolutely is CMYK, and needs to be printed from the 
application, just like doing the same thing for any RIP. Pushing it 
through the RGB driver would simply muck up the process.

And yes what it is doing is setting the linearity for that printer, 
the same thing that Epson does at the factory, and the same thing 
that HP does for the DJ130 (and others) on the printer. HP calls it 
calibration, most RIPs call it linearization (and clipping). Clipping 
limits the inks at the point where density no longer increases (very 
general). In the RIP I use, the linearization process builds a LUT 
between what is asked for, and what is printed. Remember a LUT is 
simply a table of input values to output amounts to achieve that 
value. It doesn't have to be a 3D matrix like a profile, because you 
are only dealing with one color channel at a time.

I don't see how changing the size would effect the measured values if 
you do it the way Ernst has suggested. For the i1 spectro, you need 
at least 8mm high by 8mm wide patches. Wider patches let you scan at 
a higher speed (more reads per second). You might also be able to 
remake the targets using Coloport and the ref. files, but since I 
don't own one of these printers, I can't check it. Cropping the un-
needed borders, or resampling the image is probably the best way.