QTR-Quadtone RIP

I don't know the answer for certain, but my gut feeling is that your idea will work.

I've played around a bunch with the QTR tools, and written some code that does similar functions. Fundamentally, the tools are generating curves from pairs of data: an input (an expected value) and an output (a measured value). You can look at this as a series of X,Y points. QTR probably uses some form of spline algorithm (see <http://en.wikipedia.org/wiki/Spline_(mathematics)>) to interpolate the full curves using those points. Different algorithms have different requirements: some need a certain number of points, some need to have the points spaced at equidistant intervals. I don't know which algorithm QTR uses.

Given that the QTR tools don't seem to need any configuration to indicate the particular patches (they're just read from the CGATS file, as you know), I'd reckon that there's no assumption being made as to the specific intervals between patches. Hence, having arbitrary patches as you're describing will probably work.

--John


On 7 Jun 2012, at 3:36 AM, Ernst Dinkla wrote:

> On 06/04/2012 03:45 PM, Ernst Dinkla wrote:
>> Is it necessary to have steps of 5% or 2% in the targets to let them
>> function in the QTR linearisation and profiling tools? In other words;
>> would a 33 or 34 step target with 3% increase and one 4% or 1% step
>> compromise the algorithms of the tools?
> 
> No reply yet. Could be a stupid question and do not hesitate to rub that 
> in then, I have written stupid questions before.
> 
> Let me explain why I wrote that question. I am looking for a compromise 
> between the 21 and 51 step greyscale targets. The last can create issues 
> when either the basic tone range of the printed target is too irregular 
> and/or the density measurements are not increasing properly. The 21 step 
> does it well on those aspects but if I create RGB curves with Photoshop 
> etc the curve control points are close to the 21 number and I think that 
> the linearity etc could be improved by a curve based on a higher, odd 
> target number to take out interference between the two data sets.
> To create an accurate, regular 8-bit target there is no other sensible 
> choice than identical steps of 20+1 or 50+1 so 5%K or 2%K steps. I can 
> make a 16-bit (15-bit+1 actually) target with 35+1 steps and am already 
> halfway that work but if there is a bottleneck on 16 bit in either Color 
> Port, Measure Tool, QTR-Create-ICC-RGB tool's linearisation, the 
> application color management in printing, then that work is idle. 
> Whether the driver in the end delivers 8-bit data to the printer is of 
> less concern to me but up to that point I would like to have 16-bit 
> processing. 16-bit driver would be nice too but is not available in all 
> cases, some rounding off at that stage does not worry me.
> 
> 
> -- 
> Met vriendelijke groet, Ernst
> 
> Dinkla Grafische Techniek
> Quad, piëzografie, giclée
> www.pigment-print.com
> 
> 
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