QTR-Quadtone RIP

Roy,

Related to Keith’s mentioned use of QTR-Linearize-Quad and Dig-negs:  PiezoDN utilizes QTR-Linearize-Quad. The .quads themselves are built (differently than normal Piezo print quads) to enable calibration of the printed negative from the darkroom print using QTR-Linearize-Quad and 129 error-corrected measurements from light to dark.

We utilize a similar thing (with a different error correction formula) in Piezography Professional Edition. Basically we’ve applied our algorithm for fixing measurement errors (either in brush-strokes from hand-coated prints or flicker in spectros) prior to QTR-Linearize-Quad in order to properly calibrate Piezography with minimal errors and high bit-depth and smoothness. This error correction algo. for PPE is the algorithm that we’ve used for a decade + to profile Piezo .quads (at 256 steps). I recently updated it a bit for our building of Pro curves as well . . .

best,
Walker

> On Dec 9, 2016, at 3:55 PM, Roy Harrington roy@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> 
> Hi Keith
> 
> I'm a little confused about your comments regarding QTR-Linearize-Data vs QTR-Linearize-Quad.
> The Linearize-Data script has been around a long time and its mainly to analyze measurement data files to extract
> the L-values needed for the LINEARIZE capability in Profile Creation program.  
> I added dealing with Digital Negatives a while ago by adding the reverse order output from Linearize--Data
> and changing the LINEARIZE function to accept reverse order data.  (this is the only way because QTRgui is unmodifable)
> LINEARIZE is different for negs because the correction is opposite.
> 
> Later than the above I added a Linearize-Quad script that analyzes measurement data like above but just immediately
> applies this to an existing .quad file.  (mostly this is useful for Piezo .quad's that don't go thru Profile Create)
> The Linearize-Quad was not part of the digital negative linearizing since that's in Profile Create.
> So I don't get the "I use QTR-Linearize-Quad frequently with PiezoDN" comment.
> 
> --
> Lastly -- yes you can use both GRAY_CURVE and LINEARIZE be used in the same QTR Curve.
> 
> Roy
> 
> On Thu, Dec 8, 2016 at 10:30 PM, Keith Schreiber keith@... <mailto:keith@...> [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com <mailto:QuadtoneRIP@yahoogroups.com>> wrote:
> 
> 
> Hi folks,
> 
> I just tried using QTR-Linearize-Data for the first time and found that for linearizing digital negatives it works, but not quite as Roy described it here, unless I misunderstood something. I read the part quoted below to mean the input data in the text file for digital negs should be from black to white. 
> 
> QTR-Linearize-Data will not take numbers from black to white; whether Den or LAB, it gives the error message "The Lab values are not in order. Cannot be linearized." 
> 
> However, when a text file with numbers from white to black is dropped onto QTR-Linearize-Data, it produces both a standard white to black LINEARIZE= string, AND an inverted one, black to white, for digital negatives.
> 
> LINEARIZE="88.18 83.49 75.44 69.33 66.12 63.64 61.83 60.05 57.75 55.53 51.78 48.73 45.82 42.59 38.68 34.25 30.54 27.43 24.22 22.41 20.68"
> 
> For Digital Negative:
> LINEARIZE="20.68 22.41 24.22 27.43 30.54 34.25 38.68 42.59 45.82 48.73 51.78 55.53 57.75 60.05 61.83 63.64 66.12 69.33 75.44 83.49 88.18"
> 
> 
> This may not be news to anyone but me, but I thought I should mention it just in case. I've never used QTR-Linearize-Data before, though I use QTR-Linearize-Quad frequently with PiezoDN.
> 
> One question though: Can both GRAY_CURVE and LINEARIZE be used in the same QTR Curve? I know at least one person who does that with digital negatives, and successfully I think, but I've never seen it discussed or written about anywhere.
> 
> Cheers,
> Keith
> 
> Keith Schreiber
> jkschreiber.com <http://jkschreiber.com/>
> 
> 
>> On Sep 13, 2016, at 11:02 PM, Roy Harrington roy@... <mailto:roy@...> [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com <mailto:QuadtoneRIP@yahoogroups.com>> wrote:
>> 
>> For ordinary printing the
>> values must be from White to Black, but for digital negatives use Black to White.
>> LINEARIZE will create a correction curve such that the new curve set will produce
>> a step with linear Lab values -- i.e. it linearizes for Lab values.
> 
> 
> 
> 
> 
> 
> -- 
> Roy Harrington
> roy@... <mailto:roy@...>
> www.harrington.com <http://www.harrington.com/>
> 
>