QTR-Quadtone RIP

Sorry my previous post was unclear.

I have read the previous discussions on this board on linearization using QTR to build curves. I have tried different ink limit, boost, gray_highlight and gray_shadow values with 21, 33, and 50 gray targets and not archived satisfactory results.

Phil wrote:

>> I suggest you use the 21 x4 chart... 
>> measuring 256 is not going to get you a smoother curve. 
>> The random 21x4 works well...this is what Roy suggested...

I think Roy's suggestion applies to linearizing curves using QTR to do the linearization. I've given up on that and an trying to linearize outside of QTR by editing the .quad curve files directly. This is not a new idea and I think it must work. 

To use John Cone's inks you use his .quad files with QTR as a RIP only and not a curve builder. Cone's .quad files were not built with QTR. (Look at any of his curves with QTR curve view and that's immediately apparent). I haven't tried Cone's inks but unless many people are deluding themselves they give good results and validate the results. Unfortunately, Cone's methods are anything but open source so I'm trying to do what he does without knowing how he does it. 

I am thinking of the .quad files as specifying how Lab L values correspond to density by controlling the amounts of ink. The .quad files contain a 16-bit number for each of 256 levels for each ink. I would love if Roy or anyone else would jump in here an clarify this for me. The getting started file in the CurveDesign folder of the current Mac distribution mentions a Curve-Info file but I can's find it so I'm guessing here.

I'm trying to build a black only profile so there is only on ink and, therefor, only one number is determining how dark each level prints. In theory, I should be able to adjust it to get a truly linear curve. 

By editing the 16-bit numbers one should be able to change each level. I am hoping to do so more systematically than by trial and error.

Off to print two more 256 gray targets to measure to separate the actual nonlinearities in the .quad curve from the variations of paper, printer, and measurement.

Thank you,

Vincent


Vincent Wan
August 2012 PhD. Committee on the Conceptual and Historical Studies of Science, University of Chicago.		
Once and future professor of Biology