QTR-Quadtone RIP

Don’t use the Relative table. These are perceptual profiles only (in my experience) . . .

Walker


> On Jun 30, 2016, at 12:10 PM, info@moisdelaphoto.ca [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
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> I have question concerning the QTR grey profile relative table.
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> I have created a QTR profile for Museo silver rag on the P800, using the Epson driver. DMax is roughly L*2. Converting from a 2.2 workspace using perceptual rendering creates a perfectly linear toe from L*2 all the way to L*30. However manually targeting the black point to L*2 and converting to the QTR profile using relative rendering produces a strange lagging, source values from L*0 to L*4 are all mapped to L*2 and the visible threshold (L*3) is bumped to source value L*5.  Reading the patches confirms the D Max actually produced is L*2 so I am reluctant to target a higher black value to push the source values L*1-4 out of maximum black.  I am surprised that relative rendering seems to be allowing the CMM to modify ingamut colours by reducing L*3 & 4 to L*2. 
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> Obviously I should be using Perceptual rendering, I‘m just curious to understand this behavior, usually manual black point targeting compresses the luminance scale uniformly, and relative translates the exact values.
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> Thank you
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> Eugene 
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