Re: Linear Tonal Response output (print) ICC profiles possible?
This was an off-list reply, putting it back on-list..
Which, in turn, brings me to suggest that what you _actually_ want is to build a custom profile that uses the actual illuminant of the viewing conditions (ArgyllCMS can do this) coupled with _perceptual_ intent. Do that, and, to the limits of your workflow, the print will visually match the monitor.
I’m not looking for a visual match. That’s what normal ICCs do. What I’m looking for is this: Let’s say we have 18 equidistant values (actual patches in a target) from 0-255 in Photoshop. These would be: 0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 Let’e say our dMax is L* 14.45 on Matte Paper and our dMin (paper white) is L* 96.5 So, Photoshop value of 0 of would be L* of 14.45 and Photoshop value of 255 would be L* of 96.5 What I’m talking about is simple. Is there a consistent way to calibrate with an ICC such that numbers above print like this when measured with a spectro (approximately as the real values have been rounded to 2 decimals): L* 14.45 L* 19.28 L* 24.11 L* 28.94 L* 33.77 L* 38.6 L* 43.43 L* 48.26 L* 53.09 L* 57.92 L* 62.75 L* 67.58 L* 72.41 L* 77.24 L* 82.07 L* 86.9 L* 91.73 L* 96.5 best, Walker
forums@walkerblackwell.com wrote:
What I’m talking about is simple. Is there a consistent way to calibrate with an ICC such that numbers above print like this when measured with a spectro (approximately as the real values have been rounded to 2 decimals):
L* 14.45 L* 19.28 L* 24.11 L* 28.94 L* 33.77 L* 38.6 L* 43.43 L* 48.26 L* 53.09 L* 57.92 L* 62.75 L* 67.58 L* 72.41 L* 77.24 L* 82.07 L* 86.9 L* 91.73 L* 96.5
If you want to define values in L*a*b* in Photoshop, then why not simply do so ? - i.e. create an Lab raster, and enter the pixel values. When printed, these will be translated to the printer device values using the intent you have chosen. i.e. this bypasses the source profile, and uses just the destination (print) profile. [ Also do-able using ArgyllCMS cctiff if your raster is a TIFF L*a*b* space raster - you just need the destination profile to convert to printer space, in contrast to the usual workflow in which you would also need a source profile to interpret the incoming rasters RGB space. ] Absolute Colorimetric intent should then let you reproduce the measured L* values, within the gamut of the printer. Graeme Gill.
Thank you for your thoughtful response Graeme. I will try this. All the best to you! Walker
On Jan 5, 2018, at 7:09 PM, Graeme Gill <graeme2@argyllcms.com> wrote:
forums@walkerblackwell.com wrote:
What I’m talking about is simple. Is there a consistent way to calibrate with an ICC such that numbers above print like this when measured with a spectro (approximately as the real values have been rounded to 2 decimals):
L* 14.45 L* 19.28 L* 24.11 L* 28.94 L* 33.77 L* 38.6 L* 43.43 L* 48.26 L* 53.09 L* 57.92 L* 62.75 L* 67.58 L* 72.41 L* 77.24 L* 82.07 L* 86.9 L* 91.73 L* 96.5
If you want to define values in L*a*b* in Photoshop, then why not simply do so ? - i.e. create an Lab raster, and enter the pixel values. When printed, these will be translated to the printer device values using the intent you have chosen. i.e. this bypasses the source profile, and uses just the destination (print) profile.
[ Also do-able using ArgyllCMS cctiff if your raster is a TIFF L*a*b* space raster - you just need the destination profile to convert to printer space, in contrast to the usual workflow in which you would also need a source profile to interpret the incoming rasters RGB space. ]
Absolute Colorimetric intent should then let you reproduce the measured L* values, within the gamut of the printer.
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