Thanks for the reply Don. I'm using an Isis spectro with Onyx Thrive. My goal is to get the maximum printer gamut on canvas.Ink restrictions were set by reading the Onyx target into the Onyx Thrive. Pre-linearization is done on the printer, the Epson 80600. Ink limits were set by visually inspecting the Onyx target.Delta E is determined by measuring a custom 24 patch target I made and comparing it to the reference values in Colorthink. I agree that I would not want to use an editor. I displayed the ICC profile in Color think and put the 24 patch target up. All the patch points fit into the gamut except the violet patch. The Magenta has the highest Delta E which is 7.35. I'm going to try and increase the ink limits and see if the Delta E's go down. Randy Zaucha
I've used Onyx a lot to make profiles and I agree that setting ink limits has much to do with it. Onyx is a powerful tool but can easily mislead us when we're setting ink limits and restrictions. Glossy canvas in particular has issues due to reflections. I find Onyx profiling to be more like alchemy than science. Recent versions have added some automated simplicity, but I still don't trust it first time around. Let us know how you make out. John Castronovo -----Original Message----- From: zbet66--- via colorsync-users Sent: Monday, June 24, 2019 10:58 PM To: colorsync-users@lists.apple.com Subject: Printer Profiling Issues Thanks for the reply Don. I'm using an Isis spectro with Onyx Thrive. My goal is to get the maximum printer gamut on canvas.Ink restrictions were set by reading the Onyx target into the Onyx Thrive. Pre-linearization is done on the printer, the Epson 80600. Ink limits were set by visually inspecting the Onyx target.Delta E is determined by measuring a custom 24 patch target I made and comparing it to the reference values in Colorthink. I agree that I would not want to use an editor. I displayed the ICC profile in Color think and put the 24 patch target up. All the patch points fit into the gamut except the violet patch. The Magenta has the highest Delta E which is 7.35. I'm going to try and increase the ink limits and see if the Delta E's go down. Randy Zaucha _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/jc%40technicalphoto.... This email sent to jc@technicalphoto.com
Well said Don! Randy, I think there are two different ways of responding to this. One is to talk about how we optimize the pre-profiling calibration steps (ink restrictions, linearization, and total ink limits). Another is to talk about your target and ∆E calculations. Let’s start with this 24 patch "Randy Chart". What is the intent of this procedure? Are you hoping to optimize Pantone color reproduction or something similar? Are you trying to evaluation your calibration and profiling procedures? Artwork reproduction? How were the values created? How are you printing the target? Are you expecting the printed values to match the reference values in the digital file? Are the ∆E values you're generating comparing the reference values to the printed values, or something else? If you make a TIFF file with values like: White L=100 a=0 b=0 Black L=0 a=0 b=0 Red L=60 a=128 b=100 No print will ever hit these values regardless of what rendering intent or profiles we use. And it’s not fair to expect the prints to do it. And their ability to get close to these values isn’t and indication of how good the profile is. White L=100 a=0 b=0 will become whatever the paper white of the media is. Black L=0 a=0 b=0 will become whatever the Dmax of the process is. Red L=60 a=128 b=100 will become roughly whatever the max red saturation is for that process, and the different rendering intents might make it look quite different if things like chroma darkening are employed for example. That said, perhaps all of your patches fall well within the color gamut and you’re printing with AbsolCol and hoping to hit the numbers in the file for colorimetric accuracy as opposed to visual color matching or something else. Either way I think we’d love to hear more about the Randy Chart and the intent for this type of evaluation. Scott Martin www.on-sight.com <http://www.on-sight.com/>
Ink limits were set by visually inspecting the Onyx target.
Can we talk about how we optimize the pre-profiling calibration steps (ink restrictions, linearization, and total ink limits)? RIPs often don’t provide much help here because they don’t give us great tools or analyzing what’s happening so that we can make an educated decision. For initial per channel ink restrictions, some RIPs give us sliders as if to say “Just set them where you want it” while others come up with a suggestion without telling us how they came up with it. A lot of times people like us make an educated guess but are left wondering “Was that the perfect setting? Could it have been better?” When it comes to total ink limits we might test 300, 360 and 400 TIL, for example, and see which looks best. But all are of these approaches appease “good enough” but don’t represent "optimal". The optimal cyan ink restriction might be 76.71% and the optimal TIL might be 342.2%. How do we get to that quickly and easily and stop messing around with glorified guesswork? I’d like to think we can take a data driven approach for scientifically determining the optimal settings for each step in the calibration process. I’ve been geeking out on this for a long time and have created a methodology for this that works with any printing process through any RIP. I call it the ChromaMax calibration methodology and you can read more if you like at https://www.on-sight.com/chromamax/ <https://www.on-sight.com/chromamax/> I also have some blog articles examining the different steps in some detail, like this one: CHROMAMAX PART 1: PRINTER INK RESTRICTIONS https://www.on-sight.com/chromamax-printer-ink-restrictions/ Solvent is a funny beast. If the ink restrictions are too high you’ll have to lower the total ink limits so far it will hurt print quality. If the ink restrictions are too low you will hurt print quality even though you can set the total ink limits really high. There is a see-saw effect here to manage so that you can find that "sweet spot” for optimal over all image quality. So ink restrictions are one part, linearization is another, total ink limiting is another and the final profile is the last. If the three pre-profiling steps are really done right (or what I like to call "optimally”), the final profile won’t have to work as hard and you’ll achieve maximum color gamut, DMax, and have excellent colorimetric color matching like it sounds like you’re looking for. So what I’m suggesting is all these steps are important, not just ink restrictions. Cheers Scott Martin www.on-sight.com <http://www.on-sight.com/>
participants (3)
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John Castronovo
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Scott Martin
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