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Author Topic: Epson SureColor P800  (Read 22182 times)

digitaldog

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Re: Epson SureColor P800
« Reply #100 on: September 23, 2017, 10:28:41 am »

It's true but what's allowed varies with the RI.
Again, I can't understand how an ICC profile knows anything about image content. They don't even 'know' anything about an adjacent pixel do they? IOW, they examine a pixel value alone and convert it based on a number of assumptions perhaps and a lot of data is a guess (by the time the output profile comes into the scene, the data is usually in Lab, the source color space is unknown). IF an image is what I understand it to be, I still can't understand how a profile knows anything about it to alter a conversion based on content. Confused..... >:( 

WE humans need to view pixels in context and view what really IS an image and decide what RI to use based on those pixels and color in context no? That's why we toggle the RI's and select the one we visually prefer. We humans that wish to control this mapping have to use a full color managed path which includes soft proofing and control over the rendering intent if we desire this kind of control. Going full circle as to why Printer Manages Color is a black box approach with less control for the image creator and/or print maker.
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Doug Gray

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Re: Epson SureColor P800
« Reply #101 on: September 23, 2017, 12:55:42 pm »

Again, I can't understand how an ICC profile knows anything about image content. They don't even 'know' anything about an adjacent pixel do they? IOW, they examine a pixel value alone and convert it based on a number of assumptions perhaps and a lot of data is a guess (by the time the output profile comes into the scene, the data is usually in Lab, the source color space is unknown). IF an image is what I understand it to be, I still can't understand how a profile knows anything about it to alter a conversion based on content. Confused..... >:( 

Perhaps my words were unclear. ICC profiles are only for image independent color mapping. This means each pixel's transformation is independent of the pixels in the rest of the image. Your understanding is correct, a point I had noted earlier. It's just that you use different words similar to the above and I used "image independent" which is academic, mathematical terminology, and is the way I refer to things by default.  They have the same meaning.

From a prior post of mine:
ICC profiles in any RI can only do image independent gamut mapping


I also agree with this:
Quote
WE humans need to view pixels in context and view what really IS an image and decide what RI to use based on those pixels and color in context no? That's why we toggle the RI's and select the one we visually prefer. We humans that wish to control this mapping have to use a full color managed path which includes soft proofing and control over the rendering intent if we desire this kind of control. Going full circle as to why Printer Manages Color is a black box approach with less control for the image creator and/or print maker.
« Last Edit: September 23, 2017, 01:24:45 pm by Doug Gray »
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digitaldog

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Re: Epson SureColor P800
« Reply #102 on: September 24, 2017, 10:34:52 am »

Perhaps my words were unclear. ICC profiles are only for image independent color mapping.
What was unclear to me was this text: Gamut mapping, that is not image dependent...
That implies to me there is gamut mapping that is image dependent. Just caught my here.
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Doug Gray

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Re: Epson SureColor P800
« Reply #103 on: September 24, 2017, 07:00:14 pm »

What was unclear to me was this text: Gamut mapping, that is not image dependent...
That implies to me there is gamut mapping that is image dependent. Just caught my here.

Gamut mapping that is image dependent is believed to potentially offer better visual results than image independent gamut mapping. Here's a paper that explores it:

https://www.researchgate.net/publication/5918124_Image-Dependent_Gamut_Mapping_as_Optimization_Problem

My specification that Perceptual Intent did not use image dependent gamut mapping was just to emphasize the point as some may confuse that with Perceptual Intent not being Colorimetric.  Of course all ICC profile usage is image independent. That is, a pixel color conversion is unrelated to the values of other pixels. As far as I am aware, all Printer Manages Color is also image independent and hence could be described, or duplicated, in the perceptual intent tables of ICC profiles and so could be soft proofed against. But printer manufacturers apparently choose not to do so. Perhaps the reason is financial. If consumers like the "pop" of printer manages providing a proofing profile would also allow duplication on other manufacturer's printers. Secret sauce becomes less secret.
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