January 2020 - colorsync-users

RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

I hate to say this but you won't get to the bottom of this until you compared them side by side. If you have the time, pack one of your Dell and drive up to Montréal. I have good coffee 😊 / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Wire ~ via colorsync-users Sent: Tuesday, January 7, 2020 8:38 PM To: 'colorsync-users?lists.apple.com' List <colorsync-users(a)lists.apple.com> Subject: Re: perceptual differences in Lab deltaE The NEC is probably a 3% better display than the Dell at 4x the price

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RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

Hi Simon, Interesting observations. Your findings corroborates my very own, humble experience. If I understood you correctly, you and your students found that our color vision is "less forgiving" of color differences in neutral colors and "more forgiving" in saturated colors? I agree intuitively that observing color side by side does not "forgive" much 😊 I'm curious how were you able to print chart patches with as little as 0.3 deltaE (which flavor?) color differences... Suppose I was to replicate your findings with my students? Best / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of simon--- via colorsync-users Sent: Tuesday, January 7, 2020 5:48 AM To: Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> Subject: perceptual differences in Lab deltaE Hi Andrew, I did some tests a few years ago by printing charts patches to exhibit small deltaE variations. My conclusion at the time was that the limit of deltaE of ≤ 1 was fine for colours with values of a or b > ±10 but as the colour approached the neutral (L) axis in the range 40 ≤ L ≤ 70 smaller values of deltaE were clearly visible. Most of my test subjects could detect differences of about 0.3 when the patches were compared side-by-side, and (almost a neutral grey). My conclusion from this was not surprising - for all my test subjects the Lab space was not perfectly perceptually uniform, and detecting differences in deltaE was significantly easier for values of -3 ≤ (a or b) ≤ 3 when comparing patches side-by-side. Simon simon(a)richstitch.com

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RE: 1 billion colors
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

Wire, I'm not really after one "best" visualization. MacAdam ellipses are daunting to me, I won't go there unless I have to. I realize no color space will ever have perfect qualities but that's not what I'm after... My point, in raising the question with Steve yesterday, was what kind of numerical abstraction can be applied to distinguish between "unique" colors -- sorry to sound like a broken record in the context of color management? I confess, initially, I had this 16.7 million RGB "color combinations" question in mind. But, like many here, I am aware of research that concluded that men and women with "normal color vision" can only discriminate 10 million different colors (or something like that?) which is referred as the "Gamut of real colors", I think, see Dr Michael Pointer -- a nice guy, btw 😉 I never read the papers about this concept (I have no idea how that number was ever arrived at or very vaguely) but I took it "on faith" that this estimate made intuitive sense to me. There are only 24 hours in a day. / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Wire ~ via colorsync-users Sent: Wednesday, January 8, 2020 8:39 AM To: 'colorsync-users?lists.apple.com' List <colorsync-users(a)lists.apple.com> Subject: Re: 1 billion colors On Tue, Jan 7, 2020 at 14:21 Steve Upton via colorsync-users < colorsync-users(a)lists.apple.com> wrote: > > > > On Jan 7, 2020, at 1:36 PM, Roger Breton via colorsync-users < > colorsync-users(a)lists.apple.com> wrote: > > > > So, Steve, anything that is outside of that "1 Lab" unique cube is > considered a "different color", in ColorThink? Is that your criteria? > > effectively, yes. > > Though if you "do the math", it becomes clear that 1 Lab cubes don't > pack properly so that the centers of each cube are 1 dE apart from all > the other centers, *and* that you can't really do that because > sphere's don't pack efficiently, etc, etc, etc > > Steve > Roger, it seems you are thinking about something like packing of MacAdam ellipses... https://en.m.wikipedia.org/wiki/MacAdam_ellipse The MacAdams ellipse describes relative capacity to distinguish color across regions of the locus. Normal individual observers — normal meaning those who you would not define as color-blind — will have varying abilities to discriminate depending on the color. (Is it fair to use the term color in this way? If color is a pure qualia can you have color blindness? How can one be blind to that which for him does not exist? ;) The idea is you pick a coordinate and ask how well an individual, as compared to the population, is able to discriminate difference surrounding this coordinate? And how sensitive is the population to differences across the gamut (word police: "we have you surrounded"). The MacAdam idea leads to a heap or camel or Zeno's paradox: Pick a point and draw a MacAdam ellipse. Within the ellipse, color is considered indistinguishable. Between the neighboring ellipses, color is distinguishable. Pick a point half-way between neighboring ellipses and draw another MacAdam ellipse. Where did the color go?! This may leads me to consider I want an encoding system with a resolution much finer than one standard color difference. Say if I had a system of millions of "colors" nee qualia (oh, wait, strike that, reverse it... Er no wait... waaaahhhg!) and I want a stimulus system that driven by a numerical non-uniformly perceptually distributed integer RGB values to avoid visible quantization artifacts, I may find I want the data format to encode a couple orders of magnitude more stimulus than qualia to ensure I cover the corner cases. Therefore "billions of colors." QED Seeing this MacAdam idea really affected my visualization of the distortions inherent to the XY plot. And cemented my view that Adobe RGB was singled-minded in desire to cover press, with newer DCI being a much more balanced extension of sRGB. As somewhat related aside, DisplayCal has gamut projections in a mode called DIN99, which looks to me like it might be intended to be a very perceptually weighted plot. There's not much about it returned by web search... I admit I haven't asked at the obvious place, over at the DCal forum. I'll post the Dell gamut vs standard gamuts as DIN99 so others can see. _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx(a)videotron.ca

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RE: 1 billion colors
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

So, Steve, anything that is outside of that "1 Lab" unique cube is considered a "different color", in ColorThink? Is that your criteria? / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Steve Upton via colorsync-users Sent: Tuesday, January 7, 2020 3:59 PM To: colorsync-users(a)lists.apple.com Subject: Re: 1 billion colors > On Jan 6, 2020, at 1:36 PM, Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> wrote: > > Well, Andrew, just to push the discussion further, I would *love* to hear what Steve Upton would have to say about “unique colors” since he’s the one that wrote the application: what numerical criteria does Steve use in ColorThink to distinguish among “unique colors”? > Gah! I've been drawn into the angels-on-the-head-of-a-pin discussion again! I agree with all of you... does that help? I have to admit the "There's a color missing, prove me wrong" is pretty damn funny. Good to get a chuckle from this stuff sometimes. My 2 bits? There's an interesting point here about the difference between addressable colors and addressable unique colors. For me (not necessarily using the correct terms) an addressable color in this discussion would be any RGB value that results in a Yxy value that falls within the chromaticity diagram and represents an actual, visible color. This includes any precision level so imaginary 128bit-per-channel RGB spaces would be included as well. There'd be a lot of wasted bits addressing imperceptible color differences but they'd be real colors. This brings me to: Addressable *unique* colors is the idea that perceptual spaces like Lab have a kind of maximum resolution, where we could use a set of coordinates that is no more precise than our ability to see the differences between colors. Each unique color is effectively assigned a coordinate and we're good to go. "But wait", you might say, "color perception is analogue and infinitely variable" (nod to Mr Gnaegy, good to hear from you sir). "A hard-edged coordinate system could never capture it!" I agree that we're analogue beasties but it's not a problem. In our discussion we're talking about trying to address unique colors. If we use such a hard-edged coordinate system there's nothing saying it can't be slid around / re-aligned with infinite precision, only that the differences between the coordinates would need to remain the minimum perceptible difference between colors - therefore it still addresses unique colors... If I understand and slightly warp the intentions of our color forefathers properly, CIELAB was intended to be just such a coordinate system, where 1 unit of movement in any direction would be the human perceptual limit of color change. If you added up the "volume" of such 1-unit cubes in a defined area, such as a printer gamut, then you'd have a number representing the number of unique colors available. That's exactly what I do in ColorThink. Unfortunately CIELAB is flawed, or perhaps it's better to say that human color perception doesn't adhere to such a simple model. Newer models have been created such as CIECAM that help address some of these limitations. Suffice to say that there's broad agreement that CIELAB and delta-E 76 are dangerous to use naively, yet remain quite useful and delta-E 2000 helps bring color differencing numbers more in line with human perception. Though I recognized that the concept of a total gamut volume is disputable and somewhat flawed from the start, I thought that it probably still had value and chose to include it in ColorThink Pro. At the very least I thought it would start some interesting discussions! Overall, I think it has been useful, especially in a comparative sense. Are there better ways of doing it? Undoubtedly. Is there agreement on which ways are better? Not much that I can find yet, but work on the science continues and we continue to learn as we go. Those who are attending the Color20 Conference in San Diego next week will be treated to a sneak peak of what's coming in ColorThink 4 later this year - like new color spaces for graphing, advanced gamut comparison functions, and so forth. regards, Steve _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx(a)videotron.ca

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Re: perceptual differences in Lab deltaE
by Wire ~ 08 Jan '20

08 Jan '20

The Dell only has room for 2 user cal presets On Tue, Jan 7, 2020 at 17:28 Wire ~ <wire(a)lexiphanicism.com> wrote: > The Dell only has room for 2 user cal presets > > On Tue, Jan 7, 2020 at 17:20 Roger Breton via colorsync-users < > colorsync-users(a)lists.apple.com> wrote: > >> I concur, and I wonder to what extent these 14-bit LUTs are >> "programmable"? >> I hate to ask the question but it's a feature I always took for granted? >> On >> the Dell specs Wire gave the link to, they talk about LUTs that are >> "loaded", see towards the middle of the page, they refer to LUTs as >> "Precalculated sets of values". >> I confess I'm confused. I don't know enough about monitor calibration to >> say >> for sure and I don't want to speculate. >> >> https://www.displayspecifications.com/en/model/da704af >> >> Thanks / Roger >> >> -----Original Message----- >> From: colorsync-users >> <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of >> Andrew Rodney via colorsync-users >> Sent: Tuesday, January 7, 2020 8:11 PM >> To: Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> >> Subject: Re: perceptual differences in Lab deltaE >> >> >> >> > On Jan 7, 2020, at 5:56 PM, Roger Breton via colorsync-users >> <colorsync-users(a)lists.apple.com> wrote: >> > >> > I guess the same can be asked of the NECs and the Eizo's? >> >> Both are with their software products (IOW, SpectraView for NEC). The >> SpectraView Engine has an autocorrecting sensor that corrects the color >> and >> brightness of the backlight in real time. The monitor is equipped with a >> programmable 3DLUT, there are up to 10 programmable presets or roll your >> own. >> >> Andrew Rodney >> http://www.digitaldog.net/ <http://www.digitaldog.net/> >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> colorsync-users mailing list (colorsync-users(a)lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> >> https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca >> >> This email sent to graxx(a)videotron.ca >> >> _______________________________________________ >> Do not post admin requests to the list. They will be ignored. >> colorsync-users mailing list (colorsync-users(a)lists.apple.com) >> Help/Unsubscribe/Update your Subscription: >> >> https://lists.apple.com/mailman/options/colorsync-users/wire%40lexiphanicis… >> >> This email sent to wire(a)lexiphanicism.com >> >

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RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

I concur, and I wonder to what extent these 14-bit LUTs are "programmable"? I hate to ask the question but it's a feature I always took for granted? On the Dell specs Wire gave the link to, they talk about LUTs that are "loaded", see towards the middle of the page, they refer to LUTs as "Precalculated sets of values". I confess I'm confused. I don't know enough about monitor calibration to say for sure and I don't want to speculate. https://www.displayspecifications.com/en/model/da704af Thanks / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Andrew Rodney via colorsync-users Sent: Tuesday, January 7, 2020 8:11 PM To: Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> Subject: Re: perceptual differences in Lab deltaE > On Jan 7, 2020, at 5:56 PM, Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> wrote: > > I guess the same can be asked of the NECs and the Eizo's? Both are with their software products (IOW, SpectraView for NEC). The SpectraView Engine has an autocorrecting sensor that corrects the color and brightness of the backlight in real time. The monitor is equipped with a programmable 3DLUT, there are up to 10 programmable presets or roll your own. Andrew Rodney http://www.digitaldog.net/ <http://www.digitaldog.net/> _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/graxx%40videotron.ca This email sent to graxx(a)videotron.ca

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RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

Wire, My next question is whether those 14-bit LUTs are programmable in any way? Is the Dell version of i1Profiler able to access that part of the monitor's memory during calibration? Are DispCal/Argyll able to access that part of the monitor's memory during calibration? Or is it proprietary? I guess the same can be asked of the NECs and the Eizo's? I confess my ignorance in this matter but it is a fascinating part of these monitor's technologies. Sorry for the model display number in my earlier reply... / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Wire ~ via colorsync-users Sent: Tuesday, January 7, 2020 7:20 PM To: 'colorsync-users?lists.apple.com' List <colorsync-users(a)lists.apple.com> Subject: Re: perceptual differences in Lab deltaE Roger, the UP2516D interfaces are indeed 10 bit with a 14-bit internal LUT. So back to interest in Dell's cal and 3rd party support. Eat that NEC. https://www.displayspecifications.com/en/model/da704af Appears ArgyllCMS has long supported 10-bit graphics. Modern OS will drive it as such, but I'm connecting via DVI-D to HDMI which is limited to 8 bpc. This old NVidia has HDMI and DP so there's a possibility that I can swap to DisplayPort and get 10 bits. Seems unneeded as 8 looks smooth, but a bit here, a bit there, pretty soon you're talking real bits. /wire

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RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

Yes, Andrew, you posted this image a while ago and all I can say is it's 'buttery smooth' on my PA271W with the 10-bit option activated in both my NVIDIA 1070 graphic cards and Photoshop's GPU Performance > Advanced setup. / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Andrew Rodney via colorsync-users Sent: Tuesday, January 7, 2020 7:34 PM To: 'colorsync-users?lists.apple.com' List <colorsync-users(a)lists.apple.com> Subject: Re: perceptual differences in Lab deltaE Roger, as you may be aware, that other guy may not; the bit depth of the panel is simply one attribute to a fully high bit display path. Yes, it's important. But the video card, the OS, the application and the panel all have to be high bit for a true high bit path. Photoshop and Lightroom support high bit video, later Mac OSs do as well (late to the party but there's support). Then there's the video card that may or may not be high bit. If not, there's going to be a high bit to 8-bit conversion which isn't ideal. How one hooks up the display affects this too. Best way to check, view this image, in Photoshop, at 100% zoom, should be utterly smooth: https://www.dropbox.com/s/s14f4w7dq85r7oo/10-bit-test-ramp.zip?dl=0 <https://www.dropbox.com/s/s14f4w7dq85r7oo/10-bit-test-ramp.zip?dl=0> As for a silly comment: "Eat that NEC", there's far, far more to a great color reference smart display system than the bit depth. We can go there if so desired. All bits are real. Not all comments about them are <g>. Andrew Rodney http://www.digitaldog.net/ <http://www.digitaldog.net/>

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RE: perceptual differences in Lab deltaE
by graxx＠videotron.ca 08 Jan '20

08 Jan '20

Andrew, I'll start "humble", I'm only interested at this point to tell what type of "information reduction" is at play between pixel values in a file and measured pixel values on screen. For sure, we all *know* it's not a 1:1 relationship. Like, this is crazy, but I confess I never stopped to think what happens in Photoshop when working in 16bit modes? Suppose my video card can only honor 8-bits: can you imagine the huge "reduction" going behind the scene between the image in the file and the image on screen? Now what happens in the case of a 10-bit video card scenario? Assuming a 10-bit capable display like your 271Q and my 271W, and Wire's UP2916? Surely the reduction must not never be as severe. But I'd like to know, quantitatively, what kind of "compression" are we talking about. For now, I'm only interested in looking at R=G=B values, that will give plenty of data to graph to play with. But I don't think I'll expand this to the whole 16.7 million (let alone 1.04 billion) colors. / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Andrew Rodney via colorsync-users Sent: Tuesday, January 7, 2020 3:25 PM To: Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> Subject: Re: perceptual differences in Lab deltaE So if (ugh that be hard) you're going to use your 16 million color test file, what's going to happen if it's in Adobe RGB vs. sRGB vs. ProPhoto RGB vs. the gamut and calibration of your display? Andrew Rodney http://www.digitaldog.net/ <http://www.digitaldog.net/> > On Jan 7, 2020, at 1:21 PM, Roger Breton via colorsync-users <colorsync-users(a)lists.apple.com> wrote: > > Ilah, > > Glad you brought this up because that's exactly one my current "pet > projects". My code is not finished yet but basically, I'm going to be > sweeping the entire "1024" scale with my instrument, to determine, > exactly, what is what. I'll be glad to report as soon as I'm done -- can't wait! > > / Roger

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RE: Humans (and cameras and scanners) do not have a color gamut (?)
by graxx＠videotron.ca 07 Jan '20

07 Jan '20

Henry, I'm not a digital camera designer but what don't you understand about the fact that a camera is a sophisticated "light detection system"? It's pretty much a color measuring instrument (others could correct me) but an i1pro does not have a "gamut" per se or a filter-based colorimeter, they take light in and spit out numbers in response -- same with digital cameras, they take light in and spit out sets of RGB numbers. Surely there's a lot of math going on inside the CPU of a Nikon or a Canon or a SONY camera, like estimation of scene illuminant by which tonal responses are likely adjusted. There may very well be some kind of "model" of various 'natural scenes' because, just like during the creation of output profiles, it helps to have some kind of "assumptions" as to what ranges of colors or luminances are to be expected. But is that a"gamut" per se? A gamut is a physical construct, it comes from something measurable that have "limits". I hope that helps... / Roger -----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca(a)lists.apple.com> On Behalf Of Henry Davis via colorsync-users Sent: Tuesday, January 7, 2020 4:45 PM To: colorsync-users(a)lists.apple.com Subject: Re: Humans (and cameras and scanners) do not have a color gamut (?) When the “cameras absolutely do not have gamuts” quote moves from “some response” of a camera to “color accuracy” I get lost. It sounds as though there is a ruler(the display) measuring a non-dimensional entity for accuracy. The quote seems to assume that the camera has infinite perfection but it’s up to some mysterious other entity to prove that it doesn’t have infinite perfection. I’m now losing my fight to understand - I was pretty much following the previous threads about the distinction between color and numbers but this curve ball has me swinging and missing. I believe the quote was supposed to bring some clarity but it didn’t work for me. Maybe there’s another way to explain not having a gamut that will help. Henry Davis

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