monitor profile rendering intent

[Lundberg02]

Googling, I found this     http://forum.luminous-landscape.com/index.php?topic=39015.0;wap2    in which was this quote:

"But... in practice it doesn't make any difference if an application translates perceptual or colormetric to the monitor profile.
TRC matrix based profiles do not contain a table for perceptual RI and even LUT based monitor profiles do not contain a perceptual table (AFAIK).
As the profiles do not contain any information about perceptual RI and common CMM's don't do their own translations here the RI to a monitor profile is de facto always colormetric.
You'll see a difference with the above mentioned test profile (as it contains the respective tables) but you won't see a difference with a monitor profile.
You can verify that for instance in Capture One (Pro) where you can set the RI in the preferences.
You are absolutely correct about matrix based profiles.
But I don't agree with you about LUT based profiles. All LUT based monitor profiles that I have seen (e.g. created with basICColor display4, ColorEyes Display Pro, i1Match,  ProfileMaker, MonacoPROFILER etc) have perceptual and colorimetric LUT tags. I have not examined them closely but at least the LUT based profile created with basICColor display software has different perceptual and colorimetric LUTs."


There was no date, but references to FireFox 3.5 indicate it was a long time ago.  Does anyone have more up to date info on which apps and calibrations are perceptual now. What about factory monitor cal profiles? I'm particularly convened about opening a RAW fiie as ProPhoto 16bit and viewing it on a Dell U2413 wide gamut factory profile. What am I seeing perceptual or clipped?

[digitaldog]

I don't know the answer to your question but assuming the LUT profile has more than one table, how would we select which RI is used or toggle between them? I know of no way to do so. The display profile is selected by ICC aware app's no question. Past that, I don't know of how one would pick which RI to use or even know what RI is used. So it seems a tad moot.

[Lundberg02]

I generally use ACR to view RAW as a ProPhoto tif. it struck me that I don't know what I'm seeing. If I do a test print using PS manages colors and select perceptual from the Epson choices, I get a print that matches the screen pretty well and I am using the Dell factory cal for my U2413. The cal sheet they sent with it has excellent delta e. I have seen comments hat say you can't believe the factory data. Without some sort of elaborate test equipment, I don't know how I could verify that their profile does perceptual. I did a test of the ProPhoto Printer Test Image , doing all four rendering intents, from PS. Perceptual looked like the screen but the best looking print was Absolute. Go figure.  I don't know of any way to find out what my monitor renders.
Some clown in another forum says that i1 creates selectable profiles but I haven't seen anything in their manual, procedure, or user experience that even mentions it, neither does any other color management tool. It took me six months to get an answer from Dell about their ridiculous statement  in the read me for the Dell UltraSharp Color Calibration Solution that "some Macs may have an unrecoverable crash requiring a second monitor to reboot" (answer: only OS 10.6 and 10.7), so I don't think I'll go that route again. Bruce Wright at X-Rite will at least respond promptly so I think Ill ask him.

[digitaldog]

Some clown in another forum says that i1 creates selectable profiles but I haven't seen anything in their manual, procedure, or user experience that even mentions it, neither does any other color management tool.

Without full context, perhaps he's referring to the preferred RI that most such profiles contain which set what is used when the user has no direct access to select the RI? For printer profiles that's usually Perceptual.
I see no way to set this in i1Profiler.

[Lundberg02]

I would certainly hope that the preferred RI would be perceptual. I wonder how many reasonably proficient Photoshop users don't know what they're actually seeing when they do what I do, view RAW as ProPhoto on a wide gamut monitor. I really don't know what rendering intent I'm seeing, but my perceptual prints look quite similar. I have asked X-Rite about intents, but don't expect an answer until maybe Wednesday. I have the Coke machine philosophy, kick it until it comes out. Too long in the military or around it, I suppose.

[digitaldog]

It's pretty easy to see what the preferred RI is with a profile, on a Mac, using the ColorSync Utility:

And again, it's moot IF you have an application that gives you the option of what RI to select.

[Lundberg02]

yeah, cool, I have actually done that but forgot about it. Will check my profiles

[Lundberg02]

Here's what I got back from Bruce Wright. He did not clarify what happens when you do  a LUT cal with the Dell Color Calibration Solution using the i1 Display Pro.

<

Comment:


When you create a monitor profile with i1Profiler software, you will be creating a profile that contains all three rendering intents. We would recommend you choose Perceptual for viewing photographic images.  >

[digitaldog]

Here's what I got back from Bruce Wright.

Comment:

When you create a monitor profile with i1Profiler software, you will be creating a profile that contains all three rendering intents. We would recommend you choose Perceptual for viewing photographic images.  >

Choose how?

[Lundberg02]

Good question. If I ever get around to using my i1 Display Pro, I should be able to see or not see how to do it.  Im waiting for a guy in another forum to tell me how he made out calibrating the Dell U2413 LUT using the DCCS, but it's been almost a month and nada.
 I have yet to see anywhere in a forum or on the net any positive or negative result of doing this, and I still can't see how putting 256 points into table to represent 16,382 points that were already there gets you anywhere.  My factory profile's data sheet has very low delta Es, and gives good screen match, so I'm reluctant to do either the monitor profile or the LUT cal without someone's actual experience. The Photography Life forum has an article that purports to tell you exactly "how to properly calibrate the U2413 etc etc" but that is a split infinitive, and the forum owner constantly tells everyone in the comments that they should use Windows 10 bit and buy an Eizo, so the whole thing is a non sequitur. When I ask what is the point of calibrating 16,382 points with 256, he goes nuts.

[D Fosse]

and I still can't see how putting 256 points into table to represent 16,382 points that were already there gets you anywhere.

That's the whole point of hardware calibration, where you access the monitor's internal high-bit LUT instead of the 8-bit video card pipeline (as with the i1 Profiler software).

If you have an i1D3 sensor, and you can download the Dell calibration software for free, it's a no-brainer. It will definitely be an improvement over the "factory cal" which I would take with a bucket of salt. Factory calibrated to what, exactly? Even assuming it's accurate - how do they know what white point and contrast range works best for you?

EDIT: When you say you "won't go that route again" re Dell color calibration solution, does that mean you won't use it, or don't ask them about it? Because this software does hardware calibration in high bit depth, and as such is vastly preferable over i1Profiler.

[Lundberg02]

Not going that route again    means trying to use Dell Tech support, although now i have a name contact and can avoid the six month runaround.
Please explain how the 256 data points you can get on a Mac using the DCCS and the i1 Display Pro can adequately determine a 14 bit curve.
I have never seen this addressed, nor have I ever seen any comment anywhere from a user who actually tried the DCCS.
I have seen comments that factory profiles are no good, but Dell provides a cal data sheet with each U2413, are these fiction? The monitor looks good, prints match well, and ColorSync shows a large gamut, larger than aRGB. A small part of aRGB is missing, hence the claim 98%, but the gamut volume of the  monitor is considerably larger than aRGB.

[D Fosse]

Yes, the unit receives an 8 bit signal from the Mac, and outputs the same 8 to the panel. You don't ever get higher precision than that, even with the Dell factory settings and using the factory profile. You'll always have 256 discrete steps per channel, that's a hard limit whatever the method (unless you have a full 10-bit path, which rarely works as advertised even on Windows).

But since the Dell software communicates directly with the onboard graphics processor in the monitor, operating in 14 bit depth, there are no rounding errors in recalculating those 8 bits to correct for the display. The 8 bits that hit the panel will always be evenly spaced with no banding. That's what the high bit internal LUT does.

[Lundberg02]

I'm not sure by what I/O the Dell sw would communicate directly, could you clarify that?

Yes, I have have read that the Win 10 bit has problems, particularly that if you set it up some of your apps don't work. Even so, it is unfortunate that you can't use the DCCS with a WIN virtual machine because there has to be a physical USB.

With 40 years experience transitioning design to production, I'm well aware of the tricks the factory uses to get hardware out of the house. Test til it passes, uncalibrated test equipment which is always mysteriously biased toward acceptance, testing in  the wrong order, misreading the print, and so on.  Still, you would think that Dell values their reputation for adequate consumer gear and would not provide a fake cal sheet. I'll have to dig mine out and post it here.
i wonder if the DCCS version for Mac only sends 8 bit/channel images to the Mac for display or somehow using the mystery I/O you referenced it sends 10 bit which the monitor then displays as 8bit+FRC. I'd really like to see a flow diagram. Anyway the least significant 4 bits of the LUT are probably linear interpolation, the next two up are from FRC if the DCCS puts them there, so what do you really have?  Also I sonde if the Windows version actually expects a 10 bit flow?
The so called expert in Photography Life who wants everyone to use Windows and buy an Eizo has alsosaid you can't calibrate the U2413 because it is a GB-LED. The DCCs and i1 Display Pro are explicitly set up for just that so it is not a problem. Dell is definitely not that stupid.

[D Fosse]

I'm not sure by what I/O the Dell sw would communicate directly, could you clarify that?

Well, that's what the separate USB cable is for. This doesn't go through the DP/DVI signal path.

I don't think Dell is stupid at all. They're just very aggressively pushing the "paper spec:price" ratio because they know that's where people will go. And they're good at it. Just looking at the data sheet, a U2413 is absolutely identical to an Eizo CX241 or an NEC PA242 - and yet it sells at less than half the price. The inevitable conclusion that I draw from that is they're cutting corners somewhere. The trick is to figure out exactly where that happens (and a factory calibration is an obvious candidate), and then decide whether it will impact your needs. It may, or it may not.

Anyway, the 10-bit capability in the panel is moot unless it receives a 10-bit signal, which it doesn't on Mac and rarely on Windows. So the additional two FRC bits aren't used.

If you get a good match from screen to print using the factory settings, that's fine. But if you set the white and black points manually, you might be able to get an even better match.

One obvious shortcut they could make, is to set the white point along the Kelvin scale, measuring only the blue/yellow component. So they get low delta E's here, but what about the green/magenta axis? Do they measure that?

[Lundberg02]

Good comments, as always I have to google like a maniac to keep up with the people here. I managed to find some user experience with the U2413 and calibration, but haven't been able to give it more than a cursory look which seemed to indicate people have a lot of problems. I'll summarize it a bit later today. Also will post the U2413 data sheet.

[Lundberg02]

Dell factory cal sheet attached. No mention of white point, so you have to assume they used the nominal.

[digitaldog]

I'd still like to know how a user is supposed to pick and use a RI with a display profile according to X-rite.

[Lundberg02]

i'll be finding that out at some point I suppose. Might have to ask  Bruce Wright if I haven't worn out my welcome.

[Lundberg02]

I have asked Bruce to clarify how to select rendering after doing a LUT cal.
As far as user experience, many of the dozen or so reports I was able to find were based on much older versions of the DCCS, and I haven't sorted them out yet. The latest version 1.5.3 allows use of the i1Pro, and i1Pro 2 in addition to the i1Display Pro. It also produces reports.