DELL UP3221Q with iMac Pro

[Oli RSG]

Hello,

I’ve got a new job where they bought me a DELL UP3221Q for color grading jobs. It has an integrated calibration hardware and I am also using a Display Pro.

1. My first issue was the following: the main calibration software from Dell is only available for windows, which means that I can only calibrate using the monitor interface, which has the problem that it doesn’t generate ICC profiles that way. That’s why I am using the Display Pro to profile the screen.
   So first I hardware calibrated the screen (using the monitor controls) to a custom setting of P3 with a gamma of 2.2 and luminance of 140 because I am working in a bright office ( =/ ). Also, I hope that it matches more or less match Mac displays which is what the boss is using to look at the renders. Then I profiled it with Displaycal.
   To do that, I’ve set all settings on the calibration page on “as measured” and clicked on profile only using “single curve + matrix” (because I got a message that some Mac software only supports that kind of profile). I had to chose if I want to embed the calibration curve or not. To my understanding, that shouldn’t make a difference as the calibration curve is linear anyways (” as measured”). I embedded it in any case (should I do this?). I installed the profile and all seems fine.
   Is all this the correct workflow?
2. Then I started working on the display of the iMac. Here I did use calibration for the tone curve and tried putting it on 2.2 or srgb (I’ ve read in the web that iMacs are using a gamma of 2.2 at default, but when I checked the original profile with DisplayCal it had a gamma curve of SRGB – I know the difference is small but interesting anyways). I tried putting the white point on as measured and to put it on 6500.
   Whatever I do, the gamma seems to match, but in comparison the Mac looks magenta and the Dell looks greenish.

I forgot a little bit about the correction profile. For both screens I used the “Spectral LCD PFS Phsophor WLED IPS, 99% P3 (MacBook Pro Retina 2016)” setting. This was probably wrong. The Dell is using this fancy Mini-LED-technology. Which is the right correction for this and which should I use for the iMac? I would really love the get rid of this magenta/green tint.
Another source of error could be of course that the two calibration meters (inbuilt of the dell and the Display Pro) have a slight difference. I hope it wouldn’t be that big though.

I am aware that they will never match completely but I hope to get closer.

I am testing the picture inside the native Mac picture viewer and also in premiere and resolve (both with color management on). All are showing this difference in tint.

[Vincent]

1. To my understanding, that shouldn’t make a difference as the calibration curve is linear anyways (” as measured”). I embedded it in any case (should I do this?). I installed the profile and all seems fine.
   Is all this the correct workflow?

Because you can “profile only” on top of a previous GPU calibration, that is why it asks to choose churrent or linear (no GPU calibration). Calibration (previous one or linear) must be embeded so every time you choose that newly made profile as display profile in OS it will load that GPU calibration. That incluses to remove previous calibration and leave the embeded linear “no calibration” stored in your newly made ICC.
It’s a failsafe to ensure that when loading a HW calibration ICC profile no previous GPU calibration for grey will mess things.

1. Then I started working on the display of the iMac. Here I did use calibration for the tone curve and tried putting it on 2.2 or srgb (I’ ve read in the web that iMacs are using a gamma of 2.2 at default, but when I checked the original profile with DisplayCal it had a gamma curve of SRGB – I know the difference is small but interesting anyways). I tried putting the white point on as measured and to put it on 6500.
   Whatever I do, the gamma seems to match, but in comparison the Mac looks magenta and the Dell looks greenish

Aim for the same white point calibration, and measure instead of appaise.

Dell HW calibration software (old DUCCS or new one that looks to be Calman based) was not known for its white accuracy. It takes too many simplifications that current Dell HW Qc cannot give, like for example (old DUCCS) assumes that WP won’t drift with brightness OSD setting and such.

I forgot a little bit about the correction profile. For both screens I used the “Spectral LCD PFS Phsophor WLED IPS, 99% P3 (MacBook Pro Retina 2016)” setting. This was probably wrong. The Dell is using this fancy Mini-LED-technology. Which is the right correction for this and which should I use for the iMac? I would really love the get rid of this magenta/green tint.

P3 mac should ouse the one you have.

For Dell take a look on colorimeter correction database. Likely to be a WLED PFS but in AdobeRGB+P3 flavor instead of just P3 like macs. Its WLED PFS HP Z24x correction in DisplayCAL.

Another source of error could be of course that the two calibration meters (inbuilt of the dell and the Display Pro) have a slight difference. I hope it wouldn’t be that big though.

I am aware that they will never match completely but I hope to get closer.

I am testing the picture inside the native Mac picture viewer and also in premiere and resolve (both with color management on). All are showing this difference in tint.

Dell has an SDK to manually upload calibrations but for newer versions (including the onde recoomended for your model) it has lost such feature.

Jumped in the wrong boat… “non real HDR” CG319X seems the sensible choice with such high budget.

Also check color uniformity in the region patch where built it colorimeter shows up. Display cal report \ uniformity report 5×5. Then on resulting HTML report change default combo box (deltaE: color+brigtness error in one number) to deltaC (just color).

[Vincent]

White point may be corrected with a GPU calibration, but maybe Apple desktop color management engine does not like it.

[Vincent]

“Likely to be a WLED PFS but in AdobeRGB+P3 flavor instead of just P3 like macs. Its WLED PFS HP Z24x correction in DisplayCAL.”

Or a cheap QLED like Benq SW2700PT. Both should habe near full AdobeRGB + P3 coverage. There was a SW2700PT native gamut CCSS somewhere in this forum, in colorimeter database correction some of them may not be measured in native gamut, have to check it.

[Vincent]

It seems not!

Color Gamut (typical): CIE1931 Adobe RGB 93%, CIE1976 DCI-P3 99.8%, CIE1976 BT2020 83%

https://www.delltechnologies.com/asset/en-us/products/electronics-and-accessories/technical-support/dell-ultrasharp-32-hdr-premiercolor-monitor-up3221q-data-sheet.pdf

It should be the same backlight as or close to Mac P3 screen. Another reason to do not buy it.

Anyway to be sure rent or borrow an spectrophotometer and measure Dell monitor backlight.

Another option to correction white point with a GPU calibration in DisplayCAl is to pay a Calman license and use its PFS correction with your i1d3 colorimeter (maybe with some custom correction instead).

• This reply was modified 2 years, 9 months ago by Vincent.
• This reply was modified 2 years, 9 months ago by Vincent.
• This reply was modified 2 years, 9 months ago by Vincent.

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[Oli RSG]

Hello,

first of all: Thanks a lot! Your answers helped me understand the whole thing better.

I wasn’t really included in the monitor choice decision. The company has deals with vendors and apparently it had to be a dell screen. Honestly, as we only deliver rec709 and 99% for the web, this screen is more than enough. All I asked for anyways was a screen with hardware calibration.
I don’t know much about screen technology but I don’t think it has the same backlight as the Mac because the Dell uses 2000 Minileds instead of a regular backlight like the Macs.

I did try out the the correction for the Z24x and the results where almost identical according to the verification document. The only notable difference was that with the Mac correction, the ” Measured vs. assumed target whitepoint ΔE*00 ” was above delta 2, while with the Z24x correction the value was good.

Also the Mac is showing a similarly big deviation above delta 2. What could one the source of this problem? The profile whitepoint is at 6581 and it measured 6284.

Also what’s confusing me, is that to my eyes, the Mac display seems magenta in the shadows. But according to the verification the Mac is about +5% too blue in the shadows and -5% to -10% red, while green is +2%. I am a bit confused because my eyes tell me it should be about +5% blue and +5% red (at least in comparison with the dell who’s RGB gray balance is impressive according to the verification. Except for one red value that is at 5%, everything all the values have only around 2% deviation.

“You can do verification measurements to assess the display chain’s (display profile – video card and the calibration curves in its gamma table – monitor) fit to the measured data, or to find out about the soft proofing capabilities of the display chain.”

Or maybe I understand the verification wrong.

or… I should just not trust my eyes to much….

I attached three verification reports:

1. Mac
2. Dell with Mac correction
3. Dell with z24x correction

I am confused about the white values.

Attachments:

You must be logged in to view attached files.

[Vincent]

I don’t know much about screen technology but I don’t think it has the same backlight as the Mac because the Dell uses 2000 Minileds instead of a regular backlight like the Macs.

No, that way reasoning is wrong. Mini led is about how many of them, not about the “spectral power dsitribution” (SPD) of each led, which can be the same.

LED SPD going though panel is what gives you certain color primaries. If SPD is equal or very close, colorimeter should use the same correction.

I did try out the the correction for the Z24x and the results where almost identical according to the verification document. The only notable difference was that with the Mac correction, the ” Measured vs. assumed target whitepoint ΔE*00 ” was above delta 2, while with the Z24x correction the value was good.

Actual correction must be measured with an spectrophotometer, but given specs, just measure where is native gamut green: AdobeRGB green or P3 green?
1st one=> close to HP Z24x (and poor internal colorimeter or poor software or color uniformity mismatch between center & integrated colorimeter placing)
2nd one=> Mac P3
if is is sligthy desaturated from P3, it may use WLED PFS 95% P3 used on some multimedia gaming monitors (panasonic VVX correction)
But you need to measure with an spectro to be 100% sure.

Also the Mac is showing a similarly big deviation above delta 2. What could one the source of this problem? The profile whitepoint is at 6581 and it measured 6284.

Attach report as HTML, with PDF I cannot see details. It can be that macbook whitepiont drifts with brightness settings (expected) or other user misconfiguration. I cannot see it with a PDF.

Also what’s confusing me, is that to my eyes, the Mac display seems magenta in the shadows. But according to the verification the Mac is about +5% too blue in the shadows and -5% to -10% red, while green is +2%. I am a bit confused because my eyes tell me it should be about +5% blue and +5% red (at least in comparison with the dell who’s RGB gray balance is impressive according to the verification. Except for one red value that is at 5%, everything all the values have only around 2% deviation.

Do not look RGB balance, look at a*b* axis in greys, it’s easier.
Looks like overall greys have a slight green cast but near black goes to normal. Also macbook GPU can cause banding if not AMD-like with dithering and such.

 

I am confused about the white values.

Easy, explained above => if there is no review showing spectral power distribution of the LED, you are guessing correction. Rent or borrow an i1Pro2, make sure you use it in high res mode (3nm) because using default mode (i1profiler) and such it cannot measure WLED pFS properly.

Or try to guess better by green native gamut primary, its location on CIE xy compared to AdobeRGB’s or P3’s green.

• This reply was modified 2 years, 9 months ago by Vincent.
• This reply was modified 2 years, 9 months ago by Vincent.

[Oli RSG]

Hello,

again thanks a lot for the clarifying answer.

According to my tests (hardware calibrated to p3) it has 98,5% P3 coverage. So it cannot be the WLED PFS 95% P3, right? I don’t have access to a spectrometer and have to keep some deadlines, so I cannot really go that road atm. I am really curious though which backlight technology is actually used.

Or try to guess better by green native gamut primary, its location on CIE xy compared to AdobeRGB’s or P3’s green.

I don’t really understand this part.

I will attach the html files now. Can it be read out of there?

Attachments:

You must be logged in to view attached files.

[Vincent]

I don’t really understand this part.

HW calibrate to Native gamut or AdobeRGB. Then compare 255 green (report checkbox=absolute, combo=xyY or XYZ coord) to AdobeRGB green.

If it is very close then it is not mac “P3only ” WLED PFS and it is not “WLED PFS 95%” like gamer displays or some TVs, it would be like HP Z24x G2 (and Dell specs will be wrong)

BTW, Dell HW cal is working fin efor that P3 calibration in grey.

Regarding atachments:

-mac TRC should not be sRGB, leave defaults, desktop is color managed
-do not use fast calibrating unless dispay grey was on spot
-unique grey levels are low, check calibration curves on profile info. Look on upper right corner to see how much whote point correction it is in calibration if any. If 255input=255 output, macpro whitepoint is as bad as report shows (bad factory cal, or cal that varies too much with brightness setting, or… some software white like “Night mode”? ) and you’ll have to correct it in GPU if OS does not cause much trouble,
If there was a huge WP corection in calibration curves redo calibration because something was wrong.

• This reply was modified 2 years, 8 months ago by Vincent.

[Oli RSG]

Thank you so much!

I have True Tone and automatic brightness adjustments off of course. But I did change the brightness in between. I didn’t expect that to be a possible source for such different white values.

I will work on your propositions when I find a bit of time to figure out the green value of the Dell.

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