Eizo CS2420: Meaning of Validation Reports in Different Gamuts

Hello All,

 

I've hardware-calibrated an Eizo CS2420 with ColorNavigator and i1Display Pro. I've attached reports from (i) Native-gamut and (ii) AdobeRGB gamut target calibrations.

 

As you will see, the AdobeRGB report is much better than the Native report, in both dE2000 and dEab values. The Native report measures a max dEab of 8+.

 

(1) Would someone explain the Native-gamut report to me, please? -Why is there (such) a difference between the Native and AdobeRGB reports, particularly in dEab values?

 

(2) Could this be down to a problem with my i1Display? (Support from Eizo has suggested Red is not being correctly measured by the colorimeter; at the moment i'm unable to get another colorimeter to check this.)

 

I've done a number of hardware-calibrations in Native gamut over the last 10 days with different colour-temperature and brightness settings -the reports have been consistent in the values measured. Any insight would be appeciated.

 

 

With thanks,

:)

Native gamut, as the name implies is the full gamut the display is capable of producing. It may be wider than Adobe RGB (1998) in some areas of color space, less in others. There are several ways to define gamut volume which may be OT. Adobe RGB gamut is just that. Your display doesn't natively produce this but you can calibrate to that aim point. Now the high dE is an issue and not normal so I suspect you should contact Eizo. A dE of 8 isn't good.

The dE values are calculated based on the reference values (what the numbers should be) and what they are indeed and not tied to gamut per se. It's just that when you ask for one target, the dE is much higher and as I said, 8 isn't good at all so something sounds off. This may help in terms of dE:

 

Delta-E and color accuracy

In this 7 minute video I'll cover: What is Delta-E and how we use it to evaluate color differences. Color Accuracy: what it really means, how we measure it using ColorThink Pro and BableColor CT&A. This is an edited subset of a video covering RGB working spaces from raw data (sRGB urban legend Part 1).

Low Rez:

High Rez: http://digitaldog.net/files/Delta-E and Color Accuracy Video.mp4

Hello DD,

 

In respect to gamut and dE2000, i get it (in fact many of ur other posts are how i have learned about it :)

 

I wondered why Native gamut would show values which were cause for concern, while ARGB gamut would show excellent values? -I thought they would be equally as good (or equally as bad).

 

I have been in contact with Eizo, they agreed the numbers were 'odd'. After sending the reports to Japan, they advised my colorimeter may be the problem -i'll get another to compare as soon as i can.

 

Also, thanks for confirming the dEab is an issue. -dEab is not a measurment i've come across before (dE2000 and deltaC is what i understand), and i wanted confirmation that the values here should be addressed.

 

Regards.

The idea it is the colorimeter is somewhat sound, depending on make/model (filters can age). It's a bit odd that you wouldn't get large errors no matter the target for calibration but I agree that it would be useful to attempt testing with a different unit, hopefully one you can borrow to confirm.

Don't take such reports too seriously when the dE values are kind of low (say below 2-4), but when larger differences show up as you've seen, then it's a good idea to drill down what might be going on.

For whatever reason, I can't view a zoomed up preview of your reports so I can't go over them carefully. What you want to be looking for is good old deltaE (and some formula), is that what is reported as 8?

No idea what -dEab is. The superb BableColor PDF help file provides this as differing 'variations':

 

FORMULA SELECTION

 

Fourteen DeltaE formulas and variants are available:

 

• ∆E*ab
  "CIELAB color-difference", referenced to the selected space or deck illuminant (shown only if same illuminant for both sides)
   
   
  
• ∆E*uv
  "CIELUV color-difference", referenced to the selected space or deck illuminant (shown only if same illuminant for both sides)
   
   
  
• ∆E*ab D50
  "CIELAB color-difference", referenced to D50 illuminant
   
   
  
• ∆E*uv D50
  "CIELUV color-difference", referenced to D50 illuminant
   
   
  
• ∆E*94
  ∆E*94-textile
  "CIE94 color-difference", referenced to the selected space or deck illuminant (shown only if same illuminant for both sides). The ∆E*94-textile version has its kL factor equal to 2; kL equals one for the standard version.
   
   
  
• ∆E*94 D50
  ∆E*94-textile D50
  "CIE94 color-difference", referenced to D50 illuminant
   
   
  
• ∆E*CMC(2:1)∆E*CMC(1:1)
   
  "CMC:)c) color-difference", referenced to the selected space or deck illuminant (shown only if same illuminant for both sides). CMC(2:1) is used for acceptability (pass/fail) measurements while CMC(1:1) is used for perceptibility measurements.
   
   
  
• ∆E*CMC(2:1) D50
  ∆E*CMC(1:1) D50
  "CMC:)c) color-difference", referenced to D50 illuminant
   
   
  
• ∆E00
  "CIEDE2000 color-difference", referenced to the selected space or deck illuminant (shown only if same illuminant for both sides).
   
   
  
• ∆E00 D50
  "CIEDE2000 color-difference", referenced to D50 illuminant
  

I can't figure out why the editor here is placing smiling faces in the pasted text above. That text should show up as C:1 (C : 1).

Edited October 10, 2018 by digitaldog

(There may be a problem with the site today, i couldn't view the reports fullsize when i posted them without them scrollong endlessly in a loop.)

 

Ah so, this is the thing -i thought there was only one dE of importance: dE2000; also, that deltaC was a measurment worth taking. Reports from CN give dEab and dE2000 measurments, dEab is where i'm getting much poorer results generally, with some patches 4-8.

 

dE00: Max_2.16, Avg_0.39, White_0.24

dEab: Max_8.88, Avg_1.04, White_0.20

 

The dE00 i understand to be (very) good values...?

Of 134 patch-test, ISO:12646

dE00: max: x2 patches @ 2>, x4 patches @ 1-2.

dEab: max: x4 patches @ 4>, x8patches @ 2-4.

 

I can see from ur list (thanks for that) that dEab refers to LAB colour-space... but, what does it mean...? -"No idea what -dEab is." -Brilliant, that cheers me up for some reason :)

 

So, perhaps a better way of asking my question is (bearing in mind that the ARGB gamut numbers are excellent all-round):

-Would you, personally, be 'concerned' about the display based on this report's dE*ab numbers, despite the good dE00 numbers?

 

(Not compared to a Spectraview or CG display, but for this display, and generally agreed expectations of what it should do.)

Yeah the scrolling issue happens on this end too. So I can't really see the fine print....

You're measuring 138 patches, the average is useful but so is the one, worst patch report.

dE00: max: x2 patches @ 2>, x4 patches @ 1-2.

dEab: max: x4 patches @ 4>, x8patches @ 2-4.

No, not bad at all.

Again, I'd only be concerned with a dE 2000 value; average and max for one sample.

Thanks.

 

Again, I'd only be concerned with a dE 2000 value; average and max for one sample.

 

Sorry, i have a language issue: Are u saying there's only one dE00 colour-patch you'd be concerned with...?

-And is that a good thing?

 

(Tried uploading reports again -scrolled again :(

Yes, I'd only be concerned with the dE 2000 (if that's the formula) report and if the report provides an average, great but some reports provide a dE of the one, worst patch. So you can see the worst offender. An average is useful but doesn't tell you about the worst offender. The more patches, the more the average alone 'hides' the one worst patch difference. BOTH metrics are useful.

Ah OK, i have both metrics in the report, so good.

 

Great, thanks for your help on this. I feel a bit clearer following up with Eizo about it.

 

Best Regards :)