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Author Topic: 3 close measurements on 3 monitors: 3 color-casts!  (Read 4294 times)
Nino Loss
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« on: August 21, 2010, 07:05:17 PM »
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Thank you for any help with this:

Here is the recipe for this situation I am lacking any explanation to understand. There are two separate issues:

1) Target: UGRA  5800/1.8/120 (neutral minimum black)

2) One Probe: NEC's i1D2 (MDSVSENSOR)

3) Calibrated and profiled PA241W with Spectraview II

3) One device independent software: Quato iColor with wide-gamut matrix activated for i1D2.

4) PROBLEM #1 Check PA241W with Quato iColor gives very different readings from Spectraview (please see attachment)

5) applly Quato readings as close as possible to two more (simpler) wide-gamut monitors than the NEC PA241: EIZO S2233W, LG L227W (Reset on all of them. Cleaned out all existing profiles.)

6) PROBLEM #2 Three very close measurements on three monitors BUT Three different color-casts!


Please do see the attachment which makes everything a little bit clearer, I hope.

regards

nino


EDIT: There are no windows and no colors in this "professional" digital darkroom, neither on the walls nor anywhere else...
« Last Edit: August 21, 2010, 08:43:18 PM by Nino Loss » Logged
WombatHorror
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« Reply #1 on: August 22, 2010, 01:59:03 PM »
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One thing to keep in mind is that just moving the puck from spot to spot can easily give you +/- 50K (and that is on a strongly compensated monitor, no less!)

I measured a NEC PA241W with an i1Pro and with an MDVSENSOR2 and got very similar results.

DTP94b (old and new copies) in Quato and neither agreed with each other or the i1pro/MDVSENSOR.

I forget the details.

I also noted the NEC i1D2 seems to measure a bit differently whether it is 24C or has gotten hotter and whether it has been used for time in a row or not.
The other shift too but can be constantly recalibrated.

I did notice it was pretty crazy to measure again and again over 20 minutes, even in that span things keep changing.


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Nino Loss
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« Reply #2 on: August 26, 2010, 12:55:30 AM »
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One thing to keep in mind is that just moving the puck from spot to spot can easily give you +/- 50K (and that is on a strongly compensated monitor, no less!)

I measured a NEC PA241W with an i1Pro and with an MDVSENSOR2 and got very similar results.

DTP94b (old and new copies) in Quato and neither agreed with each other or the i1pro/MDVSENSOR.

I forget the details.

I also noted the NEC i1D2 seems to measure a bit differently whether it is 24C or has gotten hotter and whether it has been used for time in a row or not.
The other shift too but can be constantly recalibrated.

I did notice it was pretty crazy to measure again and again over 20 minutes, even in that span things keep changing.




Thank you Larry! I agree. It also concords with my experience. That's for Problem #1. What's with #2? How come that almost identical measurements produce substantially different color casts?

cheers

nino
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WombatHorror
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« Reply #3 on: August 30, 2010, 08:12:34 PM »
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Thank you Larry! I agree. It also concords with my experience. That's for Problem #1. What's with #2? How come that almost identical measurements produce substantially different color casts?

cheers

nino

perhaps those other two wide gamuts have a different spectral peaking to the primaries???
maybe you happened to measure in a less than ideal spot not representative of the average tint on one or two of them???
maybe you measured at times when the probe was actinging differently due to temp changes or something??
« Last Edit: August 30, 2010, 08:14:06 PM by LarryBaum » Logged
Nino Loss
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« Reply #4 on: September 01, 2010, 04:56:42 PM »
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perhaps those other two wide gamuts have a different spectral peaking to the primaries???
maybe you happened to measure in a less than ideal spot not representative of the average tint on one or two of them???
maybe you measured at times when the probe was actinging differently due to temp changes or something??



I will investigate this, and come back to you. I simply placed the probe in the middle of the screen. I measured one after the other, and than back again. I took out the average result.

What you are suggesting is that the results for the three screens just appear to be close? hmm... It's just that these possible small variations are related to rather strong color shifts...
« Last Edit: September 01, 2010, 05:28:21 PM by Nino Loss » Logged
digitaldog
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« Reply #5 on: September 02, 2010, 01:01:04 PM »
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4) PROBLEM #1 Check PA241W with Quato iColor gives very different readings from Spectraview (please see attachment)

Its quite possible the spectral to XYZ math is different. Its not unheard of. For example, if I open a CGATs of measured spectral data and ask for the spectral to lab conversion in MeasureTool vs. ColorThink, there are differences in the results (although its quite small). But it appears the values you have below are small too. Ideally you would measure the exact same spot with the same instrument into the same software to get those values.
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Andrew Rodney
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Nino Loss
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« Reply #6 on: September 02, 2010, 09:19:05 PM »
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Its quite possible the spectral to XYZ math is different. Its not unheard of. For example, if I open a CGATs of measured spectral data and ask for the spectral to lab conversion in MeasureTool vs. ColorThink, there are differences in the results (although its quite small). But it appears the values you have below are small too. Ideally you would measure the exact same spot with the same instrument into the same software to get those values.

Thank you Andrew. That sound reasonable. I also thought that, though I kept the measuring device at the same spot, the software was different, one the SpectraViewII, was talking to its custom mated sensor, while Quato's software talks to a stranger.

The bidg problem though, Andrew, is #2!

regards

nino
« Last Edit: September 02, 2010, 11:17:04 PM by Nino Loss » Logged
digitaldog
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« Reply #7 on: September 03, 2010, 09:46:43 AM »
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The bidg problem though, Andrew, is #2!

Well we still don’t know that the values are that close since they are being generated by different products. However, depending on the imagery (say a gray), its not unlikely that even small value differences would appear differently. If we knew that the values were all generated the same way, we could use the XYZ values to generate a deltaE value to inspect the differences which might be useful.

Its not at all uncomon to find two different software packages, all set for the same target calibration values using the same instrument to produce different results. I know that’s not supposed to happen but it does.

What many users also don’t know is that you can buy two different Spectrophotometers or Colorimeters from different companies, measure the same color and get different values! The manufacturers all use different ways to get to what we think is the same results. A new ISO spec (ISO13655 M0) is supposed to remove this disconnect but guess what? If you buy a unit today that doesn’t aim towards this spec, then a year from now, buy a newer instrument or even have your old unit repaired or recertified, its quite possible all the data you measured a year ago and all the new data you measure will not correlate! That’s a big friggin issue for many of us.
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Andrew Rodney
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Nino Loss
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« Reply #8 on: September 03, 2010, 10:00:14 AM »
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Well we still don’t know that the values are that close since they are being generated by different products. However, depending on the imagery (say a gray), its not unlikely that even small value differences would appear differently. If we knew that the values were all generated the same way, we could use the XYZ values to generate a deltaE value to inspect the differences which might be useful.

Its not at all uncomon to find two different software packages, all set for the same target calibration values using the same instrument to produce different results. I know that’s not supposed to happen but it does.

What many users also don’t know is that you can buy two different Spectrophotometers or Colorimeters from different companies, measure the same color and get different values! The manufacturers all use different ways to get to what we think is the same results. A new ISO spec (ISO13655 M0) is supposed to remove this disconnect but guess what? If you buy a unit today that doesn’t aim towards this spec, then a year from now, buy a newer instrument or even have your old unit repaired or recertified, its quite possible all the data you measured a year ago and all the new data you measure will not correlate! That’s a big friggin issue for many of us.


but for #2, the three measurements, one on every screen, I used one and the same software and sensor only! It is the NEC sensor with Quato. I than double checked and made all three measurements with the DTP94b and Quato.
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digitaldog
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« Reply #9 on: September 06, 2010, 12:23:49 PM »
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but for #2, the three measurements, one on every screen, I used one and the same software and sensor only! It is the NEC sensor with Quato. I than double checked and made all three measurements with the DTP94b and Quato.

For fun, try this. Take the measurements on one display, in the center, then on each corner. What do you end up with?
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Andrew Rodney
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Nino Loss
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« Reply #10 on: September 07, 2010, 04:33:50 AM »
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For fun, try this. Take the measurements on one display, in the center, then on each corner. What do you end up with?

Andrew,

I did this. It gave me results differing as much as from one monitor to the next, or maybe even higher. The point I am trying to make though is, that all three monitor measurements are quite close, but their visual appearance is radically different. They have different casts. How can this be?
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digitaldog
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« Reply #11 on: September 07, 2010, 07:57:07 AM »
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I did this. It gave me results differing as much as from one monitor to the next, or maybe even higher. The point I am trying to make though is, that all three monitor measurements are quite close, but their visual appearance is radically different. They have different casts. How can this be?

It could be a visual phenomena. Are they all lined up in a row, with the surround around the display all fixed to a single neutral color?
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Andrew Rodney
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tho_mas
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« Reply #12 on: September 07, 2010, 10:00:41 AM »
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I used one and the same software and sensor only! It is the NEC sensor with Quato. I than double checked and made all three measurements with the DTP94b and Quato.
and to which compensation table did you set Quatos iColor Display? It contains correction tables for their respective monitors (of course), for generic wide gamut PVA displays and for generic wide gamut IPS displays. All those correction tables will give you (very) different measurement results. If you set the same correction table for all the three monitors it won't work neither, as in this case the colorimeter won't measure the wide gamut display very good.

In part the topic is adressed in this PDF (Eizo White Paper): http://www.eizo.com/global/support/wp/pdf/wp_08-002.pdf

If you want the three monitors to match... adjust them manually/visually...
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Nino Loss
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« Reply #13 on: September 07, 2010, 10:31:34 AM »
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It could be a visual phenomena. Are they all lined up in a row, with the surround around the display all fixed to a single neutral color?

they are normally not lined up in a row, because of the difference in angle that I would get when looking at them from one single point. So they are ligned up in a way, that I should have the same angle of view. While investigating the issue, I did line them up though, only it didn't help.
The surrounding color is the neutral gray wall. Most of the time I work without light. But if there is light it is JUST 5000K, low, indirect and as evenly distributed as possible.

nino
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Nino Loss
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« Reply #14 on: September 07, 2010, 10:34:45 AM »
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and to which compensation table did you set Quatos iColor Display? It contains correction tables for their respective monitors (of course), for generic wide gamut PVA displays and for generic wide gamut IPS displays. All those correction tables will give you (very) different measurement results. If you set the same correction table for all the three monitors it won't work neither, as in this case the colorimeter won't measure the wide gamut display very good.

In part the topic is adressed in this PDF (Eizo White Paper): http://www.eizo.com/global/support/wp/pdf/wp_08-002.pdf

If you want the three monitors to match... adjust them manually/visually...

You are right, I forgot to mention that I did set each monitor to its respective compensation table.

I am aware of the workaround, to match the screens visually, just when I profile them afterwards with white point set to native, off they go again!

nino
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tho_mas
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« Reply #15 on: September 07, 2010, 10:45:23 AM »
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I am aware of the workaround, to match the screens visually, just when I profile them afterwards with white point set to native, off they go again!
I found out it's much easier - for me! - to adjust the monitor to a certain white point when I do not display only white on the screen.
I get better results when I display an image that has a large white area but also a greyscale and a mid grey area...
this (custom made) image: http://www.luminous-landscape.com/forum/index.php?action=dlattach;topic=44934.0;attach=18315;image

So maybe try to get a match in mid greys (rather than pure white) and see if this is going to improve things...
« Last Edit: September 07, 2010, 10:47:05 AM by tho_mas » Logged
Nino Loss
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« Reply #16 on: September 07, 2010, 11:21:28 AM »
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I found out it's much easier - for me! - to adjust the monitor to a certain white point when I do not display only white on the screen.
I get better results when I display an image that has a large white area but also a greyscale and a mid grey area...
this (custom made) image: http://www.luminous-landscape.com/forum/index.php?action=dlattach;topic=44934.0;attach=18315;image

So maybe try to get a match in mid greys (rather than pure white) and see if this is going to improve things...
That sounds great! I'll try that too. I have a lot of homework to do now, with all your advice  Smiley
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tho_mas
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« Reply #17 on: September 07, 2010, 11:39:30 AM »
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That sounds great! I'll try that too. I have a lot of homework to do now, with all your advice  Smiley
hopefully some of it turns out to be helpful...
I'd concentrate first on the NEC ... first when this display runs accurately I'd adjust the other displays step by step to match the NEC.
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