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Author Topic: i1 Profiler monitor QA odd results ?  (Read 5483 times)
Rhossydd
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« on: April 01, 2011, 06:09:53 AM »
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I’m getting some curious QA results from i1Profiler.
Using an i1pro spectro to calibrate (110cdm) and profile my PA271 with Basicolor 4.1.22 (aka Spectraview II in Europe). When I use the validation option I see Average DeltaE94 0.25, max 0.93, standard deviation 0.26. All pretty good I reckon.

Now if I try the display QA option in i1 Profiler with the same instrument it fails with average DE 3.09, maximum 4.88. Why the difference ?

Paul
Getting frustrated with X-Rite releasing the software, but not the licence codes!
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Czornyj
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« Reply #1 on: April 01, 2011, 08:44:12 AM »
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You're comparing apples to oranges - basICColor only validates the monitor profile - it measures same RGB patches that were used for display profile creation. Basically it just shows if the display behaves in the same way as when it was profiled.

QA in i1Profiler works in a different way - it calculates RGB values of color space of our display that should give best match to colorimetric values of CC24 patches. In this case gamut of the display may not cover all CC24 patches 100%, or the profile may not be accurate enough to give a perfect match.
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Rhossydd
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« Reply #2 on: April 01, 2011, 10:36:37 AM »
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You're comparing apples to oranges...... Basically it just shows if the display behaves in the same way as when it was profiled.
?? As I understand it it's measuring the accuracy of colours displayed on the screen.

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QA in i1Profiler works in a different way - it calculates RGB values of color space of our display that should give best match to colorimetric values of CC24 patches. In this case gamut of the display may not cover all CC24 patches 100%, or the profile may not be accurate enough to give a perfect match.
The CC24 is comfortably within the PA271's gamut and the Basicolor validation suggests the profile is accurate to less than DE1.

Having studied the results more closely it seems that all the Profiler measured results have a lower than expected luminance value. It's looking like the QA module is taking X-Rite's default 120cdm luminance target and is expecting higher luminance values than I choose to work with, so thinks the results it's measuring are wrong.
I can't see how this can be changed, so maybe this module will only be of use if using it's own monitor profiling module.
Not a lot of use to those of us that use other profiling software to benefit from hardware calibrated displays.
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Mark Paulson
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« Reply #3 on: April 01, 2011, 10:53:15 AM »
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Getting frustrated with X-Rite releasing the software, but not the licence codes!


I called Xrite and got my code right then. I was entitled to a free upgrade and sent them an email with my proof of purchase a couple of days ago and called yesterday to ask some questions and they sent the code.
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Rhossydd
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« Reply #4 on: April 01, 2011, 01:03:32 PM »
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I called Xrite and got my code right then. I was entitled to a free upgrade.....
Lucky you. I've spent a serious amount of money on GMB/X-Rite products in the past and want to upgrade, but I have to wait until they can be bothered to get the boxes out to dealers Sad

Edit: I've just got an email notifying me of dispatch of my upgrade box.
"Next day", but I doubt I'll see it until Monday and it does . At least I've little on next week to allow me some time for evaluation. The only advantage of the mess of pre-release is that at least I'll have viewed all the tutorials, read the help files and been able to print out some charts and let them dry down before measurement.
« Last Edit: April 01, 2011, 01:11:13 PM by Rhossydd » Logged
gromit
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« Reply #5 on: April 01, 2011, 06:24:57 PM »
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?? As I understand it it's measuring the accuracy of colours displayed on the screen.

No. It's measuring how closely the profile generated models the actual displayed values ... to the accuracy of the instrument. It says nothing about how "accurate" the colours are.

Try calibrating with MultiProfiler and profiling (only) with basICColor display (or whatever).
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digitaldog
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« Reply #6 on: April 01, 2011, 07:05:38 PM »
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If you have a PA, you don’t want to mess with i1P or any 3rd party software for calibration and profiling when you have the NEC software.
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Andrew Rodney
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Rhossydd
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« Reply #7 on: April 02, 2011, 01:11:32 AM »
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No. It's measuring how closely the profile generated models the actual displayed values ... to the accuracy of the instrument. It says nothing about how "accurate" the colours are.
You'll need to re-phase that, because to me how closely matched the colours are displayed is the same thing is how accurately they're reproduced.

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Try calibrating with MultiProfiler and profiling (only) with basICColor display (or whatever).
Why ?
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gromit
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« Reply #8 on: April 02, 2011, 08:10:54 PM »
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You'll need to re-phase that, because to me how closely matched the colours are displayed is the same thing is how accurately they're reproduced.
Why ?

Here's an analogy: You have a ruler and mark out 1m along a piece of wood. Next you cut the wood at the mark you made then measure the length with the same ruler. Yep 1m. This is validation. Except your piece of wood is 997mm long due to the inherent inaccuracy of the ruler.

The same with monitor calibration/profiling. Consumer grade instruments (colorimeters, spectros) are inherently inaccurate, made more so by light leakage when taking the measurements, dirt on the reference slate, off-vertical measurement with spectros etc. This is exacerbated by the different/larger gamut that colorimeters have to deal with these days. If you have a number of devices you'll notice that they all give slightly different results. I managed to achieve a dE of 0.15 for validation on my hand-picked Spectraview Reference PA271 with the best combination of software and hardware I had, but visually prefer the results I get (more neutral shadows, cleaner grayscale ramps) by using MultiProfiler alone. So that's what I use. It may be more satisfying to get your monies worth out of whatever software/instrumentation you bought, but at the end of the day it's the results that count.
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Rhossydd
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« Reply #9 on: April 03, 2011, 03:10:15 AM »
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Sorry gromit, but you're rather missing the point.
A spectro will have a degree of error both in absolute accuracy and repeatability, but that can be ascertained with testing and you can get a good idea of how accurate the instrument is in practice. For my main instrument I see better than 0.14 DE.
The data analysis module of Profiler will be able to help test and calculate these sorts of errors.

So once you know the degree of error possible for your instrument you can then go on to measure colours on different devices with a known degree of accuracy.

The problem (design failure?) of the QA module in Profiler is that it seems impossible to define what standards it's measuring to, (luminance, colour temp etc), if you haven't built a profile for it to measure. In other words, if you wish to use another software product to calibrate and profile your display with (eg Spectraview, Multiprofiler or the Eizo products) Profiler can't be used to independently validate the quality of the display. A facility that would be useful and I had thought was being included within the product.
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gromit
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« Reply #10 on: April 03, 2011, 03:35:59 AM »
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Sorry gromit, but you're rather missing the point.
A spectro will have a degree of error both in absolute accuracy and repeatability, but that can be ascertained with testing and you can get a good idea of how accurate the instrument is in practice. For my main instrument I see better than 0.14 DE.

The i1Pro isn't great for measuring darker values on monitors. I got better results overall from a Samsung branded i1D2 (came with their XL20 LED monitor) than any other device in my arsenal. The Optix XR was a good device in its day but unsuited to the PA271.

Irrespective of devices and validation results I run visual tests after calibration/profiling to test shadows/highlights for neutrality/separation, gray ramps for smoothness/cleanliness, gamut tests and real world images (skintones etc) to see if I'm happy with the results. MultiProfiler is excellent in these respects, and gives negligible difference in rendition to hardware calibration. Given the flexibility in changing white/blackpoint on the fly it's what I use. People place too much confidence in instruments (most of which cost peanuts to manufacture) and bogus numbers instead of using their eyeballs IMHO.
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Rhossydd
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« Reply #11 on: April 03, 2011, 03:51:29 AM »
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People place too much confidence in instruments (most of which cost peanuts to manufacture) and bogus numbers instead of using their eyeballs IMHO.
I guess if that's your opinion, colour management isn't really for you.
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gromit
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« Reply #12 on: April 03, 2011, 04:57:22 AM »
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I guess if that's your opinion, colour management isn't really for you.

Given a number of solutions for monitor calibration/profiling (including separating the two) I'll simply choose the one that gives the best visual results, that's all.

Try calibrating with MultiProfiler, even if you still use an instrument for profiling. You might find this beneficial!
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Rhossydd
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« Reply #13 on: April 03, 2011, 05:49:44 AM »
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Try calibrating with MultiProfiler, even if you still use an instrument for profiling. You might find this beneficial!
I tried it and didn't find beneficial when I first got the PA
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Czornyj
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« Reply #14 on: April 03, 2011, 01:49:17 PM »
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?? As I understand it it's measuring the accuracy of colours displayed on the screen.
The CC24 is comfortably within the PA271's gamut and the Basicolor validation suggests the profile is accurate to less than DE1.
The difference is, that while profiling you're measuring some RGB patches (255.0.0, 0.255.0, 0.0.255 - etc.), and then you're measuring the same patches during validation. You don't really know about the accuracy of the whole rest 16,7mln R,G,B values...

Having studied the results more closely it seems that all the Profiler measured results have a lower than expected luminance value. It's looking like the QA module is taking X-Rite's default 120cdm luminance target and is expecting higher luminance values than I choose to work with, so thinks the results it's measuring are wrong.
I can't see how this can be changed, so maybe this module will only be of use if using it's own monitor profiling module.
Not a lot of use to those of us that use other profiling software to benefit from hardware calibrated displays.
I think you're right. I've also noticed, that it has a different opinion than SpectraviewII, basICColor display/Spectravie profiler concerning the luminance value and wtpt... XRGA?
« Last Edit: April 03, 2011, 01:52:33 PM by Czornyj » Logged

Czornyj
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« Reply #15 on: April 03, 2011, 02:02:37 PM »
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correction - QA likes something, it recognizes as 160cd/m^2 luminance level.
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Rhossydd
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« Reply #16 on: April 03, 2011, 02:05:10 PM »
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correction - QA likes something, it recognizes as 160cd/m^2 luminance level.
Curious, the default is 120
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Rhossydd
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« Reply #17 on: April 03, 2011, 02:12:11 PM »
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The difference is, that while profiling you're measuring some RGB patches (255.0.0, 0.255.0, 0.0.255 - etc.), and then you're measuring the same patches during validation. You don't really know about the accuracy of the whole rest 16,7mln R,G,B values...
Obviously measuring every possible value is impractical.
The choice of using the CC24 values is actually more useful than Basicolor's values* as they are more representative of real world image values. Which why the difficulty(impossibility?) of using profiler's validation module would have been desirable.

*you can just look at the less extreme(ie real world) colours' validation values and make your own mind up. It still looks good.

It's also disappointing to see how poor the printer profile validation routine is, just print a CC24 out and get an overlay to put over it. Where's the ability to actually measure a chart and compare it empirically for validation ?
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Czornyj
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« Reply #18 on: April 03, 2011, 03:48:12 PM »
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Curious, the default is 120
L*a*b works well in certain viewing conditions, so maybe the LCD must be @160cd/m^2 to display these colors correctly? Unfortunately, I have limited knowledge on advanced color science, but considering Stevens & Hunt effects the luminance of the display has visual impact on perceived color and contrast (see page 5, 27)
http://www.cis.rit.edu/fairchild/PDFs/AppearanceLec.pdf
« Last Edit: April 03, 2011, 04:18:16 PM by Czornyj » Logged

digitaldog
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« Reply #19 on: April 03, 2011, 04:30:21 PM »
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Sorry gromit, but you're rather missing the point.
A spectro will have a degree of error both in absolute accuracy and repeatability, but that can be ascertained with testing and you can get a good idea of how accurate the instrument is in practice. For my main instrument I see better than 0.14 DE.

I agree with gromit and the ruler analogy. Without a higher grade, known reference instrument, you can’t possibility known how well the i1 did in measuring the colors. If it were doing such a superb job, why would you be running this variation process over again unless you were trying to figure out if something happened within the process (like the puck falling off the display)? And that’s about the only useful functionality of such ‘validation’ to come back from the process, see it looks butt awful and then wanting confirm numerically it was butt ugly. But why its butt ugly isn’t defined. Given that the software producing this validation often sends colors within colorspace of the display that will produce good values, the process is more a feel good function than anything useful. Now you have a reference grade spectroradiometer and software you can use to examine both its measurements and the i1? That could be useful.

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No. It's measuring how closely the profile generated models the actual displayed values ... to the accuracy of the instrument. It says nothing about how "accurate" the colours are.

Exactly.
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Andrew Rodney
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http://digitaldog.net/
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