What exactly happened between CIE76 and CIE94/2000? - AVS Forum
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post #1 of 19 Old 08-23-2014, 03:08 PM - Thread Starter
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What exactly happened between CIE76 and CIE94/2000?

I have a medium form of protanopia (color deficiency for the color red in my visual system) and as such should be more sensitive to luminance errors, but less sensitive to chromaticity errors in the red spectrum.

I have to put this up front as the following is based on my visual impressions of images vs. measured color errors.

What I have found though, is that my visual recollection of whats on the screen more closely resembles what is measurable within the CIE76 color error formula than the CIE94 or 2000 formulas.

I've tested this with two different "near perfect" (saturation tracking always significantly below dE 3 panels (Sony 42W650A and 55W905A).

On the W650A I see a VERY noticeable pink tint on certain pastel colors - and sure enough - once I switch to CIE76 for the saturation tracking - cyan (dE 5) and magenta (dE 4) at >85% saturation are breaking out. Also on the same device there is a more significant color error hidden at red 95% saturation which does not show, when you are only looking at the usual 5 steps per color.
With CIE2000 - all errors (except red at 95% (dEca4)) are below dE 3.

On the W905A It is even more apparent as the device - according to CIE2000 has close to perfect greyscale, color and saturation tracking across the board, with all dEs (even in color checker) near or below dE 2. On that device I see a slight green tint in critical viewing - and sure enough - once CIE76 is applied - it shows green, magenta and to a lesser extent yellow breaking out at > 90% saturation. Also on the same device there is a more significant color error hidden at green 87%, which again, doesnt show up, when you are looking at the usual 5 steps per color. This time this error is also below dE 3 if you are measuring it in CIE2000, but it breaks out to dE 4,2to5 (one steping the color slider) in CIE76.

When reading up on what changed in between CIE76 and CIE94 ColorWiki shows that at that time a "fudge factor" was introduced specified as "RIT/DuPont tolerance data derived from automotive paint experiments".
http://www.colorwiki.com/wiki/Delta_...ifference#dE94

Does anyone have more information and or data on how this changed the "usual" color targets in the CIE triangle?

I'm asking because I can see that the difference introduced at that stage was significant and resulted in - from my visual point of view - MASKING certain color errors that would have been measurable otherwise.

The different weighing of L* ("lightness") introduced in dE2000 has far less of a measurable impact then the changes that took place in between CIE76 and CIE94.
-

Regardless of what "RIT/DuPont tolerance data derived from automotive paint experiments" turns out to be and keeping in mind that I personally see colors slightly different that the majority of the population -

I found it more and more common in reading up on reviews vs. critical viewing impression that not me alone, but also other people notice certain, unmistakeable color errors (after calibration), that dont show up in "normal" measurements provided by review sites f.e.

On the one side there are faults hidden "between the lines" (5 saturation measurements per primary/secondary color are just not enough), on the other side - I visually recognize color tints, that strangely enough correspond with what the display measures under CIE76 - in two separate cases.

If there are any impressions on your part on the difference between CIE76 and CIE94/2000 in practice, or if there is any one that can "illuminate" whats behind the "RIT/DuPont tolerance data derived from automotive paint experiments" fudge factor data - I would appreciate it.

As for now, just take it as a personal experience report of one guy who saw a green color tint in critical viewing on a avg dE 0.80 (CCSG) device - with a masked green error of dE 5 at 87% and arround dE 4 at 100%, when measured at CIE76, which both totally vanished (below dE 2) from the measurement results when measured at CIE2000.

Last edited by harlekin; 08-23-2014 at 03:56 PM.
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post #2 of 19 Old 08-23-2014, 03:49 PM - Thread Starter
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After some googleing:

Quote:
The RIT–DuPont dataset (5) the combined dataset developed from three experiments (2–4) was based on experiments using color-difference pairs that were an automotive lacquer coating sprayed onto primed aluminum panels. In addition to the many hours needed in producing the raw samples, a great deal of time and labor was needed to prepare the samples for experimentation. A total of 959 sample pairs were produced in this manner for the three experiments, in which nineteen color centers were gauged. Because of the amount of labor and time necessary to produce these sample pairs, measuring color tolerances throughout color space is prohibitive when using this type of stimulus. Strocka, Brockes, and Paffhaussen (8) point out that at least 150 color centers ought to be investigated as a thorough basis for an empirical color-difference formula.
src: https://ritdml.rit.edu/bitstream/han...cle06-1999.pdf

Oh how fun. With CIE94 an "unempirical" (= esoteric) weighing factor based on the perception of nineteen colors was introduced into the CIE formula.

Coupled with this:
Quote:
However, it is probably unwise to assume that weighting functions derived from perceptibility data can be linearly scaled to define acceptability thresholds. In one study of samples produced by four-colour offset lithography, it was found that CIE94 performed no better than dE*ab in predicting acceptability weightings and thresholds (21). CIEDE2000 performed little better in predicting this data set, and it was suggested that weighting functions derived from perceptibility data may not be able to make better predictions of acceptability thresholds unless the parametric factors are modified according to the region of the colour space (thus becoming functions rather than constants).
src: http://*******/6Vh4Kp

It makes the CIE94 (and CIE2000 formula) which introduced those extensive weighing (=fudge) factors unscientific, and ultimately unusable for assessing the color performance of displays.

Wouldnt that be a fair assessment?

And again, shouldn't someone tell the public?

Last edited by harlekin; 08-23-2014 at 04:14 PM.
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post #3 of 19 Old 08-23-2014, 05:07 PM
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Everything about color is observed, very little of our perception of color is hard fact.

After you've measured the spectrum in watts per steradian per nm all the transforms are based on observed performance of test subjects.

dE2000 is the best that we have, it's not perfect, but as the evolution of the standard it's certainly an improvement over the previous implementations.

So your assessment is not correct. The PHDs that established the standards at http://www.cie.co.at/, are the same people that have been responsible standardizing the majority of color science.

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post #4 of 19 Old 08-24-2014, 12:24 AM - Thread Starter
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Ok, then next question - where does the "everything below a dE of 3 is not perceptible to the human eye" guideline originate from?

According to http://*******/6Vh4Kp -

Quote:
In one study (65) a mean perceptibility tolerance of 3 dE(ab) was found; mean acceptability tolerances were found to be 6 dE(ab), but a simple linear scaling from perceptibility did not model the results well.
src: http://*******/6Vh4Kp
footnote 65 refers to: Stokes, M., Fairchild, M. D. and Berns R. S. (1992) Colorimetrically quantified visual tolerances for pictorial images. Proc. TAGA Conf., 757-778.

So the non perceptibility of dE 3 seems to refer to the CIE 76(ab) scale -

Now lets see how much CIE 76(ab) differs from CIE 2000 in my two practice examples:

42W650A on the left, 55W905A on the right



Again, I have a problem with that. It seems that every CIE standard starting from CIE 94 just hides color errors - while at the same time the "below dE 3 rule" never was meant to be used for anything other than CIE 76(ab). Regardless of the "weighing problem" bias.

Any comments on that?
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post #5 of 19 Old 08-24-2014, 12:51 PM
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dE has always, ALWAYS meant to have 1 be the very minimum level of differentiation under ideal circumstances.

Also there is nothing about hiding error, dE76 is just a pure distance formula in 3D space. The evolutions in dE have made it more consistent so that an error of 1 is the minimum perceptible difference across a more uniform area.

Probably the best tool is something like the color comparator in CalMAN that simply shows the RGB differences, if you've have a reasonably calibrated screen you can actually see the visible difference and decide for yourself if the error is too much or not.

The use of 3 as a tolerance is typically given with the qualification in moving video on two displays next to each other. With that qualification it is relatively true even with dE 2000.

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post #6 of 19 Old 08-24-2014, 03:34 PM - Thread Starter
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Thank you for your response - now back to the principal reason for this thread - arguing.

Let me say this - on the argument level alone this is a lost cause.

Retreating from dE 3 to dE 1 as a measure of rebuttal is - calculated, but does not solve the problem.

Underlining that CIE 94 and the subsequent 2000 standard were never meant to "hide"(/"declare hidden") display faults - when effectively the introduced fixed (!) fudge factor with CIE94 was JUST THAT (literally!) is - stretching it.

Also dE 1 on what scale - as we just saw, dE 3 went from "meaning at least something by scientific standards" to "totally meaningless by todays CIE standards" - because the scale of what this measurement once "meant" over time seemed to have decreased by a factor of 3, without seemingly anyone noticing that at all.

At primary/secondary measurements at 100% saturation never the less. Which are probably the first six colors you would look at doing any kind of perceptual testing.

Calman (just to name one) is still providing green and red lines for the dE 3 and dE 5 thresholds and If I don't get anyone coming up with the definitive study that shows that this is applicable to CIE standards starting from CIE94 onward - the only thing that keeps repeating to ring true here is -

that in this industry any scientific approach was long rejected and replaced by gatekeepers with commercial interests at heart.

If the net effect of the changes in your measuring standards over the last 2 decades was to reduce the sensitivity of your scales by a factor of three - thereby invalidating perceptual studies that found that a mean error of dE 3 was below the perceptional threshold - but in return still keeping the green and red line "targets" in Calman (just to name one) at the dE 3 (and dE5) level - it doesnt need a genius to summarize what has happened here.

The "goal" all of a sudden became "more reachable" for a broader set of customers. TV manufacturers are happy. Meter vendors are happy. Software vendors are happy. Calibrators that primarily look at numbers or "Calibration reports" are happy. Customers get told that their TVs are better than they actually are.

Everybody wins in the end - if they just try to believe a little bit harder...

Last edited by harlekin; 08-24-2014 at 03:48 PM.
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post #7 of 19 Old 08-24-2014, 04:29 PM
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Personally I like to keep the conversations technical.

The CIE thinks dE2000 is the best metric for describing color error, so that's what we us. We are constantly working on improving our product and our AutoCal threshold is 0.5 dE 2000. Our goal is to produce the best results possible. The changes we make are to help consumers easily attain that goal. If we just wanted to make pretty charts we have lots of ways to do that.

Personally, like I mentioned above, use the color comparator chart as the arbiter if it's good enough. We certainly aren't trying to push the error thresholds higher. Just look at the dE2000 autocal algorithm we introduced that substitutes JND increments in the place of L*. We are always in the pursuit of more accurate calibrations and I believe any of our longtime customers can attest to progress towards that goal.

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post #8 of 19 Old 08-25-2014, 07:02 AM
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To that point I just used Autocal over the weekend with my VT60, kudos to the Calman team I got great results visually and chart wise. Lots of progress made in the last few years

65VT60(Calibrated by Chad B)
55ST60(Calibrated by Chunon)
Darbee DVP5000
Sony BDV-F7 3dbluray/soundbar
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Dish Network with Hopper/Super Joey
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post #9 of 19 Old 08-26-2014, 02:09 AM - Thread Starter
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Its over.

We just trust the body that reduced the sensitivity of the scale by a factor of 3 - using a linear factor - which has proven non adequate in all perceptual studies I've read, based on only 19 color assessments, when even the color checkers we use today are using over 90 - and three different scientists can agree that at least looking at 150 color points distributed over the entire spectrum would be needed for a - quote - scientific color formula.

Trust. Thats what it comes to - nevermind reproducibility of experimental settings - nevermind the scientific method.

Nevermind that the deltaE target of 3 seems to not even be based on anything that is still attributable to the CIE 94 and CIE 2000 charts (please anyone - find me one hopefully scientific reasoning on why we use the dE 3 threshold with CIE 2000) - and is just used to hoodwink coincidental bystanders to think that "nothing significant has changed" - when over the last three decades the sensitivity of the measurement scale seemingly was reduced by 300% - when looking at the 6 most obvious color points - nevertheless.

As a cherry on the cake the last posting - completely at random - thanked a software package for doing an automated greyscale run on the TV - which "made things look great".

Just as a sidenote - the greyscale in my two practice examples confirm to both CIE 76uv and CIE 2000 with max dEs of below 1,5, its when looking at the saturation curves for colors in both examples that you see the potential to hide significant color errors.

So that statement boils down to "my colors look great" - which, as a reaction deserves the most emphatic "well, then - great for you" - I can muster up. Can we now please get back on topic.

Well - no, coincidently we cant - because there is one more "believe" that is sold in here now and that is "Lots of progress [was] made in the last few years *smilieface*" - which seems to summarize the total neglect of everything I have worked to surface in this thread, by means of - smilieface.

Because who needs any sort of proof or even a well constructed argument when they have - faith.
-

Because curiosity drives my interest in most part - could someone actually post a saturation graph of one of the just mentioned Panasonic panels - after calibration - that shows their performance according to the CIE 76ab and CIE 76uv (and CIE 2000) scales? Im interested in comparative data.

Last edited by harlekin; 08-26-2014 at 02:35 AM.
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post #10 of 19 Old 08-26-2014, 02:59 AM - Thread Starter
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Also in September a new CIE symposium is going to be held in the Orangerie of Schloss Schönbrunn -

http://div2.cie.co.at/?i_ca_id=939

- where the overarching theme of the get together is -

Quote:
New international measurement standards are being developed by the International Commission on Illumination (CIE). In these standards special emphasis is given to the evaluation of measurement uncertainties.
To me this qualifies as a politically correct phrasing for "our fudge factor was bogus". So why is no one calling this at the face value?
--

I will now sum up the problematic factors I have experienced in getting to know this "industry" in a bullet point list.

  • Critical color errors over large fields in the spectrum easily can be hidden by only using 5 measurements per color saturation, instead of lets say 15. The additional amount of time that would be necessary to increase the amount of measurements would be less then two minutes per calibration.
  • As gamma is not defined in the Bluray standard the original intent of the director (colorwise) still has to be guessed and most likely varies on a case by case basis. Gamma does influence color reproduction.
  • Color filters on most (expensive) colorimeters and spectroradiometers degrade over time and need recalibration every 6 moths. Recalibration costs are in the hundreds (USD). Also - compliance rates to do this seem very low (?).
  • With colorimeters the spectrum of light that comes off of the devices has to be known - or more likely "anticipated" to apply correction tables to get any kinds of usable results. On current devices correction tables in large parts are few in numbers and havent changed for years - even though one "upsell" vendor of the i1d3 mentions on his website that there is a "huge variance" - especially in LCDs, with the jury still out on OLEDs.
  • Clearly NO ONE seems to know why the deltaE 3 threshold is used at all on the CIE 94 and CIE 2000 scales - or to what effect.
  • The fudge factor introduced by CIE 94 (and still active in CIE 2000) was rejected by SEVERAL scientific studies (in terms of accuracy). It is based on assessing only 19 color points in the spectrum.
  • The fudge factor more critically is linear - therefore already broken on a theoretical basis alone

  • The CIE seemingly seems to recognize this cluster*f* as problematic - but it isnt voiced or even recognized in our circles. Much less so in the consumer realm.

Talk about multiple system failures...

And talk about trust.

Last edited by harlekin; 08-26-2014 at 03:36 AM.
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post #11 of 19 Old 08-26-2014, 03:15 AM - Thread Starter
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Also - you are happily invited to join the CIE symposium in september - at some very reasonable rates...

Quote:
Price*
:
Tutorial: EUR 550,--/Symposium: EUR 150,--/Both: 650,--
Students: EUR 275,--/EUR 75,--/EUR 300,--
Members of CIE National Committees: EUR 400,--/EUR 100,--/EUR 450,--
Accompanying Persons: EUR 120,--
(Note that all prices are net and subject to 20% VAT)
http://files.cie.co.at/729_General%20Information.pdf

As the venue is literally 5 minutes away from my home, and I am a student - I might even attend the event - just for the situational absurdity I certainly would enjoy - although I'm afraid when paying to get to hear excuses, the joke might be on me there...
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post #12 of 19 Old 08-26-2014, 04:13 AM
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I was commenting on the new de2000 formula autocal uses. Enjoy the dialogue with yourself
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post #13 of 19 Old 08-26-2014, 11:08 PM
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Quote:
Originally Posted by harlekin View Post
Also - you are happily invited to join the CIE symposium in september - at some very reasonable rates...


http://files.cie.co.at/729_General%20Information.pdf

As the venue is literally 5 minutes away from my home, and I am a student - I might even attend the event - just for the situational absurdity I certainly would enjoy - although I'm afraid when paying to get to hear excuses, the joke might be on me there...

FYI, spectroradiometers don't have color filters in them. They use diffraction gratings.

Tyler Pruitt - Technical Liaison at SpectraCal
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post #14 of 19 Old 11-24-2014, 01:30 PM
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Quote:
Originally Posted by WiFi-Spy View Post
FYI, spectroradiometers don't have color filters in them. They use diffraction gratings.
And diffraction gratings use the principle of breaking down light by diffraction through lines etched onto glass with a laser. Hence they never need recalibrating since the distance between the lines remains constant.
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post #15 of 19 Old 11-24-2014, 05:28 PM
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Quote:
Originally Posted by TaichiKid View Post
And diffraction gratings use the principle of breaking down light by diffraction through lines etched onto glass with a laser. Hence they never need recalibrating since the distance between the lines remains constant.
They are physical devices, and stuff can happen to them. A knock for instance, could shift the position the light strikes the diffraction grating, shifting the wavelength calibration - that's why something like the i1pro2 has a reference LED to help calibrate out wavelength changes. Dust can build up on the optics, reducing readings. Temperature changes can shift the relationship between elements (such as the distance between the etched lines), etc. Some of this can be calibrated out with normal instrument calibration, and some can't, hence the yearly certification and/or recalibration of spectrometers for those who have to prove that their readings are traceable to a standard.

In my experience yes, they are pretty stable, but no, they aren't perfect. Same goes for colorimeters - some are pretty stable, some seem less so, depending on the quality of the optics, and what has happened to them.
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post #16 of 19 Old 11-24-2014, 10:35 PM
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Quote:
Originally Posted by gwgill View Post
They are physical devices, and stuff can happen to them. A knock for instance, could shift the position the light strikes the diffraction grating, shifting the wavelength calibration - that's why something like the i1pro2 has a reference LED to help calibrate out wavelength changes. Dust can build up on the optics, reducing readings. Temperature changes can shift the relationship between elements (such as the distance between the etched lines), etc. Some of this can be calibrated out with normal instrument calibration, and some can't, hence the yearly certification and/or recalibration of spectrometers for those who have to prove that their readings are traceable to a standard.

In my experience yes, they are pretty stable, but no, they aren't perfect. Same goes for colorimeters - some are pretty stable, some seem less so, depending on the quality of the optics, and what has happened to them.
In my opinion, having designed & built various laboratory instruments, these problems can be overcome if the instrument is properly engineered. For example, cast a holder for the grating in an aluminum holder. Seal the holder with grating in a dustfree chamber, along with its associated sensor. And I don't honestly think that the expansion coefficient of glass makes a measurable difference in even a genetics lab...

There are a lot of fields which use the glass diffraction gratings, and I would have to see an independant published study of why they would need 're-aligning' yearly to put any credence to such a practise. I can understand why the manufacturer would offer such a service, though... Just my skeptical nature, I guess.
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post #17 of 19 Old 11-24-2014, 10:40 PM
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One thing I've been wondering about more recently is the type of sensors used (e.g. CMOS, CCD). Do the properties of the sensors themselves change over time (i.e. their sensitivity and/or spectral flatness of response)?
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post #18 of 19 Old 11-24-2014, 11:24 PM
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Quote:
Originally Posted by TaichiKid View Post
In my opinion, having designed & built various laboratory instruments, these problems can be overcome if the instrument is properly engineered.
Instruments typically used for Video profiling and calibration are not laboratory instruments, they are field instruments, and the price and portability reflects this. But even laboratory instruments require re-certification of you wish to claim standards traceability.
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post #19 of 19 Old 11-28-2014, 07:19 AM
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Here we go again; another thread hijacked. People, stick to the subject. Harlekin has posed a question and it is not on the inner workings of spectrometers or colorimeters, if you need to bring yourselves back to the subject review the first posting.

This individual has his heart set on arguing. If you wish to partake with him in this discussion then show respect and keep to the subject; other wise start your own thread. I myself have found that I no longer wish to engage in debating with him as his desire is to argue not to learn. With this said, I feel he has the right to post his questions and have answers without having the thread being polluted by the aforesaid "Hijacking".
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