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post #61 of 89 Old 10-21-2014, 06:31 PM
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Originally Posted by johnfull View Post
Grayscale is improved by using B+Y for a large portion of the
monochrome image. Having only two variables makes it much
cleaner. I think that the blue LED is fooling either our eyes or
the instruments designed to serve our eyes (who is boss?).
I jumped into the fray with a calibrator over the yellow results
on another brand without the yellow pixel, so you are probably
right that it is the blue, one being the complement of the other,
I'm hoping for a breakthrough better excitor -- maybe ultraviolet
LEDs to drive Quantum Dots. First, we have to curve all the
screens, though...
It seems to me that this thread has been thoroughly high jacked. I wonder, even, if the original poster is still here.
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post #62 of 89 Old 10-21-2014, 06:43 PM - Thread Starter
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Apparently the attachment did not take. it was apparently too large. Browse, instead, to this site to get started:

http://www.lightillusion.com/percept...our_match.html
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Originally Posted by john stephens View Post
See FSI's discussion of using a Perceptual approach to calibrating some of these new technology based displays. Proper setting of the white point is key to all subsequent analysis. Browse to their web site and consult with some real Color Theory Physicists!
To get started, read this attached .PDF from FSI:
So this is fascinating. Basically, if I'm understanding the gist correctly, it's saying that some new display technologies (whether they are considered good or bad) do not lend themselves to traditional calibration methods and/or tools. And furthermore, the best way to adjust for this is to use the human eye to make a subjective judgement!! (albeit on the basis of second "normal" display). While this conclusion/approach may be true it is quite shocking for me to hear because it seems to fly in the face of most of the experts on the calibration forum(s) who religiously promote exact standards and impartial equipment (not the human eye). I even think the link seems to sort of bolster what johnfull has been saying, at least to some extent.

I'd be extremely interested to hear what some of the established forum members have to say about the FSI discussion especially as compared to approaches like trying to mess with the contrast or manually shifting the white point.
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post #63 of 89 Old 10-21-2014, 07:13 PM
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Quote:
Originally Posted by robarivas View Post
So this is fascinating. Basically, if I'm understanding the gist correctly, it's saying that some new display technologies (whether they are considered good or bad) do not lend themselves to traditional calibration methods and/or tools. And furthermore, the best way to adjust for this is to use the human eye to make a subjective judgement!! (albeit on the basis of second "normal" display). While this conclusion/approach may be true it is quite shocking for me to hear because it seems to fly in the face of most of the experts on the calibration forum(s) who religiously promote exact standards and impartial equipment (not the human eye).
The eye (or human visual system) is an excellent null detector. That is, while you can't trust yourself to adjust your white point to what you think D65 is (based on your own memory), if you have two adjacent patches, you can determine with high precision whether these patches differ. And that is all that is required here (I haven't read the flander's document fully yet, but I think I get the gist). The idea here is that the accuracy of the human visual system in detecting a difference between a trusted reference display and a display which suffers metameric failure is going to be better than trusting the instrument alone. Now an interesting question is this: If the metameric failure is due to observer metamerism, then this technique is going to produce good results for the particular observer who did the match. If, however, the metameric failure is primarily due to imperfections in the instrument, then this technique should produce a result that is good across a range of observers.

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Originally Posted by robarivas View Post
I even think the link seems to sort of bolster what johnfull has been saying, at least to some extent.
I think Johnfull is confused. He is confusing gamut shape issues with metameric failure issues. In other words, he is blaming an allegedly poor choice of primaries (in terms of their inability to cover certain areas of the gamut) for faulty instrument readings.

Last edited by spacediver; 10-21-2014 at 07:23 PM.
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post #64 of 89 Old 10-22-2014, 02:11 AM
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"...I think Johnfull is confused. He is confusing gamut shape issues with metameric failure issues. In other words, he is blaming an allegedly poor choice of primaries (in terms of their inability to cover certain areas of the gamut) for faulty instrument readings.[/QUOTE]

The Quattron sets are so seldomly discussed, forgive me for talking
about 2 different issues in the same breath.
There is a general problem with all current white LEDs in making
too much of the allegedly wrong blue light -- a narrow spike that
is slightly too short of a wavelength. It doesn't miss part of the
gamut so much as dilute blue/greens with violet. It also seems to
be reading much higher on equipment than what the eye detects, which makes calibrations come out too yellow to compensate.
The second issue is purely Quattron's -- the use of the yellow
wavelength of the phosphor coating to create more white light with
the excess blue from the LED. This seems to be an opportunistic
effect and not the original intent of the 4-color system, but it is
effective at producing a neutral white light and grayscale.
Related to this is the hope that a better backlight source can be
gotten that allows a longer wavelength blue and a shorter wavelength
green to fulfill Quattron's original mandate to expand the middle
of the spectrum in a robust fashion. Gamut coverage is not the
concern so much as purity of secondary colors (eg., cyan) and
intensity to match that of primaries. Yellow was never a problem
to reproduce, but it certainly would be if a deeper green were
used as one primary, as Sony found with Quantum Dots.
There is no way to have intense yellow and cyan both with only
three primaries. Is it worth insurrection in the industry? Sharp
has already done the deed and should make good on the promise...
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post #65 of 89 Old 10-22-2014, 08:39 AM
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Quote:
Originally Posted by robarivas View Post
So this is fascinating. Basically, if I'm understanding the gist correctly, it's saying that some new display technologies (whether they are considered good or bad) do not lend themselves to traditional calibration methods and/or tools. And furthermore, the best way to adjust for this is to use the human eye to make a subjective judgement!! (albeit on the basis of second "normal" display). While this conclusion/approach may be true it is quite shocking for me to hear because it seems to fly in the face of most of the experts on the calibration forum(s) who religiously promote exact standards and impartial equipment (not the human eye). I even think the link seems to sort of bolster what johnfull has been saying, at least to some extent.

I'd be extremely interested to hear what some of the established forum members have to say about the FSI discussion especially as compared to approaches like trying to mess with the contrast or manually shifting the white point.
Make sure you thoroughly understand the article and that you attempt to carry out this regiment. Which, BTW, includes all the other normal steps of a traditional calibration. Heed spacedriver's comments above, on the human eye's ability to to compare two adjacent patches re white point. All of this is consistent with the concepts addressed by the the Bradford Matrix. Be humble, Color Theory is a very complex aspect of Physics!
Put another way, you can take your high level digital SLR and take a photo of that off color white patch, then later ask the camera what color temperature it saw. All of this is about properly readjusting the WP to a desired D65. This, again, in my humble view.
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post #66 of 89 Old 10-22-2014, 06:13 PM
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Originally Posted by johnfull View Post
"...Any perceived errors that result from using a colorimeter are a function of how different your vision is from the standard observer and how different the colorimeter filter functions are from the standard observer, and have nothing to do with an imaginary lack of sensitivity to yellow. These perceptual errors are accentuated by displays with narrow spectral peaks, this is a well known issue in colorimetry."

So, to choose a medium-hi white temperature setting and
smooth out the humps of discoloration with either a 2-point
or a 10-point adjustment is not at all recommended?
I haven't seen a calibration from a colorimeter that comes close
to the clean white that can be generated with the eye on these sets.
Three different folks have posted colorimeter/software calibrations
and all but one of more than a dozen users prefer my settings to
those. Theirs result in a yellowed-white. No one is answering why
the results come out wrong! I would prefer to set up my Movie
setting with 10 Point, properly calibrated and have fudged the
results of those guys' settings with a bit of blue to decent effect.
But then there is the fleshtone problem which they don't even
begin to solve and they resort to turning the Global Tint control (!).
The Quattron sets have been out for 5 years and the calibration
community has preferred to malign rather than to innovate. It's what
comes when innovation is from a relatively small player and is not
adopted by more. It doesn't mean it's not a good innovation but
simply that the market weeds out innovations all the time.
Sharp was a pioneer in flat screens, just as a reminder...
I noticed that you never mention using any other equipment other than a AVS disc. You seem to be negative on so many aspects of calibrating. Are you self-taught? Did you take any courses? Almost everything you mention especially regarding backlights, pixel wavelenghts and so on and so on, I have never heard of. Have you ever calibrated anything else other than a Sharp? I am really finding it to impossible to follow you. When I try to look up what you mentioned in your postings, I either can't find anything or the information on Google counters what you say.

Last edited by Phoenix_001; 10-22-2014 at 06:20 PM.
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post #67 of 89 Old 10-23-2014, 02:13 AM
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Quote:
Originally Posted by Phoenix_001 View Post
I noticed that you never mention using any other equipment other than a AVS disc. You seem to be negative on so many aspects of calibrating. Are you self-taught? Did you take any courses? Almost everything you mention especially regarding backlights, pixel wavelenghts and so on and so on, I have never heard of. Have you ever calibrated anything else other than a Sharp? I am really finding it to impossible to follow you. When I try to look up what you mentioned in your postings, I either can't find anything or the information on Google counters what you say.
I'm results-oriented. I have tuned up TVs since the days of
bias and drive controls on the back of bulky cabinets.
I know the basics of color and will learn the interactions of the
various controls till I master them. The Sharp Aquos Quattron
models have been shunned by professional calibrators because they
take a lot of time and patience to tame. I don't blame the guys
who must go by the book because of the crush of schedule, but
someone needs to work on these sets because they are screwed up
out of the box. I have a thread where the overwhelming majority
of people with the same set have found my settings satisfactory.
This doesn't mean I can fix any set or solve every problem.
But as long as the professionals are unwilling to take on this
technology -- now 5 years old -- there will be a need for hacks
like me. I'm fascinated by color perception and find many of the
discussions here quite exciting. I'm sorry if I have given you the
impression of a monkey with a typewriter. Do you own a Quattron?
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post #68 of 89 Old 10-23-2014, 09:46 AM - Thread Starter
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Other than the comparison to a reference display is there another way to come up with a reasonable alternate white point? I've heard of Judd-Vos. Would that work? And if so, what are the exact x y coordinates of the Judd-Vos white point? (I wasn't having much luck googling them)
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post #69 of 89 Old 10-23-2014, 10:41 AM
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Quote:
Originally Posted by robarivas View Post
Other than the comparison to a reference display is there another way to come up with a reasonable alternate white point? I've heard of Judd-Vos. Would that work? And if so, what are the exact x y coordinates of the Judd-Vos white point? (I wasn't having much luck googling them)
AFAIK, Judd-Vos is just another "standard" observer model ... The target white-point would still be D65, although you might(probably will) get a different "color" of D65 due to the differences in the CIE31 2deg and Judd-Vos observer models. ... Are we completely confused yet?
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post #70 of 89 Old 10-23-2014, 10:58 AM
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post #71 of 89 Old 10-23-2014, 12:23 PM - Thread Starter
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Quote:
Originally Posted by zoyd View Post
D65 does have different target coordinates when using other CMFs, sotti quotes some values here.


Awesome zoyd. Thanks. I'm wondering which of these might be preferable to use for my situation (and why)?


D65 with StandardObserver_2_Degree
x 0.3127115954, y 0.3290084044

D65 with StandardObserver_10_Degree
x 0.3138053150, y 0.3309763442

D65 with JuddAndVos_ModifiedCIE_2_Degree
x 0.3159923048, y 0.3350360907

D65 with CIE_170
x 0.3135398703, y 0.3309292947

D65 with CIE_170_Schanda_Csuti
x 0.3143893616, y 0.3307062293
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post #72 of 89 Old 10-23-2014, 12:28 PM
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2 degree is what is typically used.

The Schanda Csuti modified the most current research I have seen done on the topic.

With CalMAN and spectrophotometer you can select one of the alternate color matching functions. Our target numbers don't update automatically, so you'll have to plug new targets into a custom gamut.
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post #73 of 89 Old 10-23-2014, 04:04 PM
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Originally Posted by robarivas View Post
Awesome zoyd. Thanks. I'm wondering which of these might be preferable to use for my situation (and why)?
Judd-Vos is recommended for OLED type narrow primaries by Sony so I would start with that.
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post #74 of 89 Old 10-23-2014, 06:16 PM - Thread Starter
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So I plugged in these alternate white points and per the CIE diagram it appears that they correspond to color temps lower than 6500K thus actually causing my dE's to increase. Not the result I was hoping for. So I think I'm left with the following options:

1) Adjust my white point by eye using a reference display as a guide.

2) Reduce my contrast (and try to deal with the resulting greyscale mistracking) with the hope that the reduced contrast minimizes my "with gamma" dE enough to be worth it

3) Push up my white point to a slightly higher but somewhat arbitrary temp along the daytime locus (does this just trade out true errors for pretty looking charts??)

4) Leave everything as is and just suck up the high "with gamma" dE but enjoy the low chromaticity error

As always I'd love to hear feedback on these choices.
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post #75 of 89 Old 10-23-2014, 06:26 PM
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That's not how it works. You plug in the alternate white point and then minimize gray scale dE using the JV CMFs with your D3 or spectro
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post #76 of 89 Old 10-23-2014, 06:56 PM - Thread Starter
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That's not how it works. You plug in the alternate white point and then minimize gray scale dE using the JV CMFs with your D3 or spectro
Hmmm...could you explain "using the JV CMFs with your D3 or spectro" further or direct me to an educational link that explains this in detail? Also, I assume spectro means spectroradiometers (I'm never going to get one of those) but what does D3 mean?
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post #77 of 89 Old 10-23-2014, 07:21 PM
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The idea is to use the alternate CMF during the measurement process instead of the standard 2 deg. CMF. You can do this using HCFR or ArgyllCMS with either a spectrometer, an i1 display pro (D3), or spyder 4 by selecting the appropriate CMF prior to doing your readings. I believe CalMAN supports it for spectrometers but not the colorimeters.
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post #78 of 89 Old 10-23-2014, 07:44 PM - Thread Starter
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I have the Spyder4 and I use HCFR so how would I specifically go about selecting the alternate CMF in HCFR? I thought it was just a matter of changing to a custom white point under Preferences-->References and typing in the alternate x and y coordinates.
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post #79 of 89 Old 10-23-2014, 11:34 PM
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Quote:
Originally Posted by zoyd View Post
D65 does have different target coordinates when using other CMFs, sotti quotes some values here.
Right ... I was working the math backwards since the OP's goal seems to be to shift the actual visual color of grey to compensate for something (I forget.)

But yeah, if you're measuring an actual D65 reference target, one would expect to get different x,y coordinates with different CMFs. And, no-doubt, different coordinates for the R.709 primaries as well ...
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post #80 of 89 Old 10-23-2014, 11:36 PM
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Originally Posted by robarivas View Post
I have the Spyder4 and I use HCFR so how would I specifically go about selecting the alternate CMF in HCFR?
It should be one of the options under the 'meter setup' dialog.
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post #81 of 89 Old 10-24-2014, 08:31 PM - Thread Starter
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Are you referring to this? If so how do I determine the values to enter in each of the 9 boxes for whatever alternate CMF I decide to try?
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post #82 of 89 Old 10-24-2014, 11:26 PM
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Are you referring to this? If so how do I determine the values to enter in each of the 9 boxes for whatever alternate CMF I decide to try?
No. ... I don't have the program on this machine. But going from memory: On the "top" line you click on the meter in the "Sensor" box. That should get you to the right dialog.

Alternatively, through the menus: "Measures" -> "Sensor" -> "Configure" ... IIRC
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post #83 of 89 Old 10-25-2014, 06:11 AM - Thread Starter
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Yes your steps take me to the same dialog. So then how do I determine the values to enter in each of the 9 boxes for whatever alternate CMF I decide to try?
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post #84 of 89 Old 10-25-2014, 06:35 AM
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post #85 of 89 Old 10-25-2014, 10:02 AM
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^^^^^ See what Zoyd said. I'm assuming you don't have the Spyder4 plugged in? I didn't catch that, sorry for the confusion.

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Originally Posted by robarivas View Post
Yes your steps take me to the same dialog. So then how do I determine the values to enter in each of the 9 boxes for whatever alternate CMF I decide to try?
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post #86 of 89 Old 10-26-2014, 08:54 AM - Thread Starter
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OK, I remember that dialog window now. So does changing the Observer Type automatically take care of changing the reference white point and primaries? Or, in addition to changing the Observer Type, do I also need to go to Preferences-->References--->Color Space and change the white point to Custom and enter the x,y coordinates?

Last edited by robarivas; 10-26-2014 at 09:24 AM.
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post #87 of 89 Old 10-26-2014, 09:54 AM
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You need to change the white point to the custom value given above. Leave the colorspace alone, this is only for grayscale calibration since primaries using the Judd-Vos CMFs are not defined.
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post #88 of 89 Old 10-29-2014, 12:37 PM - Thread Starter
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I'm confused as to whether I should be changing in HCFR the Observer Type, the Color Space / White Point x y coordinates under the Preferences-References menu, or both. Remember, I'm looking for a way to rationally yet "synthetically" achieve the effect of being able to further reduce the blue slider past its minimum setting on all 10 IREs.

Manually (yet somewhat arbitrarily) increasing the white point to a higher color temp (using the correct formula to come up with the x y coordinates) under the Preferences-References menu will work but I'm not sure if this is a legitimate approach.
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post #89 of 89 Old 10-29-2014, 01:17 PM
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The only "legitimate" use of Judd-Vos that I know of is what I said above, change the white point target and use the JV color matching functions for grayscale calibration. This means that a JV observer will see the same color of gray/white as a standard observer using the standard white point. The supposed advantage is that the JV functions are a better match to human perception (primarily in the deep blue) and will give you better perceptual matching of display white points that have narrow primaries. The other stuff you are after I can't help you with.

Last edited by zoyd; 10-29-2014 at 08:17 PM.
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