Need Help on Calibration Mystery - SPECTRAL DATA ADDED - AVS Forum
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post #1 of 29 Old 02-20-2012, 10:24 AM - Thread Starter
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I am desperately in need of some help/sanity. I debated on which forum to post this in but decided this was the most appropriate due to the more technical audience.

The setup:

I have a Sony 55HX929 that I am trying to calibrate. I am using ChromaPure (CP) along with an Xrite i1Display3 (the Pro version with Tom's cal tables) as well as a new (thus freshly calibrated) i1Pro spectro. I also have borrowed a Klein K-10 and double checked white balance using the Klein software. The TV is located in a large room with very pale green walls. I am a lifelong B&W photographer (both film & now digital) with a pretty good background & experience in computer monitor calibration and color theory. I have several Mac computers with calibrated displays using Color Eyes Display Pro (CEDP) software and Datacolor Spyder colorimeters as well as the i1Pro. I also have a DVDO Duo that I am using with the CP autocal for grayscale & gamut. I am calibrating will all of the motion stuff turned off, all of the other post processing turned off and 100% white set very close to 35 fl per SMPTE specs. I am achieving that white point with a backlight of 2 and Picture control of approx 78 - no clipping or color shift noted in the usual patterns. I am using a Color Temp of Warm2.

The problem:

The Sony has a visible green push (easily seen on both gray ramps/step wedges as well as on B&W films) even though the measured white balance with all 3 devices closely aligns to D65 (measured dE < 1). If I tweak the TV WB controls to remove the visible green tint, the measured white point is fairly low on green per the meters.
I have calibrated my MacPro Apple Cinema Display using CEDP and the i1Pro and the resulting gray step wedge is spot on - no detectable color tints. I have calibrated my MacBook Pro display using the Xrite SW and the i1Pro - similar results, although the gray scale tracking is not quite as good.
I am aware of the potential effect on color perception that viewing the TV against a green wall (however pale the color) or in a room with daylight color pollution from reflected light in the room. However, my B&W prints hanging in the room do not appear green and my calibrated laptop does not appear green in the same room. Furthermore, I continue to have a green push even at night with no lights on - in this case the walls appear gray and I can discern no apparent color whatsoever, so it seems the optical illusion of the TV picture taking on the color of the background would not be too likely.
I have gone thru every possible cause for this (me being color blind, TV being defective) but I can't really come up with a plausible explanation other than the spectral response of the TV being considerably different than what the spectro & colorimeters expect. I'm not even sure why the spectro would be fooled by this. I am also not sure how a TV defect could cause this. Since I have seen other mentions of folks successfully having their 929's calibrated, I assume this is not a design artifact due to the panel or backlight.
We are going to paint the room in next month or so (and I'm using a far more neutral color than green of course), but I can't understand what is going on here. I am going to try photographing the screen with a solid gray field using my Nikons with manual daylight WB and see if the resulting images look green on my color managed computer display. I am also considering dragging my old Samsung B7000 into the living room, connecting it to the second Duo output and doing a quick autocal to see if it looks green.
Any ideas on what I could be doing wrong or what on earth could be wrong with this TV that would cause the screen to have a green tint visibly but not measure green?
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post #2 of 29 Old 02-20-2012, 10:52 AM
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No idea since I am new to calibration, but I do have a few questions.

Do you see the green tint in the window patterns when adjusting the gray scale, or only when you display the gradient or ramp of all stimulus at one?

Have you tried changing contrast and back light while displaying the ramp or gradient, does the green remain steady?

Is Local Dimming off as well as all Dynamic anythings?

What stimulus does the green show up in, just the bottom end, just the top, or equally across the range?
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post #3 of 29 Old 02-20-2012, 11:40 AM
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Being that you've been incredibly thorough in your description of the problem, I'm led to believe the issue has more to do with the CIE standard Observer curve from 1931 than it does with anything else.

The method for transforming the visibile spectrum to XYZ which is the basis for all of our other color formulas is called a Color Matching Function. The CMF is responsible for emulating the cones in our eyes and predicting our biological response to any spectral input in a quantitative fashion. This worked very well with CRTs, but as new display technologies have come out with very different spectral outputs than anything in 1931, we are finding that the 1931 CMF is not capable of matching colors from things like LED.

There are a whole host of new CMFs vying to replace the 1931 standard, I'm not in a position to recommend a new CMF at this time, but it's something we are working on.

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post #4 of 29 Old 02-20-2012, 12:03 PM
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Quote:
Originally Posted by khollister View Post

.... The TV is located in a large room with very pale green walls. I am a lifelong B&W photographer (both film & now digital) with a pretty good background & experience in computer monitor calibration and color theory.....

The problem:

The Sony has a visible green push (easily seen on both gray ramps/step wedges as well as on B&W films) even though the measured white balance with all 3 devices closely aligns to D65 (measured dE < 1). If I tweak the TV WB controls to remove the visible green tint, the measured white point is fairly low on green per the meters.......I am aware of the potential effect on color perception that viewing the TV against a green wall (however pale the color) or in a room with daylight color pollution from reflected light in the room. However, my B&W prints hanging in the room do not appear green and my calibrated laptop does not appear green in the same room. Furthermore, I continue to have a green push even at night with no lights on - in this case the walls appear gray and I can discern no apparent color whatsoever, so it seems the optical illusion of the TV picture taking on the color of the background would not be too likely....

The wall color being green would actually subtract green from the TV image perceptually. Of course, the wall would have to be illuminated. This minus green effect would shift a neutral gray image toward magenta in color space.

Best regards and beautiful pictures,
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A Lion AV Consultants affiliate

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post #5 of 29 Old 02-20-2012, 12:03 PM
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The Sony has a visible green push (easily seen on both gray ramps/step wedges as well as on B&W films) even though the measured white balance with all 3 devices closely aligns to D65 (measured dE < 1). If I tweak the TV WB controls to remove the visible green tint, the measured white point is fairly low on green per the meters.

You haven't indicated whether the green tint is seen across all IRE patterns (10-100) or is it reserved for the lower intensity pattern, or higher intensity pattern.

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post #6 of 29 Old 02-20-2012, 12:12 PM - Thread Starter
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Quote:
Originally Posted by bruce View Post

You haven't indicated whether the green tint is seen across all IRE patterns (10-100) or is it reserved for the lower intensity pattern, or higher intensity pattern.

bruce

across the entire range. To answer a question posed earlier, I have tried using different backlight and Picture(contrast) settings with no effect whatsoever. I have left the local dimming on, but can't see what that could possibly do. I'll try it off for grins.

As to whether I see the tint on individual fields versus a ramp or step wedge, I think I do, but for some reason it jumps out far more with content other than a single IRE. That might be significant or might not be.

One other thing I have noticed. an alternating pixel/checkerboard pattern is the fastest indicator of the green tint. this pattern has a far stronger green push than any other type of content. alternating horizontal or vertical lines (or a luminance zone plate) shows nowhere the push that a checkerboard does. Not sure what that says either.
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post #7 of 29 Old 02-20-2012, 12:13 PM - Thread Starter
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Quote:
Originally Posted by GeorgeAB View Post

The wall color being green would actually subtract green from the TV image perceptually. Of course, the wall would have to be illuminated. This minus green effect would shift a neutral gray image toward magenta in color space.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants affiliate

"Advancing the art and science of electronic imaging"

Oops - so I guess we can write that off
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post #8 of 29 Old 02-20-2012, 12:14 PM
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Quote:
Originally Posted by sotti View Post

Being that you've been incredibly thorough in your description of the problem, I'm led to believe the issue has more to do with the CIE standard Observer curve from 1931 than it does with anything else.

The method for transforming the visibile spectrum to XYZ which is the basis for all of our other color formulas is called a Color Matching Function. The CMF is responsible for emulating the cones in our eyes and predicting our biological response to any spectral input in a quantitative fashion. This worked very well with CRTs, but as new display technologies have come out with very different spectral outputs than anything in 1931, we are finding that the 1931 CMF is not capable of matching colors from things like LED.

There are a whole host of new CMFs vying to replace the 1931 standard, I'm not in a position to recommend a new CMF at this time, but it's something we are working on.

I am confused, I thought the observer curve was used with colorimeters, and a spectro would not care one way or another and just read the color and report it? or maybe you are talking about something within the calman program?
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post #9 of 29 Old 02-20-2012, 12:22 PM - Thread Starter
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Quote:
Originally Posted by sotti View Post

Being that you've been incredibly thorough in your description of the problem, I'm led to believe the issue has more to do with the CIE standard Observer curve from 1931 than it does with anything else.

The method for transforming the visibile spectrum to XYZ which is the basis for all of our other color formulas is called a Color Matching Function. The CMF is responsible for emulating the cones in our eyes and predicting our biological response to any spectral input in a quantitative fashion. This worked very well with CRTs, but as new display technologies have come out with very different spectral outputs than anything in 1931, we are finding that the 1931 CMF is not capable of matching colors from things like LED.

There are a whole host of new CMFs vying to replace the 1931 standard, I'm not in a position to recommend a new CMF at this time, but it's something we are working on.

.

While I recognize that the CMF for a wide-gamut LCD might be different from a CRT or PJ, it really doesn't explain why my Apple LCD/LED displays profile perfectly with the same instruments and appear completely neutral. I have 0 display->print matching issues with B&W images.

That would mean (I think) that there is something about the panel in the 929 that has a different spectral output. While I am completely open to that possibility, it would seem that I would have seen others comment on the difficulty in getting a good cal on one of these sets. Not only have I not read that, I have read of several folks claiming their 929's were professionally calibrated with great results.

Granted I don't have access to a Minolta or Photo Research spectro, but I would have thought there would be more of a difference between the i1Pro and the colorimeters. In fact, the Pro seems to measure less green than the D3 or Klein (resulting profile is even more green than that achieved with the D3 Pro from Tom).
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post #10 of 29 Old 02-20-2012, 12:28 PM
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Have you tried a factory reset on the display and then run thought the calibration again?
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post #11 of 29 Old 02-20-2012, 12:30 PM
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As to whether I see the tint on individual fields versus a ramp or step wedge, I think I do, but for some reason it jumps out far more with content other than a single IRE. That might be significant or might not be.

I do remember one of my earlier calibrations of my LED display I noticed a green push and traced it to the fact that on the color clipping pattern (AVS HD709), the green step pattern was clipping at higher levels. The blue and red were OK up to 235, but the green clipped at two or three levels before 235. I had the contrast too high. I redid the calibration of the contrast until it didn't clip, and compensated for the loss in luminance with the backlight. This worked quite well.

I also agree with your idea to test another TV that you feel doesn't 'enjoy' a green push. If it appears green in the 'green room', then your solution is obvious.

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post #12 of 29 Old 02-20-2012, 12:33 PM - Thread Starter
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Quote:
Originally Posted by bruce View Post

I do remember one of my earlier calibrations of my LED display I noticed a green push and traced it to the fact that on the color clipping pattern (AVS HD709), the green step pattern was clipping at higher levels. The blue and red were OK up to 235, but the green clipped at two or three levels before 235. I had the contrast too high. I redid the calibration of the contrast until it didn't clip, and compensated for the loss in luminance with the backlight. This worked quite well.

I also agree with your idea to test another TV that you feel doesn't 'enjoy' a green push. If it appears green in the 'green room', then your solution is obvious.

bruce

Forgot to mention I checked clipping on all three primaries, both with the S&M clipping pattern as well as the one in AVSHD 709. All three channels clip well above 235, and dramatically reducing contrast doesn't help much.

Good suggestion, though
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post #13 of 29 Old 02-20-2012, 12:38 PM - Thread Starter
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Have you tried a factory reset on the display and then run thought the calibration again?

No - I guess I should just for completeness sake, but I can't imagine the physics of how any firmware setting would result in a spectral change (which is the only HW-based reason I can think of that would explain a visual/measured difference).

I have had some extended discussion with a friend of mine here who is a video nut (and fellow electrical engineer), and we can't come up with a manufacturing defect scenario that would account for this. We even considered a registration issue with the filters on the LCD emitters in the Sony panel, but we can't make that hypothesis work either
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post #14 of 29 Old 02-20-2012, 12:46 PM
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I have had some extended discussion with a friend of mine here who is a video nut (and fellow electrical engineer), and we can't come up with a manufacturing defect scenario that would account for this.

Ahh OK, now that I know I'm dealing with fellow engineering types, here's my incredibly technical thesis.

1. Try another TV in the room.

2. Paint the darn room.

hehehe
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post #15 of 29 Old 02-20-2012, 12:57 PM
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Quote:
Originally Posted by khollister View Post

While I recognize that the CMF for a wide-gamut LCD might be different from a CRT or PJ, it really doesn't explain why my Apple LCD/LED displays profile perfectly with the same instruments and appear completely neutral. I have 0 display->print matching issues with B&W images.

CMFs are different from SPD (Spectral distributions). The Klien and the i1 Display 3 are essentially hardware implementations of the CMF. A CMF is suppose to work on everything, it matches the colors colors from different spectral outputs. We've seen in our Lab that even white LEDs can be substantially different from each other.

Quote:
Originally Posted by khollister View Post

That would mean (I think) that there is something about the panel in the 929 that has a different spectral output. While I am completely open to that possibility, it would seem that I would have seen others comment on the difficulty in getting a good cal on one of these sets. Not only have I not read that, I have read of several folks claiming their 929's were professionally calibrated with great results.

I would bet that those customers don't have the trained eye that you have. If an i1 Pro is reading that a color is D65, it's almost assuredly very very close to D65. My assertion is that among the infinite variety of SPDs that produce D65, any light source that has alot of near-ultraviolet energy is going to produce a D65 that is visibly green using the 1931 Standard Observer CMF.

I don't know if chromapure can do spectrum readings so you can view what the spectrum looks like, but compare how different the apple LCD and the sony are.

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post #16 of 29 Old 02-20-2012, 01:17 PM - Thread Starter
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Quote:
Originally Posted by sotti View Post

CMFs are different from SPD (Spectral distributions). The Klien and the i1 Display 3 are essentially hardware implementations of the CMF. A CMF is suppose to work on everything, it matches the colors colors from different spectral outputs. We've seen in our Lab that even white LEDs can be substantially different from each other.



I would bet that those customers don't have the trained eye that you have. If an i1 Pro is reading that a color is D65, it's almost assuredly very very close to D65. My assertion is that among the infinite variety of SPDs that produce D65, any light source that has alot of near-ultraviolet energy is going to produce a D65 that is visibly green using the 1931 Standard Observer CMF.

I don't know if chromapure can do spectrum readings so you can view what the spectrum looks like, but compare how different the apple LCD and the sony are.

Aha - now that makes sense. While it is possible that some of the end users might not notice, I find it hard to believe that someone like Chad or Dnice wouldn't see this (assuming they have cal'ed a 929). While fairly subtle on color material that you are not intimately familiar with, it is pretty obvious on B&W content IMHO.

My friend with the Klein said he had a program someone had done a while back that pulled the raw data for the 128 bins of the i1Pro so you could see the spectral distribution. He is going to try and find it this evening.
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post #17 of 29 Old 02-20-2012, 01:41 PM
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Had another thought, you didn't say if you used windows or full fields when you did the gray scale. Try the opposite of what you used.. should not matter on LCD or so they say.. but can't hurt to try.
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post #18 of 29 Old 02-20-2012, 01:46 PM
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Sort of off topic but has the variation in color perception (if that is the correct word) from person to person been studied?

I know that my right eye sees color noticeably different from my left eye - the world is a "warmer" place using my right eye.

So I assume that person to person variation my be substantial.

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post #19 of 29 Old 02-20-2012, 02:11 PM
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Originally Posted by fcwilt View Post

Sort of off topic but has the variation in color perception (if that is the correct word) from person to person been studied?

I know that my right eye sees color noticeably different from my left eye - the world is a "warmer" place using my right eye.

So I assume that person to person variation my be substantial.

Has, is, and will continue to be studied around the world.

Assume nothing. Get the facts.
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post #20 of 29 Old 02-20-2012, 02:21 PM
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Originally Posted by GeorgeAB View Post

Has, is, and will continue to be studied around the world.

Assume nothing. Get the facts.

Studies I've seen can report up to a measured dE difference of 4 (dE 76 Lab) between different subjects perception. Because there are real differences in the sensitivity of individual eyes, the primary goal of a Color Matching Funciton can't be to eliminate the error, but to minimize and center the error.

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post #21 of 29 Old 02-20-2012, 03:29 PM
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"Granted I don't have access to a Minolta or Photo Research spectro, but I would have thought there would be more of a difference between the i1Pro and the colorimeters. In fact, the Pro seems to measure less green than the D3 or Klein (resulting profile is even more green than that achieved with the D3 Pro from Tom). "

I have a Minolta CL-200 & I live in Orlando.
If you need to use it,let me know.

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Originally Posted by Beta-Boy View Post

"Granted I don't have access to a Minolta or Photo Research spectro, but I would have thought there would be more of a difference between the i1Pro and the colorimeters. In fact, the Pro seems to measure less green than the D3 or Klein (resulting profile is even more green than that achieved with the D3 Pro from Tom). "

I have a Minolta CL-200 & I live in Orlando.
If you need to use it,let me know.

Bruce

The CL-200 is just a colorimeter, the Klein K-10 exceeds the CL-200's specifications.

I think he was thinking more about a CS-200, CS-1000 or CS-2000.

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post #23 of 29 Old 02-20-2012, 03:58 PM - Thread Starter
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The CL-200 is just a colorimeter, the Klein K-10 exceeds the CL-200's specifications.

I think he was thinking more about a CS-200, CS-1000 or CS-2000.

Exactly, but mucho thanks to Beta Boy for the offer anyway
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Quote:
Originally Posted by khollister View Post


My friend with the Klein said he had a program someone had done a while back that pulled the raw data for the 128 bins of the i1Pro so you could see the spectral distribution. He is going to try and find it this evening.

perhaps he was referring to Argyll CMS:

spotread -d -x -N -s -S -H

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post #25 of 29 Old 02-21-2012, 04:08 AM - Thread Starter
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Quote:
Originally Posted by turbe View Post

perhaps he was referring to Argyll CMS:

spotread -d -x -N -s -S -H

that is exactly what he was referring to - he sent me the link last night. I will try and get this running in the next day or so and see what I get.
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post #26 of 29 Old 02-21-2012, 03:24 PM - Thread Starter
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OK - measured the Apple Cinema Display with a i1Pro-based cal profile and the Sony 929 with a i1Pro "calibrated" grayscale - both with a full screen 50IRE pattern from AVSHD 709.

The spectral plots from ArgyllCMS are below - first is ACD, second is Sony HX929. While the blue peak is higher in frequency on the Sony (longer wavelength), this doesn't seem like enough SPD difference to account for Joel's near-UV/CMF green shift theory.

What do you guys think?

Apple 27" Cinema Display:


Sony 55HX929 TV:
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post #27 of 29 Old 02-21-2012, 03:35 PM
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Can you put up that data in csv or excel?

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post #28 of 29 Old 02-21-2012, 04:04 PM - Thread Starter
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Quote:
Originally Posted by sotti View Post

Can you put up that data in csv or excel?

Hmm - I just grabbed the plots from Argyll. It prints out the xyY data in the terminal window (I'm running this on my MacBook Pro in OS X), so I need to think of how to do that. I think there might be a command line option to dump the measured data to a file. I'll give it another try after dinner.

However, another important data point. I had my wife (who sews and draws - creative type, visually oriented) look at a gray ramp on the Sony with the "measures flat" profile. I asked her if she saw a color tint - the answer was no (I see a slight green push, especially above 50IRE). I then cranked in my WB adjustments to pull the green out (which looks fairly neutral gray to me) and asked her what she saw - immediate response was pink!.

Went back to my MacPro and ACD. Put up a gray ramp full screen as well as a B&W image (this is using my latest ICC monitor profile made with the same i1Pro) - we both see neutral gray !

Clearly there is something about the Sony TV or the environment it is in that is interacting with my vision differently. BTW, I did the TV test with all the lights off, so the walls in the room are pretty devoid of color visually.

So I see there are 2 possibilities:

1) however slight the spectral shift is in the TV, it is enough to have my vision react differently with respect to color perception

2) There is enough green light being bounced around in the room from the TV screen on the green walls to skew my color perception. I do have pretty good night vision in spite of my age (57), so maybe I have some particularly sensitive cones that are still active where most people have shifted to rods (monochromatic). I could swear the green shift IS more visible to me during the day, so maybe painting the room will make all of this go away.

Color me confused (pun intended)
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post #29 of 29 Old 02-21-2012, 06:42 PM
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So I see there are 2 possibilities

3rd possibility: medication.

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