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AVIA saturation vs color decoder problem

post #1 of 31
1/8/07 at 11:08am
Thread Starter 
I have a question for those familiar with the popular Avia calibration DVD:

Background: I own a Panasonic TH-42PX600U plasma TV and a Sony upscalling DVD player, hooked up via HDMI to the TV.

- When setting the color saturation (equal blue between the top and bottom rectangles), using the blue filter, I'm able to set the color saturation and tint quite easily. My color setting ends up being -4 and the tint -4 also. With these settings, everything is of equal blue, and I can not really notice the flashing patches.

However, on the next test, "Color Decoder Check", I use the blue/red/green fliters to check the color decoder accuracy, and the result is weird:

-10% red
-10% green
-15% blue

My questions is: how can the saturation be set perfectly (in the color/hue test), and yet this next test tells me everything is "under-saturated" by 10% or more?

If I increase my color setting from -4 to about -1, the color decoder check reads 0% for red/green/blue (perfect!), but if I go back to the color/hue test, it tells me my colors are over-saturated (blue rectangles are no longer equal in brightness).

Any clue why this is happening? Why don't both tests corroborate each other? Which test result should be trusted most? Color/hue or Color Decoder Check? Whats better: having the color saturation set perfect in the color/tint test OR 0% push/pull for all colors in the colors decoder check?

I'm confused

Thanks!
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post #2 of 31
1/8/07 at 11:32am
It's common for displays to have red and/or green color decoding errors after setting the color and tint using blue. I'm not sure why you also see an error in blue; I use Avia frequently and I've never seen this.

FYI, Avia also has color bars with flashing patches for green and red.

-Steve
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post #3 of 31
1/8/07 at 11:35am
Thread Starter 
Quote:
Originally Posted by slb View Post

It's common for displays to have red and/or green color decoding errors after setting the color and tint using blue. I'm not sure why you also see an error in blue; I use Avia frequently and I've never seen this.

-Steve

Hence the weirdness of this particular calibration. I have also calibrated many displays with Avia and have never seen this before. Very strange. At the very least, I would have expected the blue to read 0% after setting color/tint, but no.

As I mentionned, the color decoder in the panny seems very good, as I can bring them all (red/green/blue) to exactly 0% when my color setting reads -1. The problem then is that my color saturation is way out of whack..
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post #4 of 31
1/8/07 at 11:41am
Thread Starter 
Quote:
Originally Posted by slb View Post

FYI, Avia also has color bars with flashing patches for green and red.

Really? Where? I never noticed it before. And would using the red or green filter with patches be more accurate than the blue?
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post #5 of 31
1/8/07 at 12:06pm
The color decoder check tells you if the decoder is emphasizing/deemphasizing each color. It doesn't serve quite the same function as the blue color bars, which allow you to balance the color decoder's intensity and phase. Look at the green and red bars through the filters. They will appear monotone red or green (just as the blue bars should) only if your decoder is properly aligned. Better yet, if your display allows you to turn off individual colors, use that to do the color bars and decoder check. Filters can leak other colors of light and do change over time, so isolating colors in the display is the more accurate method.
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post #6 of 31
1/8/07 at 12:27pm
Thread Starter 
Quote:
Originally Posted by Rolls-Royce View Post

The color decoder check tells you if the decoder is emphasizing/deemphasizing each color. It doesn't serve quite the same function as the blue color bars, which allow you to balance the color decoder's intensity and phase. Look at the green and red bars through the filters. They will appear monotone red or green (just as the blue bars should) only if your decoder is properly aligned. Better yet, if your display allows you to turn off individual colors, use that to do the color bars and decoder check. Filters can leak other colors of light and do change over time, so isolating colors in the display is the more accurate method.

Thanks for your input Rolls-Royce. However, I'm not sure how this solves my problem. I am aware that the color/hue test serves a different purpose than the color decoder check, and I do know about the light leakage and filter degradation over time. However, my blue plastic filter, whether degraded or not, is the same filter for both tests and, normally (unless an AVIA specialist comes in here and proves me wrong), if used correctly, the color setting I should end up with, after the color/hue test, should be quite near the 0% (for blue) in the color decoder check, and there could be small differences with red and/or green. However, in this particular case, it is not

Even worse, in the CDC test, ALL my colors read negative % once my color/tint has been set properly in the previous test. How can the colors be saturated just right, but yet all read "under-driven" im the CDC test??

So, I'm asking again: whats better? having all colors read 0% in the decoder check OR (since I can't seem to have both in this case) matching blue brightness in the color/tint test and patches that don't flash?
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post #7 of 31
1/8/07 at 1:10pm
Just a thought; Make sure you have turned off any "color management" settings that your display has. These can dynamically adjust color saturation depending on the picture content.

-Steve
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post #8 of 31
1/8/07 at 6:15pm
Thread Starter 
Quote:
Originally Posted by slb View Post

Just a thought; Make sure you have turned off any "color management" settings that your display has. These can dynamically adjust color saturation depending on the picture content.

-Steve

Yep. I thought about this and disabled the Color Management option in the menu. Not much changed.
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post #9 of 31
1/8/07 at 10:23pm
If you align blue on the colorbars, it should read 0% on the color decoder test. The color decoder test can be a little difficult to read sometimes, I would trust the flashing bars more because the flashing makes these things more easily visible. I don't know why blue would be off on the push pattern but okay on the colorbars, this does not make sense since they are basically the same thing, they should appear the same. Which is why I suggest the human-error difficulty in terms of reading the push pattern.
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post #10 of 31
1/9/07 at 3:57am
Thread Starter 
Quote:
Originally Posted by ChrisWiggles View Post

If you align blue on the colorbars, it should read 0% on the color decoder test. The color decoder test can be a little difficult to read sometimes, I would trust the flashing bars more because the flashing makes these things more easily visible. I don't know why blue would be off on the push pattern but okay on the colorbars, this does not make sense since they are basically the same thing, they should appear the same. Which is why I suggest the human-error difficulty in terms of reading the push pattern.

Thanks Chris.

This is why this whole situation baffles me too. I used Avia many times in the past to calibrate displays, and never had this sort of problem before. The panny plasmas are known to have pretty accurate colors. This is my 2nd panasonic plasma tv in my household, and the 1st one was easy to calibrate last year.

I can't say why both tests are not in sync. And not only the blue.. The red and green in the color decoder are also off, in comparison with the perfect saturation/no flashing patches of the color/tint test...

In any case, if you recommend trusting the color/tint test more, this is what I will do and I'll simply disregard the color decoder check test.

Still, I'd very much like to find what is causing this difference.

One thing I was wondering, and maybe someone here can answer this:

I have, obviously, a 16:9 display. My DVD player is also set to 16:9. And the panny is set to the "full" aspect ratio for the DVD/HDMI input. Therefore, the Avia calibration DVD plays in "full screen". However, isn't the Avia DVD authored in 4:3? Would it make a difference if I set my aspect ratio to 4:3 on the plasma, and calibrate the set this way, instead of "stretched to full"? Would the results be any different?

Also, my DVD player has a setting for colors thats says: CbPb or RGB. Mine is set to CrPb (spell?). Should it be set to RGB? I tried both settings when playing a regular DVD and did not really see a difference.

Thanks
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post #11 of 31
1/9/07 at 10:28am
Quote:
Originally Posted by stripe1 View Post

In any case, if you recommend trusting the color/tint test more, this is what I will do and I'll simply disregard the color decoder check test.

FWIW, I pulled out my copy of AVIA last night and did a quick (filter based) evaluation on my CRT RPTV. Results: even using two "stacked" blue filters, I was unable to get any conclusive results from the "decoder check" screen. OTOH, the color bars were easy to evaluate. I certainly would not attempt to use the "decoder check" screen to set my color/tint controls.
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post #12 of 31
1/9/07 at 11:00am
On a related subject, since the human eye is much more sensitive to red than blue, wouldn't it be a better approach to set saturation/hue using the Avia red color bars and red filter than using the blue color bars and blue filter? I would think that any resulting errors in blue would be more acceptable than the errors in red that often occur after setting saturation/hue with the blue filter/bars approach.

What's wrong my thinking on this?
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post #13 of 31
1/9/07 at 11:53am
Quote:
Originally Posted by TomHuffman View Post

On a related subject, since the human eye is much more sensitive to red than blue, wouldn't it be a better approach to set saturation/hue using the Avia red color bars and red filter than using the blue color bars and blue filter? I would think that any resulting errors in blue would be more acceptable than the errors in red that often occur after setting saturation/hue with the blue filter/bars approach.

What's wrong my thinking on this?

Unfortunately, manufacturers are notorious for adjusting their displays to decode red incorrectly. They often push red to help offset the fact that the display's default color temperature is set too high. In these cases, if you adjust using red, blue and green may be severely undersaturated.

-Steve
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post #14 of 31
1/9/07 at 12:13pm
So, you guys recommend I stick with the Blue filter and blue bars to set color/hue correctly, and disregard the color decoder test? And what about the setting for CrCbPr or RGB in the DVD player?
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post #15 of 31
1/9/07 at 12:17pm
Quote:
Originally Posted by slb View Post

Unfortunately, manufacturers are notorious for adjusting their displays to decode red incorrectly. They often push red to help offset the fact that the display's default color temperature is set too high. In these cases, if you adjust using red, blue and green may be severely undersaturated.

-Steve

Apparently, human eyes better tolerate normal reds and less saturated greens and blues, rather than normal green and blue, but oversaturated red. Therefore, would it not make sense to adjust colors using the red bars, instead of the blue bars, therefore making sure that red is not oversaturated (even is that means that blue and green is a bit less saturated)?
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post #16 of 31
1/9/07 at 12:18pm
This is certainly true, but for the reasons I mentioned in cases where you can't adjust the color decoder (if you can, then this won't be an issue) isn't the recommended approach to lower overall saturation, thereby undersaturating blue and green anyway. In other words, isn't an undersaturated blue and green preferable to an oversaturated red?

Quote:
Originally Posted by slb View Post

Unfortunately, manufacturers are notorious for adjusting their displays to decode red incorrectly. They often push red to help offset the fact that the display's default color temperature is set too high. In these cases, if you adjust using red, blue and green may be severely undersaturated.

-Steve
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post #17 of 31
1/9/07 at 12:21pm
Quote:
Originally Posted by TomHuffman View Post

in other words, isn't an undersaturated blue and green preferable to an oversaturated red?

Exactly, as I also pointed out in the above post.

This is why I think that it makes more sense to adjust color saturation using the red filter, instead of blue, to make sure that red is not oversaturated, regardless of where blue and green end up in the scale.

Can I use Avia and a red filter to adjust color saturation? If so, how? I only know how to do it with the blue and white rectangles. It would be the same thing, but using a red bar + a white box?
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post #18 of 31
1/9/07 at 12:42pm
Quote:
Originally Posted by stripe View Post

Exactly, as I also pointed out in the above post.

This is why I think that it makes more sense to adjust color saturation using the red filter, instead of blue, to make sure that red is not oversaturated, regardless of where blue and green end up in the scale.

Can I use Avia and a red filter to adjust color saturation? If so, how? I only know how to do it with the blue and white rectangles. It would be the same thing, but using a red bar + a white box?


It would depend on how far off red is. Some manufacturers boost red by as much as 25%. That means setting red to be correct would under-saturate green and blue by 25%, which could have a much more detrimental effect on your color gamut than just having a red error.

The traditional approach would be to desaturate green and blue a bit to get red within 15% of correct. Most displays these days are not as bad as they were a just few years ago.

If the color decoding is corrrect, you can use any of the primaries to set tint (hue) and color (saturation). The process is the same as for blue. Using standard color bars and red filter, you adjust the settings until the red, magenta, yellow and gray bars are all the same. For green, you focus on the green, cyan, yellow and gray bars.

Also, Avia has color bars with flashing patches for green and red. These can be found in the advanced menu.

-Steve
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post #19 of 31
1/9/07 at 1:06pm
Thx Steve, I'll give those a shot tonight.
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post #20 of 31
1/12/07 at 9:36am
So, I did try to calibrate the tv's saturation using the blue, red, and green bars in AVIA. But, whatever I do to get the satuation just right (calibrating using any of the 3 primaries yeilds similar results), the color decoder check still reads approx. -10% on all three colors.

I still can't figure out why that is.
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post #21 of 31
1/12/07 at 10:16am
Strange, but at this point I would probably ignore it. The color decoder check is provided to help identify color decoding errors where one or more colors exhibit significantly different saturation levels than the color used for calibration. If the standard color bars basically look correct for all three colors when viewed through the filters, then I think everything is okay.

-Steve
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post #22 of 31
1/12/07 at 10:29am
I think you are right, and I'll just have to live with it
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post #23 of 31
1/15/07 at 6:07am
Quote:
Originally Posted by stripe1 View Post

- When setting the color saturation (equal blue between the top and bottom rectangles), using the blue filter, I'm able to set the color saturation and tint quite easily. My color setting ends up being -4 and the tint -4 also. With these settings, everything is of equal blue, and I can not really notice the flashing patches.

However, on the next test, "Color Decoder Check", I use the blue/red/green fliters to check the color decoder accuracy, and the result is weird:

-10% red
-10% green
-15% blue

I hit exactly the same problem over the weekend on my neighbors LG 37" LCD. Weird.

I'm wondering is upping the saturation will increase the values on the "Color Decoder CHeck" screen for all three bars? I'll need to go back and see if the colors look a little washed out.

jdg
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post #24 of 31
1/15/07 at 10:08am
Consider the possibility that the gray background on the color decoder check may be @ 100% (vs ~75% for the standard SMPTE color-bar patterns.)

The bottom line is that regardless of the actual numbers you are seeing, all three colors are within 5% of each other ... thus there is minimal (if any) "push" being applied by your color decoder. ... And that is all this pattern was ever meant to measure. Relax, drive on down the road.
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post #25 of 31
1/23/07 at 6:04pm
Should this test work properly only if grayscale is properly calibrated (to D65 I believe)? I guess, only in this case gray would contain the same amount of blue as blue, or do I not understand something?
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post #26 of 31
1/23/07 at 9:50pm
You can adjust the CMY without grayscale being correct - but the tints will not be correct unless the grayscale is correct.

You are correct if white has the wrong amount of blue - so will your cyan/magenta even though that results in the color decoder aligned. RGB does not depend on a proper D65 - but D65 depends on RGB mixture. So yes I think your RGB decoding pattern will depend on D65 - let me think some more on that interaction though....
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post #27 of 31
1/23/07 at 10:28pm
You do not need a correct or even a functioning grayscale to align color decoding. Of course, with grayscale off, then *everything* is going to be wrong including your colors, but color decoding will still be aligned correctly.
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post #28 of 31
1/23/07 at 10:36pm
I don't think my post made any sense...

When using the blue filter - your color decoder is correct when BCMW match each other.

likewise for red, and green with their filtered gamuts...

What I meant to say is the resulting colors will not measure correct in terms of CIE xyY even if the filters say the color decoder is aligned but the greyscale is not D65.

Makes sense?
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post #29 of 31
1/23/07 at 11:10pm
Kras, it's late, go get some rest. you're still not making too much sense!

What Kras is trying to say is that when using the blue filter, you can align the color decoding, but that the actual colors you get on the screen is the product of BOTH accurate color decoding AND accurate grayscale. so, if grayscale is bonkers, then the actual colors you get will be bonkers, especially the secondaries, even if color decoding is properly aligned.

Grayscale affects everything, including color. Color decoding ONLY affects color. If you get color decoding right, you can still have totally messed up colors if grayscale is off.

But greyscale does not affect color decoding alignment.

Okay, now I'm starting to sound confusing like Kras! It's a confusing topic...

hope that helps!
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post #30 of 31
1/24/07 at 8:38am
To further confuse the situation:

The way the color decoder check pattern was meant to be used is:

0) Using the SMPTE Color Bar based patterns, properly adjust your color and tint controls.

1) Now display the "Color Decoder Check" pattern.

2) Pick a color (Blue works best)

3) Using the appropriate filter (i.e. blue,) adjust your color/saturation control so that you get 0% on that color's scale.

4) Using the other two filters, read the approximate % that each is pushed or pulled.

5) If you changed your color/saturation in step three, return it to it's original setting (derived from the SMPTE Color Bar patterns.)

Note1: Due to excessive filter leakage, green will always appear significantly "pulled" (low) when using this filter method.

Note2: This pattern was *never* intended to set the final color/tint setting, in fact it is completely useless for tint. Use the traditional SMPTE color-bar patterns instead.
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