LCD White Clipping Test Pattern - AVS Forum
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post #1 of 23 Old 01-02-2012, 05:13 PM - Thread Starter
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In the past I was unable to set the "Picture" setting on my NX720 high enough to come just short of clipping whites. I had the Picture at Max and the WTW bars were still blinking.

Today I found the way to adjust the RG&B gains in the Service Mode. I increased them high enough to them to be able to set the Picture to be just short of clipping white. I was also able to avoid any of the primaries running out and causing a color shift (at least to my eye).

So, would there be any ill effect of doing this in the Service Mode?
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post #2 of 23 Old 01-02-2012, 06:42 PM - Thread Starter
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Originally Posted by snash22 View Post

In the past I was unable to set the "Picture" setting on my NX720 high enough to come just short of clipping whites. I had the Picture at Max and the WTW bars were still blinking.

Today I found the way to adjust the RG&B gains in the Service Mode. I increased them high enough to them to be able to set the Picture to be just short of clipping white. I was also able to avoid any of the primaries running out and causing a color shift (at least to my eye).

So, would there be any ill effect of doing this in the Service Mode?

Also, is it important to have it set to just short of clipping?
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post #3 of 23 Old 01-02-2012, 07:00 PM
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Greetings

Follow the 3 rules to setting contrast.

The link in my sig leads to articles that explain this and much more.

regards

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post #4 of 23 Old 01-02-2012, 08:14 PM - Thread Starter
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Originally Posted by Michael TLV View Post

Greetings

Follow the 3 rules to setting contrast.

The link in my sig leads to articles that explain this and much more.

regards

Hmmm, don't see any links in your sig...
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post #5 of 23 Old 01-03-2012, 12:22 AM
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You don't want Contrast set just short of clipping unless the TV clips at REALLY low light output levels (not very common). All the test patterns tell you is how to find the HIGHEST possible setting you should ever use for Contrast. Most of them keep repeating that same procedure because in the days of CRT displays you almost always wanted to find the highest possible Contrast setting. Today, some displays NEVER clip white no matter what you do. Put the Gain settings back where they were and forget about adjusting them unless you have a meter and calibration software.

You want about 35 fL (plus or minus a little) for watching TV in a dark room... your TV might produce 70 or 90 or maybe even more than 100 fL with Contrast set to the highest. Without a meter, you have no idea how bright the panel is and all you can really do is see if the Contrast level you are using causes eyestrain or squinting. If you detect either while watching the TV in a dark toom, keep reducing Contrast until the squinting or eyestrain feeling stops... it might take 15 minutes to 2 hours for the eyestrain to be noticeable.

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post #6 of 23 Old 01-03-2012, 10:57 AM
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Originally Posted by snash22 View Post

So, would there be any ill effect of doing this in the Service Mode?

My Sony SXRD can likewise have contrast turned higher in the service menu, and it will generally pass a clipping test, but doing so causes gamma and color shift problems when measured. Without more information, such as measurements, I would suggest it may not be a good idea to turn contrast higher than Sony intended.


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post #7 of 23 Old 01-04-2012, 04:18 PM - Thread Starter
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Although I understand the hazards of the eye being fooled by not using a meter, I am curious as to whether clipping WTW is desirable or not.

If it is, I'll consider whether to purchase a meter based on the answer (and the cost).

I haven't had any issues with eyestrain, even after last night's 3 hour Dexter marathon
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post #8 of 23 Old 01-04-2012, 04:50 PM
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Quote:
Originally Posted by snash22 View Post

Although I understand the hazards of the eye being fooled by not using a meter, I am curious as to whether clipping WTW is desirable or not.

If it is, I'll consider whether to purchase a meter based on the answer (and the cost).

I haven't had any issues with eyestrain, even after last night's 3 hour Dexter marathon

Clipping WTW is not desirable. You'd only want to do so if the only way to get sufficient light output from a display was to sacrifice some of the range past 235 to 254. This could occur on a Plasma or CRT display that has no backlight setting. LCD/LED can use the backlight setting to compensate for having to turn down contrast significantly to avoid clipping WTW.

In your case, you could leave user contrast at max (100%) but leave the SM settings at their defaults.


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post #9 of 23 Old 01-04-2012, 05:48 PM - Thread Starter
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Originally Posted by PlasmaPZ80U View Post


Clipping WTW is not desirable. You'd only want to do so if the only way to get sufficient light output from a display was to sacrifice some of the range past 235 to 254. This could occur on a Plasma or CRT display that has no backlight setting. LCD/LED can use the backlight setting to compensate for having to turn down contrast significantly to avoid clipping WTW.

In your case, you could leave user contrast at max (100%) but leave the SM settings at their defaults.

Ok, so you refer to clipping WTW as "sacrificing some of the range past 235...".

Are you inferring that that range is desirable to keep?
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post #10 of 23 Old 01-04-2012, 06:52 PM - Thread Starter
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Originally Posted by snash22 View Post


Ok, so you refer to clipping WTW as "sacrificing some of the range past 235...".

Are you inferring that that range is desirable to keep?

Ok, blue shirt guy in the rev3 video says there could be detail in there, so go ahead and keep it. Is that alluringreality?

Good enough for me. I'll go back and reset the SM gain settings.
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post #11 of 23 Old 01-05-2012, 01:31 AM
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Quote:
Originally Posted by snash22 View Post

Although I understand the hazards of the eye being fooled by not using a meter, I am curious as to whether clipping WTW is desirable or not.

If it is, I'll consider whether to purchase a meter based on the answer (and the cost).

I haven't had any issues with eyestrain, even after last night's 3 hour Dexter marathon

First sentance illustrates the dilemma I am curious to understand.

Seemingly it is part of the technical process to design and use algorithms for color space choices that use the adaptability of the human eye, together with displays that are designed to also use this feature.

My question is this, who decides when technical accuracy overides eyesight as a right / wrong of PQ?
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post #12 of 23 Old 01-05-2012, 06:13 AM - Thread Starter
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Originally Posted by PE06MCG View Post

First sentance illustrates the dilemma I am curious to understand.

Seemingly it is part of the technical process to design and use algorithms for color space choices that use the adaptability of the human eye, together with displays that are designed to also use this feature.

My question is this, who decides when technical accuracy overides eyesight as a right / wrong of PQ?

I think that the idea is for everyone to agree to a specific standard, so that when a video goes through the chain from the camera to your set everyone is using the same assumptions about what color white is.
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post #13 of 23 Old 01-05-2012, 07:05 AM
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Originally Posted by snash22 View Post

I think that the idea is for everyone to agree to a specific standard, so that when a video goes through the chain from the camera to your set everyone is using the same assumptions about what color white is.

Can't argue with standards, they have been arrived at with presumably the human eyes frailties in mind.

So from then on we have to assume all calibration should have 'visible perception' via the human eye in mind, after all the standards we use base their existance on our visual perception capability.

I suppose my real question is why does the subsequent calibration process often strive to correct non visible meter errors?

Apologies if my lack of technical knowledge prevents correct terminology.
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post #14 of 23 Old 01-05-2012, 07:36 AM
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I suppose my real question is why does the subsequent calibration process often strive to correct non visible meter errors?

Apologies if my lack of technical knowledge prevents correct terminology.

Because the obsessive compulsive perfection personality traits that we all have tell us that 0 error is better than .6 error.. even though we can not see it, we feel the need to fix it..

Doug

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post #15 of 23 Old 01-05-2012, 12:18 PM
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I don't understand why whiter than white would influence a meter purchase in any way. Whiter than white has nothing to do with anything you need a meter for. You calibrate displays that don't display whiter than white the same way you calibrate displays that do show whiter-than-white.

The value of whiter-than-white is probably overstated. Over the years I've reviewed several displays that didn't show whiter-than-white and the picture was not noticeably compromised. Primarily because whiter-than-white pixels tend to be somewhat randomly distributed and they don't make up large objects or areas. 100% white is the reference level and pixels above 100% white exist only for "headroom" that allows for some "overage" without clipping everything to the same level. Where to whiter-than-white pixels appear? Primarily in what is called spectral highlights... these encompass, most often, bright reflections from chrome or a crystal chandelier or sun reflecting on the surface of water, etc. If the display clips at 100% white (235), there's really no image information lost and those strongly reflected highlight still look appropriately bright if 235 is the highest white level the display shows.

BUT... white levels of 101%-109% (236-254) are "legal" and they do appear in many movies and if the TV will resolve levels above 100% you shouldn't adjust it so that the steps above 100%/235 disappear. If the TV doesn't show levels above 100%/235 it's not the end of the world and will ultimately have little or no visible repercussions.

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post #16 of 23 Old 01-05-2012, 12:29 PM
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Quote:
Originally Posted by Doug Blackburn View Post

I don't understand why whiter than white would influence a meter purchase in any way. Whiter than white has nothing to do with anything you need a meter for. You calibrate displays that don't display whiter than white the same way you calibrate displays that do show whiter-than-white.

The value of whiter-than-white is probably overstated. Over the years I've reviewed several displays that didn't show whiter-than-white and the picture was not noticeably compromised. Primarily because whiter-than-white pixels tend to be somewhat randomly distributed and they don't make up large objects or areas. 100% white is the reference level and pixels above 100% white exist only for "headroom" that allows for some "overage" without clipping everything to the same level. Where to whiter-than-white pixels appear? Primarily in what is called spectral highlights... these encompass, most often, bright reflections from chrome or a crystal chandelier or sun reflecting on the surface of water, etc. If the display clips at 100% white (235), there's really no image information lost and those strongly reflected highlight still look appropriately bright if 235 is the highest white level the display shows.

BUT... white levels of 101%-109% (236-254) are "legal" and they do appear in many movies and if the TV will resolve levels above 100% you shouldn't adjust it so that the steps above 100%/235 disappear. If the TV doesn't show levels above 100%/235 it's not the end of the world and will ultimately have little or no visible repercussions.

This is the answer to the OP's original question and also what many have suggested or said.


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post #17 of 23 Old 01-05-2012, 05:25 PM
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Originally Posted by snash22 View Post

Ok, blue shirt guy in the rev3 video says there could be detail in there, so go ahead and keep it. Is that alluringreality?

I'm not aware of anyone actually documenting above-white information in mainstream commercial video material that clearly originated from the source. While the standards do allow excursion beyond reference white, most of the above white information I've looked at (DVD, Blu-ray, OTA ATSC) appears to likely result from the process of delivering video, rather than obviously coming from photographed information. Based on the video I've looked at, I consider it highly questionable if there's any real above white detail in most commercial video, so personally I don't put importance on ideal reproduction of above white information.

What I was getting at is that if you only focus on where gray appears to clip near white you may miss other display changes as you increase contrast. For example some digital displays tend to clip red, green, and blue in the grayscale at slightly different levels, so you will often get some color shift near where the display appears to clip white. At a lower contrast setting such a color shift might primarily appear above reference white, but by increasing contrast the color shift may happen at reference white. I'm not sure how many displays change gamma near white clipping, but when using the service menu controls my TV drops gamma enough for a noticeable change between 95% and 100% gray bars. I was mainly pointing out that on my Sony there seems to be some reasoning for where they set the maximum picture setting.


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post #18 of 23 Old 01-06-2012, 07:55 AM - Thread Starter
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Originally Posted by Doug Blackburn View Post

I don't understand why whiter than white would influence a meter purchase in any way. Whiter than white has nothing to do with anything you need a meter for.

I was only discussing getting a meter if in fact WTW was something I *did* want to get rid of. The meter would help to make sure I didn't screw up the colors in the normal range when eliminating the WTW.
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post #19 of 23 Old 01-06-2012, 08:05 AM - Thread Starter
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BUT... white levels of 101%-109% (236-254) are "legal" and they do appear in many movies and if the TV will resolve levels above 100% you shouldn't adjust it so that the steps above 100%/235 disappear. If the TV doesn't show levels above 100%/235 it's not the end of the world and will ultimately have little or no visible repercussions.

Quote:
Originally Posted by PlasmaPZ80U View Post

This is the answer to the OP's original question and also what many have suggested or said.

The three types of responses to my original question were as follows.

1. Don't do it, you'll screw up colors elsewhere.
2. Don't do it, you need a meter to do it right.
3. Don't do it, WTW is OK, maybe even good to have.

Although number 1 & 2 are accurate, it was number 3 that I needed to know and was not in the original responses. That is why I kept at it, sorry if I was a pain here, just trying to learn
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post #20 of 23 Old 01-07-2012, 11:04 AM
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Originally Posted by snash22 View Post

The three types of responses to my original question were as follows.

1. Don't do it, you'll screw up colors elsewhere.
2. Don't do it, you need a meter to do it right.
3. Don't do it, WTW is OK, maybe even good to have.

Although number 1 & 2 are accurate, it was number 3 that I needed to know and was not in the original responses. That is why I kept at it, sorry if I was a pain here, just trying to learn

This still indicates you don't understand the issue because none of those 3 "condensations" are right. If the TV shows WTW, the color is probably already screwed up because it hasn't been calibrated. So futzing with the controls that affect whether WTW is visible or not could make the color of white BETTER or WORSE... and you won't know which without a meter.

#2 is really wrong also... you need a meter to make ANY white accurate whether you change if the TV shows WTW or not. And if the TV doesn't show WTW you still won't have an accurate white without a meter and calibration software to adjust the TV to be accurate. TVs out of the box are NOT accurate (though some with THX modes might be fairly close).

#3 - isn't really wrong but it doesn't really capture the issue. The issue is... you use WTW when the display is capable of it because it does exist in some consumer video sources. And if the display doesn't do WTW, it's really not a huge deal - and by that I mean there are some displays that will NEVER show WTW no matter what you do to them adjustment-wise. Some people will not own a display like that because of the fear of losing information, but it's really not that big of a deal when it comes right down to it.

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post #21 of 23 Old 01-07-2012, 09:27 PM - Thread Starter
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This still indicates you don't understand the issue because none of those 3 "condensations" are right. If the TV shows WTW, the color is probably already screwed up because it hasn't been calibrated. So futzing with the controls that affect whether WTW is visible or not could make the color of white BETTER or WORSE... and you won't know which without a meter.

#2 is really wrong also... you need a meter to make ANY white accurate whether you change if the TV shows WTW or not. And if the TV doesn't show WTW you still won't have an accurate white without a meter and calibration software to adjust the TV to be accurate. TVs out of the box are NOT accurate (though some with THX modes might be fairly close).

#3 - isn't really wrong but it doesn't really capture the issue. The issue is... you use WTW when the display is capable of it because it does exist in some consumer video sources. And if the display doesn't do WTW, it's really not a huge deal - and by that I mean there are some displays that will NEVER show WTW no matter what you do to them adjustment-wise. Some people will not own a display like that because of the fear of losing information, but it's really not that big of a deal when it comes right down to it.

That is nothing but nit-picking & internal contradictions.
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post #22 of 23 Old 01-08-2012, 03:48 PM
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Whatever... you either have reading comprehension problems or can't parse your thinking into words that make sense. I couldn't tell which from your reply. All I'm trying to do is help you understand the issue/concept which your reply indicated was not true. If you want to take pot shots at someone trying to help you -- have at it.

If you don't understand the difference between what you wrote and the points I made in explaining each point, then I can't help you any further and won't try.

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post #23 of 23 Old 05-03-2013, 08:49 AM
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Originally Posted by snash22 View Post


That is nothing but nit-picking & internal contradictions.

Nit picking is preferred here actually. You'd be surprised how much some people obsess over squeezing that last %1 of performance out of what they own. :-)

But contradictions? Nah, they're pretty consistant....


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