or Connect
AVS › AVS Forum › Display Devices › Display Calibration › AVS HD 709 - Blu-ray & MP4 Calibration
New Posts  All Forums:Forum Nav:

AVS HD 709 - Blu-ray & MP4 Calibration - Page 101

post #3001 of 3881
Quote:
Originally Posted by buzzard767 View Post

No, it does not. There is information above 234, Rec. 709 or not, so if your display handles it without clipping (it obviously isn't clipping), without color shifts, and without being so bright that it stresses your eyes and brain, so be it. It's head room - let it happen.

Read this.

There was an AVS thread I followed years ago where posters examined the issue of above 235 content.
One poster in the UK wrote a clever analysis program and examined a variety of sources for above 235 content. The consensus was that there is (sporadic) content but appeared to be due to encoder errors (aliasing) and in some cases improperly adjusted HD cameras used to record sports events.

Many LCD LED lit displays (mine included) can not be set to eliminate above 235. Because above 235 is minor, low level and sporadic it does no harm and has virtually no observable effect on PQ.

Your suggestions for setting contrast and additionally backlight for proper output, typically 15 - 35 fl depending on ambient illumination, are what all calibrators advise and is the method I have used for years.
post #3002 of 3881
Quote from THX:

"Where possible, we want to see the above white information (Above 235 to 255)"
post #3003 of 3881
Also, you don't have to "eyeball" individual color clipping at the top end of your contrast setting. There is a test pattern in the disc that lets you see when individual colors clip. Turn your contrast down until none clip. Red is often the problem.
post #3004 of 3881
Thread Starter 
Quote:
Originally Posted by Baswazz View Post

But then the contrast. by default as i mention above i see 230-253 flashing.
Regarding to the manual i have to change this, so i only see 230-234 flash.
But this i can't accomplish.

The intent of the portion you quoted is to say:
If your TV can clip below 235, don't clip below 235.

Your TV cannot clip in that range with user controls, so here is the relevant portion from the manual:
Some displays will show all the bars even on their highest setting. If your electronics still show all the bars at maximum, then clipping is good with the highest setting.

Like kjgarrison mentioned, you can look at Misc Pattern A4 to see if there's any color clipping. You'll probably find that your TV doesn't clip colors near 235 on the A4 pattern with the maximum contrast setting. That's totally fine. In fact my TV operates this way, and I consider it a good decision by the manufacturer. I say this because using the service menu I can use higher contrast settings, but any higher contrast just causes other problems on my TV.
post #3005 of 3881
Quote:
Originally Posted by alluringreality View Post

If the "power draw in both cases is identical" then I figure that something like a Kill-A-Watt meter would report similar numbers for a plasma TV when displaying either the white window or the 15% field from this project.

Great idea, I got out my clamp on current meter and made a couple of measuresments:

Power Peak RMS
100% white window 180W 156W
45% gray field 180W 125W

NOTE: 45% gray field produces a 16% APL on my display (gamma=2.28, .45^2.28=.16) I also measured the 45% window and full field to make sure they were 16% brightness compared to the 100% window. Meter precision is +/- 6W

So going by the peak power measurement I get what I expected but the rms is lower for the full field and I don't understand that. I don't know what the time constant for the rms circuit in the meter is so it's hard to know if the discrepancy is due to the meter or the display. If it is the display then alluringreality was correct in assuming it's harder for a plasma to generate a 15% average brightness using a window vs. a full field.
post #3006 of 3881
Hi. I have a question on the clipping pattern...I set my contrast so it shows all the bars (above reference white too 254), and then when I check the clipping pattern, it is still flashing all the way for RGB. So, I think I am OK.
Now, when I go to use S&M disc and the clipping pattern... it shows different result. In the S&M disc, I should be seeing concentric circle, but in the RED case, I cannot see the concentric circle unless I turn my contrast way down (from 50 to 32)...
So, is AVSHD clipping more "generous", or is S&M disc too stringent, or which one should I use to set my contrast to not have clipping?
post #3007 of 3881
Thread Starter 
Quote:
Originally Posted by fight4yu View Post

Hi. I have a question on the clipping pattern...I set my contrast so it shows all the bars (above reference white too 254), and then when I check the clipping pattern, it is still flashing all the way for RGB. So, I think I am OK.

I'll take it you're talking about A4.

Quote:


Now, when I go to use S&M disc and the clipping pattern... it shows different result. In the S&M disc, I should be seeing concentric circle, but in the RED case, I cannot see the concentric circle unless I turn my contrast way down (from 50 to 32)...
So, is AVSHD clipping more "generous", or is S&M disc too stringent, or which one should I use to set my contrast to not have clipping?

I don't see enough evidence to suggest that it's important for colors to extend beyond reference white, while Spears and Munsil appears to prefer to make sure to pass colors above reference white. I'm not aware of professional calibrators that do anything like measuring gamma on primary colors and extending beyond reference white (that's basically what the S&M pattern tests), so again I doubt that professionals necessarily concentrate on that aspect. In a perfect world sure it would make sense to calibrate all the way out with colors, but real-world my opinion is that it's a reasonable concession to simply calibrate for video between black and reference white. I suggest that you make sure the bright parts of A3 don't run out of light at the top-end (you should be able to see the steps near 235), so A4 will also flash above 235, and generally this is less strict than what I've read of the Spears and Musil suggestions.
post #3008 of 3881
Thanks! Yes, this is A4 I am talking about.
So, A4 is not the same as S&M Color Clipping, is that right? However, I thought A4 is used to track if RGB channel is clipping, so that does sound like what S&M is doing... However, S&M only have a few concentric circle, and maybe those are of a finer granularity and towards the top end?
I can't have contrast tune down that low, so I likely will make a compromise between color clipping and 13-14ftL setting that I want to target. However, I am just trying to understand why the difference results shown in A4 vs. S&M, because I thought they should both show RGB color channel clipping. It bugs me when one say I am OK and the other say I am way off
post #3009 of 3881
Thread Starter 
Quote:
Originally Posted by fight4yu View Post

I thought they should both show RGB color channel clipping.

Far as I know the Spears and Munsil pattern you are talking about just has some primary colors of various levels that abut each other. The A4 pattern has various levels next to the maximum level, and the bars flash to the maximum level. Basically their pattern compares various levels against each other, while A4 compares different levels against the maximum. I would tend to categorize their pattern as being more of a look at gamma (comparing different levels), while for A4 it's not possible to flash to a higher level if both levels are the same (higher level clipped). It sounds like your red probably shows little difference near where it runs out (clips), so in that case the S&M pattern might be hard to distinguish (little difference between levels) while A4 could still show flashing (higher levels not actually clipped off).

Quote:
It bugs me when one say I am OK and the other say I am way off

We don't agree about maintaining above white information, so the instructions are not expected to match.
post #3010 of 3881
If at the uppermost above white levels one color clips, then from that point on up it won't actually BE white will it?
post #3011 of 3881
Thread Starter 
Quote:
Originally Posted by kjgarrison View Post

If at the uppermost above white levels one color clips, then from that point on up it won't actually BE white will it?

If you're targeting a certain gray and your TV controls allow one color to run out in the grayscale, then yes you will not be able to make that gray any brighter than whatever you get where the color in the grayscale runs out. It's also possible that gamma might change for a color in the grayscale near where it runs out, which might also make it difficult to stay near a target gray above a certain point.
post #3012 of 3881
Quote:
Originally Posted by alluringreality View Post

If you're targeting a certain gray and your TV controls allow one color to run out in the grayscale, then yes you will not be able to make that gray any brighter than whatever you get where the color in the grayscale runs out. It's also possible that gamma might change for a color in the grayscale near where it runs out, which might also make it difficult to stay near a target gray above a certain point.

That "point" is where contrast should be set at or slightly below. I have used your disc in this way by setting my contrast at a point where the colors are all equally affected. This is always above 235.

I also have the S&M disc and use it in the same way, arriving at basically the same contrast setting. The flashing in your disc makes it easier to see.
post #3013 of 3881
I have a quick question about calibration. I have recently purchased a blue filter for calibrating my colors. Before, when calibrating using the AVSHD tool, I used to use the A3-Color Steps option (under Misc. Patterns) to adjust my colors. Since I now have a blue filter, I used it with the fourth option under 'Basic Settings' (Flashing Color Bars). With the flashing color bars my color settings for my TV are dramatically higher then when I only used the Color Steps (note, my contrast and brightness were nearly left unaffected by the color increase). However, the increase in color really messed up the 'Color Steps' pattern.

So, what I'm wondering is which pattern leads to more accurate colors? The TV looks good both ways with the blue filter calibration providing a more saturated picture and the color steps offering a desaturated picture but not devoid of color either. When others are calibrating their colors, which pattern do you use?

Note, if it is hard to understand the way I explained my situation let me know what didn't make sense and I'll try to elaborate.
post #3014 of 3881
Thread Starter 
Quote:
Originally Posted by JasonR66 View Post

Before, when calibrating using the AVSHD tool, I used to use the A3-Color Steps option (under Misc. Patterns) to adjust my colors.

I'm not sure what you mean here, unless one of the colors is running out and turning down color reduces the run-out. Turning down contrast may also reduce any run-out for the brighter portions on some TVs.

Quote:
Since I now have a blue filter, I used it with the fourth option under 'Basic Settings' (Flashing Color Bars). With the flashing color bars my color settings for my TV are dramatically higher then when I only used the Color Steps (note, my contrast and brightness were nearly left unaffected by the color increase). However, the increase in color really messed up the 'Color Steps' pattern.

Personally I'm not a fan of color filters on digital displays. I think they likely tend toward a too-high setting when compared to measurements. If you own one of the popular displays that has a thread in one of the other display forums I'd suggest to try to find out what sorts of color settings people get when they measure the displays. On some displays I think measurements are going to tend to be closer to the default setting than what a color filter suggests. Generally there's not much reason for manufacturers to set color too low by default, so if you're turning color much higher than the default setting I generally have to question the accuracy of the color filter.
post #3015 of 3881
@alluringreality

Thanks for your response. I used the color steps to adjust my color by trying to match the colored boxes to the white/gray boxes below them. My TV allows me to adjust Red, Green, and Blue color settings separately as well my TV's overall color setting. So, with the color steps, I could really fine tune my color settings by my eye.

With the blue filter, the color steps clip at the top three higher (and lighter) boxes. This leads to a more saturated picture but one that I'm not sure is accurate. It does look really good though so I'm not sure what I think yet. I've kept both calibrations so I guess I could test this new calibration for a while and see what I think and switch back if I feel it is necessary.

By the way, I have a Vizio VL370M and the thread associated with that TV has a lot of calibration. Mostly from me though.

Thanks for your help.


EDIT:

Just a quick update. I decided to calibrate my TV around the blue filter and the color steps pattern and put each calibration's settings in to two separate video presets on my TV. Then, I compared the two switching back and forth between the calibrations. The blue filter, to my eyes, lead to more vivid, realistic colors. The skin tones, using the color steps, looked a little pale whereas, with the blue filter, the tones look accurate. But, the change wasn't huge (though the numbers would have you believe differently).
post #3016 of 3881
Thread Starter 
Quote:
Originally Posted by JasonR66 View Post

I used the color steps to adjust my color by trying to match the colored boxes to the white/gray boxes below them. My TV allows me to adjust Red, Green, and Blue color settings separately as well my TV's overall color setting. So, with the color steps, I could really fine tune my color settings by my eye.

I still don't know what you're talking about, so I think it's possible you're trying to use the controls in some other way than how they're intended. Sure some TVs do have further grayscale and color controls beyond just color and tint, but they're usually set from measurements, and I'm still not sure how that pattern would apply. The main reason for the pattern is just to check if the colors are running together in the brighter portions. On some displays the brightest color and the bar below it might be about the same brightness, so you can't really distinguish the two bars, and reducing contrast might make it so you can see the two brightest bars.
post #3017 of 3881
@alluringreality

...oh. Heh, yeah. I just realized what I've been doing wrong.

Thanks.
post #3018 of 3881
Quote:
Originally Posted by alluringreality View Post

It depends how you want to try to make an approximation. Just averaging the video levels doesn't make sense, because a white window clearly puts a lot more strain on plasma or CRT than a field of the same average. What I mean is that a 100% gray (reference white) window at 15% area would average to 15% gray, and I don't think many would argue that a white window is more difficult for plasma or CRT to produce than a 15% gray field. Probably a more reasonable thing to do is to gamma-adjust video levels before averaging, since in effect that's what the TV has to do with the light output. The 15% area white window would still have a gamma-adjusted average of 15%, but the matching field after a 2.2 gamma adjustment would be around a 42% gray field (.42^2.2~15%).

If I put a single-point curve adjustment on the image to approximate 2.2 gamma, here are the results:

Small APL -> gamma-adjusted average around 4.7%, which would be similar to a 25% gray field (.25^2.2~4.7%)

Large APL -> gamma-adjusted average around 24.7%, which would be similar to a 53% gray field (.53^2.2~24.7%)


As examples of random somewhat bright images (white in uniforms), here was the current headline from NFL.com http://www.nfl.com/news/story/09000d...P11_cp#photo=1

If I convert the images to black and white and then follow the same procedure, here are the results:

Image 1 -> gamma-adjusted average around 17.6%
Image 2 -> gamma-adjusted average around 23.5%
Image 3 -> gamma-adjusted average around 21.6%
Image 4 -> gamma-adjusted average around 12.9%

For examples of random movie images, the Blu-ray posts from the Star Wars http://www.avsforum.com/avs-vb/showt...6#post20965206

Post #3 -> gamma-adjusted average around 15.7%
Post #4 -> gamma-adjusted average around 21.6%
Posts #5 & #6 -> gamma-adjusted average around 2.4%

So calibrating using the Windows vs APL Small vs APL Large should not make a difference with LCD or LED TVs?

How about a SXRD RP with all the Iris, Contrast Enh, Black Level Corrector, etc. turned OFF?
post #3019 of 3881
Hey guys, since the 709 window patterns are large compared to what signal generators have as well as manufacturers in house (under 10% for plasma) ,why do we simply not add some smaller windows to the disc?
post #3020 of 3881
I would be in favor of a set of small windows if they were displayed over everyday images for us folks with "dynamic" displays. I don't think this would be too difficult, one could analyze a type of movie (dark, normal, animated, etc.) or news/sports content, and find a mean and standard deviation video level and then pull a frame that was representative of that mean/sd for a background.
post #3021 of 3881
I think it would be a good idea also. The reality is that these sets can be made to measure "Great" or "lousy" with the same settings, meter and calibration software based solely on the kind of source pattern used. This means to me, that until a source pattern type is agreed on, and related in some way to real content, that calibrating these 'dynamic'' sets is a bit of a pointless activity.

In trying to come to grips with this issue on a GT30, I used the approach that the THX folks must know what they are doing. Of all the source patterns on the AVSHD 709 disk I tried, Small APL Windows gave the best Gamma curve for the THX defalut settings. So, when I did my own work, I used those patterns.
post #3022 of 3881
Yepp, the pros are using such smaller patterns and many of us cannot afford $1k to $5k on a generator.
post #3023 of 3881
Quote:
Originally Posted by Dave_O View Post

This means to me, that until a source pattern type is agreed on, and related in some way to real content, that calibrating these 'dynamic'' sets is a bit of a pointless activity.

Not quite pointless, results even when you don't pay attention to the limitations of display/pattern are significant improvements over factory settings. At least this is the case for Samsungs, I know the GT30 has a more limited calibration control space.
post #3024 of 3881
Quote:
Originally Posted by zoyd View Post

Not quite pointless, results even when you don't pay attention to the limitations of display/pattern are significant improvements over factory settings. At least this is the case for Samsungs, I know the GT30 has a more limited calibration control space.

More of a theoretical comment. Calibration consists of feeding the TV a defined set of inputs, adjusting the TV to produce a defined set of output measurements, 65K, 2.2 Gamma, etc. Without an agreed upon standard source, one will end up with many different settings producing the desired output.

This does not seem to be the case with an LCD set, at least those without any 'local dimming'.
post #3025 of 3881
Let me ask this, if you really wanted to use the 15% windows on avs for grayscale, would that not be fine. You just need to use apl large for gamma?
post #3026 of 3881
Thread Starter 
Quote:
Originally Posted by N3W813 View Post

So calibrating using the Windows vs APL Small vs APL Large should not make a difference with LCD or LED TVs?

How about a SXRD RP with all the Iris, Contrast Enh, Black Level Corrector, etc. turned OFF?

SXRD with the dynamic settings off generally performs similarly to LCD with fixed backlighting. With these sorts of displays light output is often tied closely with the video level, so there will likely be little variation regardless of average picture level. Odds are that measuring any of the 4 pattern types on the disc would result in similar measurements, but you can always test an individual display to see how it performs.
post #3027 of 3881
Thread Starter 
Quote:
Originally Posted by AtDaBeach View Post

Let me ask this, if you really wanted to use the 15% windows on avs for grayscale, would that not be fine. You just need to use apl large for gamma?

All of the patterns use identical center video levels. The only difference between the patterns will be the average brightness of the on-screen image. I cannot say if, or how much, grayscale might vary on an individual display depending on the average brightness of the on-screen image. Usually there isn't expected to be much grayscale variation depending on average brightness, but how well that applies to particular models I cannot say. Of course this is something you can test simply by comparing how much xy measures vary between different patterns.
post #3028 of 3881
Quote:
Originally Posted by alluringreality View Post

All of the patterns use identical center video levels. The only difference between the patterns will be the average brightness of the on-screen image. I cannot say if, or how much, grayscale might vary on an individual display depending on the average brightness of the on-screen image. Usually there isn't expected to be much grayscale variation depending on average brightness, but how well that applies to particular models I cannot say. Of course this is something you can test simply by comparing how much xy measures vary between different patterns.

On our Samsung plasmas with Dynamic Contrast OFF, at least the D8000 series in my case, your Misc A5 pattern, called "Fluctuating Brightness" I believe, shows fluctuations in the brightness of the grey scale in the lower right as the pattern goes through the steps. It is not the same as the step-by-step change in brightness that Dynamic Contrast produces, and the fluctuation does not occur at every different level of grey. This is not the case in my Samsung LCD, where the grey scale does not change.

I presume this is what this pattern is there for, and I wonder if this is a problem that's been around for awhile, else why would this test be included.
post #3029 of 3881
Thread Starter 
Quote:
Originally Posted by kjgarrison View Post

I presume this is what this pattern is there for, and I wonder if this is a problem that's been around for awhile, else why would this test be included.

In the portion you quoted I was just saying that xy values from measurements on the CIE diagram are generally not expected to vary much, regardless of the pattern chosen. The pattern 'A5 - Dynamic Brightness' has more to do with gamma, Y measurements, or light output (rather than xy measurements). One of the reasons for including the Dynamic Brightness pattern was simply to look at how some display controls function, and it can also be used to observe that various displays react differently to changes in average brightness.

The "Black Level Bars + Steps + Varying Gray" pattern on the Avia II DVD is a similar idea. That pattern also has some constant video level bars on the screen and average brightness increases as the video plays. Either the Dynamic Brightness pattern or the Avia video hint at the issue of measuring typical windows while trying to "calibrate" gamma. As these patterns indicate, various displays simply do not perform similarly regarding light output as average brightness changes. When someone measures Y with typical windows they are measuring a changing average brightness, along with measuring different video levels. With the APL measurement patterns they are only measuring different video levels, while average brightness remains constant for the series. Measuring gamma with windows is sort of similar to trying to measure the bars from one of the patterns mentioned as the video plays (See Example). Measuring the APL series is similar to pausing one of the patterns mentioned (so average brightness remains constant) and looking at the bars.

Example: Typically on consumer plasma the light output (Y measure) of the bars will change as average brightness adjusts, and usually with fixed backlight LCD the light output (Y measure) for individual video levels remains constant as average brightness changes - which is basically what you stated.
post #3030 of 3881
Just got this back from Spears and Munsil, with an inquiry about smaller windows.

Quote:


Thank you for the feedback. We will have windows and fields on the next disc, which we hope to get out in March or April. There have been many hold-ups, mostly around tools for 3D encoding.

Our standard window size will be 10%. We will have a constant APL type pattern where the window is 6 or 7% in size. The constant pattern will cover 0, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, and 100% APL. For regular windows, we will go from 0% to 108% in 5% steps. Maybe 2.5% steps from 0 to 20 since that is where gamma changes the most.

Best,

Stacey
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Display Calibration
AVS › AVS Forum › Display Devices › Display Calibration › AVS HD 709 - Blu-ray & MP4 Calibration