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

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.

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


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.

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).


We don't agree about maintaining above white information, so the instructions are not expected to match.

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.

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.


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.

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.

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.

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.

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.