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For those struggling with brightness, contrast & backlight settings on LCD's

44857 Views 125 Replies 17 Participants Last post by MSL_DK, Apr 30, 2013

duke32

Discussion Starter · Aug 1, 2011

*This may be nothing new to a majority of the people here, but maybe it will help answer questions for some.*

Finally after piecemealing several threads together, I have come up with a method that works for me and maybe will help others newbies that are trying to figure out the relationship of brightness, contrast, and the back-light setting on LCD displays.

My equipment consisted of the AVS HD disc, an i1D2 and Chromapure.

Step 1: Brightness / black level

Use the black clipping pattern on the AVS HD disc. Crank your back-light up as high as it will go. It makes the flashing bars easier to see. Adjust the brightness until only 17 & up flash. Brightness is set for now.

Step 2: Contrast / White level

The 3 rules for setting contrast

1-No clipping

Use the white clipping pattern to see if your display clips at 235. Chances are it won't and you can 235 and above.

2-No discoloration

Here you need to use HCFR, ChromaPure, or CalMAN and your colorimeter. I am using ChromaPure and an i1D2.

Set your back-light to zero and put up either a 100% window or field. I checked both and had the same result. Set your contrast to about 75% and start raising it one step at a time. What you are looking for is when color is not being added anymore. You will most likely run out of red first. My red output peaked at a setting of 89/100. One step higher and red output dropped 3%. That is now the max your contrast can be without discoloration.

3-No eye fatigue

With my contrast now set and a back-light of zero, I was only outputting 17 ftL. I had to raise it to a setting of 3 to get 35 ftL. A setting of 4 gave me 43 ftL, and so on. In my normal viewing environment, either setting worked for me. I set mine at 3 for typical viewing. Make sure step 2 is still valid and your contrast and back-light are now set.

For a back-light check, go to the APL clipping pattern and make sure you can see 19-21 & up flash. If you can see below that, chances are your back-light may be too high.

This is the first time that I bothered checking all 3 rules on contrast and I have ended up with my best starting point heading to gray scale calibration. I didn't realize before how key step 2 is and the difference it makes.

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buzzard767

· #2 · Aug 1, 2011

...

Quote:
Originally Posted by duke32 /forum/post/20765766

Set your back-light to zero and put up either a 100% window or field. I checked both and had the same result. Set your contrast to about 75% and start raising it one step at a time. What you are looking for is when color is not being added anymore. You will most likely run out of red first. My red output peaked at a setting of 89/100. One step higher and red output dropped 3%. That is now the max your contrast can be without discoloration.

Out of curiosity, which ChromPure module were you using to measure color output?

For a back-light check, go to the APL clipping pattern and make sure you can see 19-21 & up flash. If you can see below that, chances are your back-light may be too high.

You're clipping 17 & 18. Black level is incorrect at this point.

duke32

Discussion Starter · #3 · Aug 1, 2011

I used the white balance module to measure color output. I guess you could use Raw, but I went with what was more visual.

How can Black level be incorrect? It was set and confirmed with the Black clipping pattern. If you're now going to raise the brightness based on the APL pattern, are you not going to start crushing Black? The method I used came from alluringreality's post here.
http://www.avsforum.com/avs-vb/showt...2#post20066562

Quote:
On the TVs I've looked at, a backlight or iris setting usually does not affect where a digital display clips. I use the first Black Clipping pattern to adjust the brightness control to the lowest setting where everything below 17 clips. In doing this it may be easier to spot the flashing in the pattern by setting the backlight high, and it may be more difficult to notice the flashing if the backlight is set low. Usually the backlight will not actually affect where the TV clips, so I consider it acceptable if you want to use a high backlight or walk up to the display to make the flashing easier to see.

Once you find the lowest brightness setting the TV is capable of using I would suggest moving on. Leave the TV at that brightness setting, go to the second APL Clipping pattern, set backlight to minimum, use typical room lighting, and view the TV from a location where you might usually watch. The white in the image and room lighting will probably make the flashing near black difficult to notice on most decent TVs. Start turning up the backlight control, and at some point you will likely be able to see 19 flash from your usual viewing location without touching the brightness control. Anyway, my point here is that clipping (brightness control) and light output (backlight control) usually are two different functions that don't necessarily interact. Room lighting can make near-black levels difficult to notice, and generally I would suggest turning up the backlight before increasing the brightness control.

buzzard767

· #4 · Aug 1, 2011

Quote:
Originally Posted by duke32 /forum/post/20765987

I used the white balance module to measure color output. I guess you could use Raw, but I went with what was more visual.

How can Black level be incorrect? It was set and confirmed with the Black clipping pattern. If you're now going to raise the brightness based on the APL pattern, are you not going to start crushing Black? The method I used came from alluringreality's post here.
http://www.avsforum.com/avs-vb/showt...2#post20066562

There is only one correct black level setting using that pattern - clip 16, see 17.

Jeroen1000

· #5 · Aug 1, 2011

While I own a plasma, a lot of things you said are valid here. Interesting read. I'm getting my meter soon and now the wait is getting worse haha.

PlasmaPZ80U

· #6 · Aug 1, 2011

Quote:
Originally Posted by buzzard767 /forum/post/20766521

There is only one correct black level setting using that pattern - clip 16, see 17.

I think the confusion here is about the clipping patterns. For the black clipping pattern (very low APL), you must see 17 and above. For the APL clipping pattern (medium/average APL), you must see at least 19 and above. The reason for this is that the white portions of the APL clipping pattern can make the black portions harder to see, making it harder to see 17-18 on some displays (but not all). These guidelines are from the pattern manual for the AVS disc.

buzzard767

· #7 · Aug 1, 2011

Quote:
Originally Posted by PlasmaPZ80U /forum/post/20766598

I think the confusion here is about the clipping patterns. For the black clipping pattern (very low APL), you must see 17 and above. For the APL clipping pattern (medium/average APL), you must see at least 19 and above. The reason for this is that the white portions of the APL clipping pattern can make the black portions harder to see, making it harder to see 17-18 on some displays (but not all). These guidelines are from the pattern manual for the AVS disc.

Agreed. However, once contrast is set a return trip to the black clipping pattern must be made to ensure nothing has changed. If it has, readjust.

Reactions: 1

PlasmaPZ80U

· #8 · Aug 1, 2011

Quote:
Originally Posted by buzzard767 /forum/post/20766657

Agreed. However, once contrast is set a return trip to the black clipping pattern must be made to ensure nothing has changed. If it has, readjust.

Yes, everything can affect everything.

redwolf4k

· #9 · Aug 1, 2011

Quote:
Originally Posted by duke32 /forum/post/20765766

Step 1: Brightness / black level

Use the black clipping pattern on the AVS HD disc. Crank your back-light up as high as it will go. It makes the flashing bars easier to see. Adjust the brightness until only 17 & up flash. Brightness is set for now.

Quote:
Originally Posted by buzzard767 /forum/post/20766521

There is only one correct black level setting using that pattern - clip 16, see 17.

Actually, the AVS disc is wrong. Every single blu-ray you own will display dithering(plasma) or elevated black level (LCD) if you set your brightness this way.

That test pattern is worthless, as well as the WoW test pattern. Those patterns only work when setting the black level for the black letterbox bars, or a tv that is displaying no signal.

In smooth gradations, like on all film, the settings resulting from those test patterns will results in elevated black levels.

Setting brightness how Joe Kane instructs, and using his smooth grayscale ramp test patterns with the video black indicators are the only way to set brightness correctly. This pattern will also show how the AVS and WoW patterns do not work, as the black level is elevated past the markers.

You lose no detail doing this. Those AVS/WOW patterns just display noise that should not be visible. You should barely be able to see a 11.5 IRE bar(4% above video black), with the traditional HD color bars provided by smpte. Somewhere along the line everyone started setting there brightness so 1% above video black was glowing. In reality you shouldn't see it at all.

Have any of you actually tested your blu-ray discs after you setup your brightness like this? Its a washed image with elevated black levels, always. Then the threads fill up with people saying the display looks washed out, and something is wrong. You want to set's black level as dark as it can be without losing actual detail, not as bright as it can be to ensure you may not be losing detail. You sacrifice color saturation, depth in the image, and contrast ratio just to display noise.

So now we have 3 opinions in the mix.

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Reactions: 1

ibre34

· #10 · Aug 1, 2011

WOW !

I am going to test this this evening and I am going to tell you my results tomorrow

What is the CORRECT plug for Contrast???? Because Joe Kanes' instruct are too subjetive.

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PlasmaPZ80U

· #11 · Aug 1, 2011

Quote:
Originally Posted by redwolf4k /forum/post/20766841

Actually, the AVS disc is wrong. Every single blu-ray you own will display dithering(plasma) or elevated black level (LCD) if you set your brightness this way.

That test pattern is worthless, as well as the WoW test pattern. Those patterns only work when setting the black level for the black letterbox bars, or a tv that is displaying no signal.

In smooth gradations, like on all film, the settings resulting from those test patterns will results in elevated black levels.

Setting brightness how Joe Kane instructs, and using his smooth grayscale ramp test patterns with the video black indicators are the only way to set brightness correctly. This pattern will also show how the AVS and WoW patterns do not work, as the black level is elevated past the markers.

You lose no detail doing this. Those AVS/WOW patterns just display noise that should not be visible. You should barely be able to see a 11.5 IRE bar(4% above video black), with the traditional HD color bars provided by smpte. Somewhere along the line everyone started setting there brightness so 1% above video black was glowing. In reality you shouldn't see it at all.

Have any of you actually tested your blu-ray discs after you setup your brightness like this? Its a washed image with elevated black levels, always. Then the threads fill up with people saying the display looks washed out, and something is wrong. You want to set's black level as dark as it can be without losing actual detail, not as bright as it can be to ensure you may not be losing detail. You sacrifice color saturation, depth in the image, and contrast ratio just to display noise.

So now we have 3 opinions in the mix.

I'm skeptical of your claims since it goes against all conventional wisdom. How many experts agree with this advice?

redwolf4k

· #12 · Aug 1, 2011

Quote:
Originally Posted by PlasmaPZ80U /forum/post/20767004

I'm skeptical of your claims since it goes against all conventional wisdom. How many experts agree with this advice?

I know...and thank you for not flaming.

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sotti

· #13 · Aug 1, 2011

We have a couple of issues

-Setting black level on displays that don't have a floating black level (LCDs).

-Setting black level on displays that do have a floating black level (Plasma).

-21 point or LUT based black level.

If the black level does not float, then code 0 and code 16 should produce the same luminance level.

If the black level does float then you should use a pattern that has a medium APL and set the brightness so code 0 and code 16 have the same luminance level.

Of course to do that accurately you need a meter that can read those very low light levels.

The overriding issue is that since we don't always have control over gamma, it's more important not to crush 4% than to have the ultimate black level. So if we have gamma control at 5%, then you can set it with a meter so that we have the correct luminance ramp up out of black. If we don't and we are crushing those first few steps, then you have to compromise.

As always the issue is how to compromise when displays don't work the way we'd want them to work in a perfect world.

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sotti

· #14 · Aug 1, 2011

A data point

code 17 at 2.2 gamma = 0.000709%

If you have 35fL at 100%, then 17 should be 0.000248fL.

Depending on a lot of conditions that may be below the threshold of perception. Granted we are typically talking about 1 or 2 clicks of brightness between where black disappears and when it actually is the same as 0.

serialmike

· #15 · Aug 2, 2011

Quote:
Originally Posted by PlasmaPZ80U /forum/post/20767004

I'm skeptical of your claims since it goes against all conventional wisdom. How many experts agree with this advice?

I completely agree with wolf. You use the DVE Grayscale ramps with the 2 dots at the end. You adjust brightness to the point where the dithering or stepping is at the 2 dots and your done.

The AVS disc with flashing is no good especially if you use the 17 number. The 19 sounds like that may be correct as per these new istructions I hadnt seen before.

Anyway I double checked wolfs method and he is correct spot on 100 percent true.

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alluringreality

· #16 · Aug 2, 2011

Quote:
Originally Posted by PlasmaPZ80U /forum/post/20767004

I'm skeptical of your claims since it goes against all conventional wisdom. How many experts agree with this advice?

Strictly-speaking the application portion fits with the instructions from Digital Video Essentials. The first level above black on their pluge is 2%, which I believe is luma 20. On some displays it is very easy to see the display's black and the darkest levels the display can create, especially close to the screen in an unlighted room. In certain conditions, it's possible to hard-clip everything below 2% gray and fit with their audio instructions. Like Sotti mentioned, there's not a lot of difference between video black and 2% in terms of display gamma math. I'm not convinced Digital Video Essentials necessarily intends to always cut off 17-19 gray luma, but their audio instructions support the position with some displays or viewing conditions.

My opinion is that black-level is a very simple control; it generally just changes where the display's black ends up in relation to video information. Generally any video information below the display's black is lost. Any information above the display's black will be reproduced according to the on-screen gamma produced by the display, and some displays may even have controls to affect on-screen gamma, or how the levels above the display's black are reproduced. Assuming you intend to watch the display from a certain distance, the only real variables are room lighting and other on-screen video levels. Generally more light in the room, or a brighter on-screen image, will tend to make near-black levels harder to discern. I'm not convinced that gray luma 17-19 is mere noise on the images I've looked at, so I tend to lean toward setting the display's black at video black (16 luma) and using room lighting to try to cover any display deficiencies. Some digital displays with poor black or near-black performance may have a better subjective appearance if you choose a compromise such as cutting off information above video black, like advocated by the Digital Video Essentials audio instructions.

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Razz1

· #17 · Aug 2, 2011

Quote:
Originally Posted by serialmike /forum/post/20767492

I completely agree with wolf. You use the DVE Grayscale ramps with the 2 dots at the end. You adjust brightness to the point where the dithering or stepping is at the 2 dots and your done.

The AVS disc with flashing is no good especially if you use the 17 number. The 19 sounds like that may be correct as per these new istructions I hadnt seen before.

I would appreciate it if someone could explain this method of adjusting brightness in some more detail. A simple step by step approach would be great. I don't understand what "dithering or stepping" is referring to. I think it would be interesting to see how this method compares to the other method that I have used which is AVSHD. Thanks.

duke32

Discussion Starter · #18 · Aug 2, 2011

Well, after all the discussion, I popped in the DVE grayscale ramp to compare with what I ended up with using AVS HD, and I could see no discernible difference between the two - YMMV.

alluringreality

· #19 · Aug 2, 2011

Quote:
Originally Posted by Razz1 /forum/post/20767853

I would appreciate it if someone could explain this method of adjusting brightness in some more detail.

It's from Digital Video Essentials, and the following fits with my memory:

Quote:
Originally Posted by redwolf4k /forum/post/20743365

make the 2% above video black bar disappear, and then increase brightness until it just appears. He then explains you should barely be able to see the 2% above video black bar, it should be "hard to see against the black background".

You can probably do the same thing with the APL Clipping pattern. Pause the disc to stop the flashing, so that you can see the vertical bars. Start by setting brightness much too low to get rid of most of the bars. Turn up brightness to the lowest setting where you can just barely see the bar marked 20.

Quote:
Originally Posted by duke32 /forum/post/20767912

Well, after all the discussion, I popped in the DVE grayscale ramp to compare with what I ended up with using AVS HD, and I could see no discernible difference between the two - YMMV.

Depending on room lighting, my display can result in a few clicks different brightness in going with the Digital Video Essentials instructions, but of course Avia doesn't exactly match Digital Video Essentials either. On my TV with proper room lighting, the difference in not clipping 17-19 is very subtle. Really it just depends how quickly the display comes out of black and room lighting.

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Razz1

· #20 · Aug 2, 2011

Quote:
Originally Posted by alluringreality /forum/post/20767965

You can probably do the same thing with the APL Clipping pattern. Pause the disc to stop the flashing, so that you can see the vertical bars. Start by setting brightness much too low to get rid of most of the bars. Turn up brightness to the lowest setting where you can just barely see the bar marked 20.

Is this APL pattern applicable to LCDs where all of the "extra and dynamic stuff" is turned off? I had thought that the APL side of things wouldn't be important for this type of display and these settings.

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