LG Black Level settings

[Remicade]

My TV have 2 options for Black Level: Low (image is darker) and High (image is brighter). Question is: Low is Video Level and High is PC level ? My ATI 4670 what level output ? How can I know ? What value use for Backlight settings ?

[QBhd]

Black Level High on TV and RGB Full on the video card

QB

[hello_hello]

Mine has the same options, only they're called "lower" (image is darker) and "normal". Lower is actually the PC levels setting, while normal is TV levels. It's not actually to do with the backlight as such, it's to do with the range of levels. Somewhere in the chain a PC should expand the TV levels (16-235) to PC levels (0-255) for displaying on it's own monitor, but they're not always set up correctly.

There should be options in your video card's control panel for changing levels so you'd have to look in there to see if it's currently changing them. I've got an Nvidia card and it's got three options.... use the player settings, TV, or PC levels. So then you need to work out which levels your player is using. As far as I know the old Windows renderers (WMR9 etc) don't change the levels. I think the EVR renderer and Haali automatically convert from TV to PC levels.

[QBhd]

Mine has the same options, only they're called "lower" (image is darker) and "normal". Lower is actually the PC levels setting, while normal is TV levels.

I am willing to bet that you are misunderstanding those settings on you TV. I too used to think the "darker" setting was PC Levels (FUll RGB), but as it turns out, that is not the case. A simple still image test pattern proves that, since it will bypass all player settings and filter settings that can mess with black levels of calibration files.

This is a good image:

Levels.bmp (http://www.ian-kennedy.com/Video/Levels.bmp)

QB

[Ghitulescu]

I am willing to bet that you are misunderstanding those settings on you TV. I too used to think the "darker" setting was PC Levels (FUll RGB), but as it turns out, that is not the case.

Indeed :)

Darker means that the TV expands the PC levels it receives to fill in the whole dynamic range thinking they are TV levels. Leaving this setting to Normal, the TV will scale it 1:1 and it will most probably clip it below and above.

[iSeries]

I own three LG TVs, a 37" LCD bought 3 years ago, a 47" LCD bought 2 years ago, and a 60" plasma bought 3 months ago.

On all three, 'High' black level = PC levels. But remember to set your video card to RGB Full 0-255 as well, as QBhd says.

[hello_hello]

Darker means that the TV expands the PC levels it receives to fill in the whole dynamic range thinking they are TV levels. Leaving this setting to Normal, the TV will scale it 1:1 and it will most probably clip it below and above.

I'm fairly sure the PC is outputting TV levels.

[Remicade]

I made a comparison between low and high, before every screenshot I calibrate the TV with AVS HD 709:
Image comparison (http://screenshotcomparison.com/comparison/105851) the image is taken with print screen I notice sharpness is different :(
When I calibrate: - with low black level I can see all the flashing bar in 1-Black Clipping.mp4 and 3-White Clipping.mp4
- with high black level I can see only 17-25 flasing bar in 1-Black Clipping.mp4 and only 230-233 flashing bar in 3-White Clipping.mp4 whatever value I choose for brightness and contrast

[hello_hello]

I am willing to bet that you are misunderstanding those settings on you TV. I too used to think the "darker" setting was PC Levels (FUll RGB), but as it turns out, that is not the case. A simple still image test pattern proves that, since it will bypass all player settings and filter settings that can mess with black levels of calibration files.

This is a good image:

Levels.bmp (http://www.ian-kennedy.com/Video/Levels.bmp)

I very well could be misunderstanding this HDMI black levels thing, and I'll have to play around a little more to try to get my head around it and I've found some reading on the subject, but for the moment.....

It seems from the bit of reading I just did the different HDMI black level settings don't equate to PC or TV levels as such, as they only effect black, not whites.

When the PC is connected via VGA and it's outputting TV levels I'm fairly sure the picture is correct. At least I hope it is. It looks right to me.
When I then connect it via PC/HDMI input, which is the only one where the TV lets me change the black level thingy, it looks exactly the same as the VGA input when it's set to "normal" (PC still outputting TV levels).

I'd actually boosted the gamma a bit for the Bluray player's input to get it to match the PC's picture, but now I think it's probably something to do with this HDMI black level, but when I disabled HDMI deep color (or whatever it's called) in the Bluray player nothing changed, it still looks a little too dark to me. However I only tested it playing an AVI via USB. Chances are the Bluray player is too dumb to change black levels if you're not using a disc. It won't change refresh rates when playing video via USB.

Also, if I change the TV from "normal" to "lower", it does seem to mess with the colors Windows produces a little (Windows itself, not just the video) so I stayed with using "normal".

Anyway, I just tried your test image. Either with the PC connected via VGA or HDMI (input set to "normal") I can see the difference between black levels of 0 and 16 (which I thought was correct). When changing the setting to "lower", 0 and 16 black levels are the same black. White levels are unaffected. So to me the black level setting is just to make blacks blacker but I'm not sure if I like it. On my Plasma at least it seems to make the picture too dark, like there's too much contrast.

Maybe from all the above you can help me understand what the HDMI black levels is supposed to achieve, but for the moment I still think the picture looks "correct" without it. I'll do some more reading and experimenting later today when I have some more time.

PS. I've got all the TV's enhancements disabled. Dynamic contrast, that sort of thing. Do any of them interact with the HDMI black levels setting directly? ie would dynamic contrast work differently if I set the HDMI black level to "lower" or would it just suck regardless?

[QBhd]

@ hello_hello:

A PC conected via VGA is only outputting PC Levels (AFAIK), and if you see the difference of 0 and 16 then your TV is on PC Levels with the "Normal" setting. I disable all post processing on my TV as well (dynamic contrast, colors and any such thing) Are you using madVR as a render for PC playback? Understanding your levels is definately a worthwhile venture since you can then know what to change and where to change it in your playback chain.

For me, I disable all postprocessing in PotPlayer so it does not molest the levels, I leave LAV Video as "levels untouched" (almost all video will be TV Levels), FFDShow RAW Video filter is set to TV levels, madVR is set to PC Levels and the video card is then set to PC levels and finally the TV is set to PC levels ("Black Level"=High for my LG). In this chain, only madVR touches the levels and it does this in the best possible way. From what I have read, the video cards do not do a good job at level conversion and thus it is best to leave then as they are are PC levels, plus if you want to play a game through the PC or look at pictures, they will not look right if the video card is attempting to output at TV levels.

QB

[QBhd]

I made a comparison between low and high, before every screenshot I calibrate the TV with AVS HD 709:
Image comparison (http://screenshotcomparison.com/comparison/105851) the image is taken with print screen I notice sharpness is different :(
When I calibrate: - with low black level I can see all the flashing bar in 1-Black Clipping.mp4 and 3-White Clipping.mp4
- with high black level I can see only 17-25 flasing bar in 1-Black Clipping.mp4 and only 230-233 flashing bar in 3-White Clipping.mp4 whatever value I choose for brightness and contrast

Unfortunately, that screenshot comparison is not quite good enough since it is not the exact same frame. For video playback, you do NOT want to see flashing bars from 0-16 and seeing up to 233 is also acceptable

QB

[hello_hello]

A PC conected via VGA is only outputting PC Levels (AFAIK), and if you see the difference of 0 and 16 then your TV is on PC Levels with the "Normal" setting.

I almost finished writing a lengthy reply but then thought to try something, and yes it appears I may be using the wrong levels on the TV, which is monumentally disappointing given I really like the picture. I guess I'll have to start over with the TV calibration.

Anyway it occurred to me that I first realized the video levels using the PC monitor were incorrect because on the odd occasion I played video where the black bars hadn't been cropped it was obvious they were dark grey compared to the black of the "unused" screen area. So I found a 4:3 widescreen DVD and tried it on the TV and sure enough, the black bars top and bottom are dark grey compared to the black down each side. Are typing lots of expletives frowned upon in this forum? I feel a need....

I don't want to use the "low" setting on the TV because it does seem to mess with Windows colors as well as the video, and I actually don't want it too much darker than it is at the moment anyway.... but later on when I've got a bit of spare time I guess I'll change the graphic card's setting to PC levels for video and have a re-think re the TV calibration. Bummer....

[Asmodian]

Using my LG plasma TV I found that I could make basically the same picture by setting black to low and raising the brightness or setting it to high and lowering the brightness.

There is no difference even displaying blacker than black because if you expand TV to full range and set 0 = TV full black (black level = High) or leave it in TV range and set 16 = TV full black (black level = Low) it looks the same after calibration. Because Windows uses full range I decided it was best to leave the TV on full range (high black level) and have MadVR expand TV range video to full range.

If connected to a computer I suggest keeping the video card set to full range and the TV's black level set to high. Make sure MadVR is outputting full range and calibrate the black level (and the white level if you can but the black level is easier imo). You do not want to see blacker than black or whiter than white.

I also think that people are used to TVs and monitors that have their brightness set a bit too high. Manufactures set bightness higher because it looks better to people in the store but it makes artifacts more obvious and gives a slightly "washed out" look to the picture. After calibrating my TVs and monitors I thought I had something set wrong because it was harder to see details in the shadows but if I stopped looking at just the shadows everything else looked "better". Maybe my TV just has bad resolution in shadows, given that it is a plasma I suspect this is it.

[hello_hello]

Using my LG plasma TV I found that I could make basically the same picture by setting black to low and raising the brightness or setting it to high and lowering the brightness.

Fortunately, to get back to where I was that's pretty much all I had to do too. I changed the PC's video output to PC levels and just turned up the brightness a little while leaving the TV's level on normal (probably the same as your "high" setting).

I don't think it's exactly the same as it was though. There's definitely more contrast than before but sometimes I like it, while sometimes I don't. It depends on the video. I did take me all of about 30 seconds to get used to it though so I guess it can't be bad. At one stage I switched back to the old settings and for 30 seconds that looked wrong too.

It also seems I was wrong in an earlier post when I said it only seems to effect blacks and not whites, although I can't see a huge change at the white end. I read a little about it on Samsung's website and I'm pretty sure they referred to it as 0-255 vs 16-235 at one point.

[Remicade]

I changed my DVI-HDMI cable with another HDMI-HDMI and I have option Pixel format RGB 4:4:4 Pixel Format Studio and Pixel Format PC Standard (with DVI-HDMI i don't have this). With DVI connection my ATI 4670 output PC Level 0-255 because he expects a PC monitor at the end of the cable ?

[Ghitulescu]

Not all TVs support 4:4.4, but the situation might improve in the future. All commercial sources do not exceed 8b, so why bother? :)

[Remicade]

Well in my ATI CC (4670) i have only 2 option with 4:4:4, I don't have something with YCbCr.

[Asmodian]

With DVI connection my ATI 4670 output PC Level 0-255 because he expects a PC monitor at the end of the cable ?

Yes. This can happen on the other side too; some TVs will assume PC levels if the refresh rate is 60Hz.

Not all TVs support 4:4.4, but the situation might improve in the future. All commercial sources do not exceed 8b, so why bother? :)

I belive Remicade is talking about RGB, are there really some TVs that do not support RGB input? That would be terrible, how do they decide if it is rec.601 or rec.709? :(

[hello_hello]

My video card gives me two output options when connected via DVI to HDMI, RGB or YCbCr444.
Best as I can tell the latter automatically outputs to PC levels as if I also set the video card to expand the levels to "PC" the picture is obviously way too dark.

That aside, there seems to be a minor difference between the two. RGB seems to be more likely to show any blocking a little more in darker areas, although I can't tell if that's simply because there's a difference in contrast between the two as it takes too long to switch between them, but I can see RGB definitely reveals any blocking a little more.
Edit: I also just tried a video with some "banding", and while there's not a huge difference, the banding is less obvious with the video card set to YCbCr444.

Theoretically though, should there be any advantage to using one over the other?

[hello_hello]

I belive Remicade is talking about RGB, are there really some TVs that do not support RGB input? That would be terrible, how do they decide if it is rec.601 or rec.709? :(

Does the TV actually decide colorimetry? Given a PC would connect to the TV at full resolution would the TV even be aware of the video's original resolution?

With my video card set to output YCbCr444 the colorimetry is still changing according to the resolution (I tested it by running a video full screen and changing it's resolution with ffdshow). I don't quite understand where the colorimetry decision is being made as I thought colorimetry was only decided when converting to RGB.

[Asmodian]

I suspect there is a conversion to RGB (MadVR?) and the video card is converting back to YCbCr to send it to the TV.

[Remicade]

Nothing happens on the screen if I switch between RGB 4:4:4 Limited RGB and Full RGB the hole thing of this Black Level are a mystery for me, I think I calibrate the picture with my eyes and when I find a settings will use. I give up :D.
Whatever I choose if I calibrate the TV the results are ~ the same.

[Ghitulescu]

Define calibrate :)

[hello_hello]

Remicade,
It may depend on whether the levels are being changed by your renderer or video player.
For instance (well this is how it works using my Nvidia card anyway) if I use a renderer such as Haali which automatically expands TV levels to PC levels, then changing the levels in my video card's control panel has absolutely no effect. I don't understand how it works, but the video card seems clever enough not to try to expand the levels a second time or convert it back to TV levels. If I use the WMR9 renderer (which doesn't change the levels) then I can elect to expand them using my video card.

What player/renderer are you using? It may be the reason you're not seeing any difference when switching between limited RGB and full RGB. If the renderer is already expanding the levels and that's why changing the setting on your video card has no effect, then in theory you'd probably want to go with the high black level on your TV. The way I understand it now the high level is for when your PC is already outputting full RGB and the low level is for when the PC is outputting TV levels (or limited RGB), in which case the levels are expanded by the TV.

I'd assume using the default TV settings for brightness and contrast etc, if your PC is already outputting expanded levels then choosing the low black level on the TV would make the picture look way too dark.

You could also try testing it using the method I mentioned earlier. If you play a video on the PC which contains black bars and compared to an actual black screen they look dark grey, then you should at least know know the levels aren't being expanded by the PC, and choosing the low black setting on the TV should make the black bars black.

[Remicade]

I calibrate with AVS HD 709. I'm using MPC HC with LAV and madVR. Well my setup right now is RGB Full on ATI CC, Video Levels on madVR , LG on Low.

[QBhd]

I calibrate with AVS HD 709. I'm using MPC HC with LAV and madVR. Well my setup right now is RGB Full on ATI CC, Video Levels on madVR , LG on Low.

If you don't use the LG for anything other than video, that is okay... but it is best to have madVR at PC Levels and the LG on High since you never know when you will want to play a game or view pictures on the big screen, and they will not be at the correct color levels... You never want your TV to clip the color space that the PC is outputting

QB

[Remicade]

Thanks for the advice, right now I'm using for movies.

[Remicade]

You was right LG on HIGH 0-255 is the correct setting and madVR PC levels. I'm convinced myself. Thank all guys I resolved Black level issue and judder problem (http://forum.doom9.org/showthread.php?p=1547790#post1547790).