Need advice on preventing red clipping on Samsung D6000 - AVS Forum
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post #1 of 9 Old 08-08-2012, 08:55 AM - Thread Starter
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I am trying to dial in the "Standard" mode on a UN55D6000 Samsung LED driven LCD set.

I have ensured that Dynamic contrast is OFF, and balanced the color control via the blue mode on the tv. The result was "48".

When looking at the AVS HD 709 calibration disc's grayscale section, cycling to the primary color upper end section (the one just before the grayscale uniformity cycling pattern) I run into the problem of red clipping before it reaches 234.

With color balanced, I must dial the set all the way back to a contrast setting of 80. This is using the "Native" color space. In "Auto" I can squeeze a bit more contrast, maybe to 82 out of it (I am aware auto is the closest to Rec 709).

If I under saturate the colors, say dialing back the color control to 45, I can get more contrast out of the set, say up to 85.


How should I approach this? White contrast test patterns give good colorless results up until the 95 range, almost maxed, and the other primaries: blue and green can also survive a high contrast setting and a balanced color control. Red is the only one that falls short.


I think undersaturated colors and a rather low contrast setting in order to see full red detail is a bit upsetting.


Is there anything else I need to adjust to fix red from clipping?
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post #2 of 9 Old 08-08-2012, 09:00 AM
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Quote:
Originally Posted by redwolf4k View Post

I am trying to dial in the "Standard" mode on a UN55D6000 Samsung LED driven LCD set.
I have ensured that Dynamic contrast is OFF, and balanced the color control via the blue mode on the tv. The result was "48".
When looking at the AVS HD 709 calibration disc's grayscale section, cycling to the primary color upper end section (the one just before the grayscale uniformity cycling pattern) I run into the problem of red clipping before it reaches 234.
With color balanced, I must dial the set all the way back to a contrast setting of 80. This is using the "Native" color space. In "Auto" I can squeeze a bit more contrast, maybe to 82 out of it (I am aware auto is the closest to Rec 709).
If I under saturate the colors, say dialing back the color control to 45, I can get more contrast out of the set, say up to 85.
How should I approach this? White contrast test patterns give good colorless results up until the 95 range, almost maxed, and the other primaries: blue and green can also survive a high contrast setting and a balanced color control. Red is the only one that falls short.
I think undersaturated colors and a rather low contrast setting in order to see full red detail is a bit upsetting.
Is there anything else I need to adjust to fix red from clipping?

the correct mode to calibrate on the Samsungs is movie mode


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post #3 of 9 Old 08-08-2012, 10:10 AM
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Native mode is NOT the mode you should be using either. You should be using Rec709 or BT709 or HDTV.

There's nothing inherently bad in turning Contrast down to 80 to avoid clipping any color (or white). And depending on the Backlight setting you are using, 80 could be too high. In general, Backlight should be in the middle or below the middle of the setting range to keep blacks from going gray-ish. The lowest Backlight setting will produce the darkest blacks but may not make white bright enough... depends on brand and model.

You want Movie mode and you want HDTV color space (which may be called Rec709 or BT709). "Native" mode means you get the full-spectrum range of the LEDs with zero correction. That means every color will be inaccurate all the time. There is no good reason to ever use Native mode -- it may as well be labeled "The most inaccurate mode this TV has available".

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post #4 of 9 Old 08-08-2012, 10:20 AM
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Originally Posted by Doug Blackburn View Post

Native mode is NOT the mode you should be using either. You should be using Rec709 or BT709 or HDTV.
There's nothing inherently bad in turning Contrast down to 80 to avoid clipping any color (or white). And depending on the Backlight setting you are using, 80 could be too high. In general, Backlight should be in the middle or below the middle of the setting range to keep blacks from going gray-ish. The lowest Backlight setting will produce the darkest blacks but may not make white bright enough... depends on brand and model.
You want Movie mode and you want HDTV color space (which may be called Rec709 or BT709). "Native" mode means you get the full-spectrum range of the LEDs with zero correction. That means every color will be inaccurate all the time. There is no good reason to ever use Native mode -- it may as well be labeled "The most inaccurate mode this TV has available".

On the Samsungs, the available modes are Auto, Native, and Custom (Full 3D CMS in this last mode, which is only on higher end models). Native is wrong 99% of the time (unless you measure it to be more accurate than Auto, which is highly unlikely but not impossible) and Auto is best if you have no CMS and Custom is best if you do have CMS.


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post #5 of 9 Old 08-08-2012, 10:26 AM
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Quote:
Originally Posted by redwolf4k View Post

I am trying to dial in the "Standard" mode on a UN55D6000 Samsung LED driven LCD set.
I have ensured that Dynamic contrast is OFF, and balanced the color control via the blue mode on the tv. The result was "48".
When looking at the AVS HD 709 calibration disc's grayscale section, cycling to the primary color upper end section (the one just before the grayscale uniformity cycling pattern) I run into the problem of red clipping before it reaches 234.
With color balanced, I must dial the set all the way back to a contrast setting of 80. This is using the "Native" color space. In "Auto" I can squeeze a bit more contrast, maybe to 82 out of it (I am aware auto is the closest to Rec 709).
If I under saturate the colors, say dialing back the color control to 45, I can get more contrast out of the set, say up to 85.
How should I approach this? White contrast test patterns give good colorless results up until the 95 range, almost maxed, and the other primaries: blue and green can also survive a high contrast setting and a balanced color control. Red is the only one that falls short.
I think undersaturated colors and a rather low contrast setting in order to see full red detail is a bit upsetting.
Is there anything else I need to adjust to fix red from clipping?

To summarize what you should do in order:

1) Select Movie pic mode

2) Select Auto color space (since you can't use the CMS without an accurate meter)

3) Set contrast to avoid white clipping below 235 and also R,G,B clipping below 235

4) Set color via blue only mode (though be prepared to tweak it with reference material afterwards)


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post #6 of 9 Old 08-08-2012, 10:40 AM - Thread Starter
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Thanks.

I will do this.

Luckily the set is pretty accurate out of the box in the movie mode. So good in fact I didn't have to use the 10pt. grayscale controls, only the 2 pt, and there is no visual difference.

The "Auto" color space is practically dead on with the primaries as well, the secondaries are SLIGHTLY off but not noticeable.

The white point is near perfect as well, very happy.



I have no problem preventing color detail clipping in "Movie" mode, even at high contrast settings. I found the set works best at around half back light, 10/20. Its around 35ftl and doesn't start to bleed through the blacks much at all. I would guess the contrast ratio is ideal at this spot like you said (Doug).


There is not to much to tweak luckily. The D series from last year seem to be great in color and grayscale department out of the box.


I still wish I could figure out why the Standard mode, (When matching all settings to Movie mode) still clips red unless contrast is set way down. It must be some sort of internal processing I cannot control.


Thanks Everyone!
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post #7 of 9 Old 08-08-2012, 10:44 AM
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Quote:
Originally Posted by redwolf4k View Post

Thanks.
I will do this.
Luckily the set is pretty accurate out of the box in the movie mode. So good in fact I didn't have to use the 10pt. grayscale controls, only the 2 pt, and there is no visual difference.
The "Auto" color space is practically dead on with the primaries as well, the secondaries are SLIGHTLY off but not noticeable.
The white point is near perfect as well, very happy.
I have no problem preventing color detail clipping in "Movie" mode, even at high contrast settings. I found the set works best at around half back light, 10/20. Its around 35ftl and doesn't start to bleed through the blacks much at all. I would guess the contrast ratio is ideal at this spot like you said (Doug).
There is not to much to tweak luckily. The D series from last year seem to be great in color and grayscale department out of the box.
I still wish I could figure out why the Standard mode, (When matching all settings to Movie mode) still clips red unless contrast is set way down. It must be some sort of internal processing I cannot control.
Thanks Everyone!

so, are you using a meter or not? if so, which one?


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post #8 of 9 Old 08-09-2012, 09:29 AM
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The 10-point grayscale controls allow you to set gamma accurately... I would use a target of 2.25. Even if the grayscale looks good, if every step doesn't measure 2.25 gamma, you can fix that with the 10-point controls... and it does help and is worth the investment in time to check and adjust. Don't forget that you can't calculate gamma for 100% or 10% unless you have a reading above 100% and below 10%. So you'll be setting gamma for 20%-90%.

Sounds like you have a meter to use while setting the 2-point grayscale controls, so adding gamma calibration should be easy enough.

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post #9 of 9 Old 08-09-2012, 10:37 AM
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I would add to say that for a night mode, power law gamma can be anywhere from 2.2 to 2.4 (assuming your set has a high enough contrast ratio... if it does not, you'll need to stick closer to 2.2). It also doesn't hurt to use black level compensation if your set's black levels are not stellar.

If you're using BT.1886 gamma, then your black and white levels will determine the exact Y value to target at each of the ten grayscale steps.


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