Odd Samsung CMS Behavior - AVS Forum
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post #1 of 10 Old 03-20-2013, 10:38 PM - Thread Starter
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First off, Hello everyone (this is my first post). =)

I have a Samsung UN32EH4000 and I am seeing some discrepancies on how I imagine adjusting a CMS should work and how it actually is working. What I am experiencing is as I move further and further away from 100% luminescence the CMS adjustments have less and less of a effect.

Assuming the CMS controls only adjust the top 30% of luminescence values, is it better to adjust the first 30% or should I leave the CMS controls centered so everything matches?

Below are some graphs using the Green Primary as a example of how the CMS adjustments drift when luminescence goes down:

100% Is perfect, moving closer to 0% the adjustments "wear off" until the primary is back at its "Native" state at 50%:


Calibrated CMS, Green Saturation (50/75/100 Luma):


Now compare 50% from the above graph with the Green pixels Native state, notice
they are almost the same:


Last but not least here is a picture I took comparing the Blue Primary's default settings (0,0,50) with 100% more red (100,0,50). Notice how the CMS adjustments only follow about 35% down:

Source: http://img831.imageshack.us/img831/4377/bluescaletest.png
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post #2 of 10 Old 03-21-2013, 06:45 AM
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Good post, interesting observations. Assuming you've laid all the correct groundwork (movie mode, dynamic enhancements off, other controls calibrated, using full field or APL patterns that would safeguard against any possible dynamic backlight dimming, etc), then it looks like you would get better balanced results by calibrating at 75% sat / 75% luminance. The 100% luminance result may then suffer a bit, but your overall color accuracy should improve.
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post #3 of 10 Old 03-21-2013, 08:04 AM
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Quote:
Originally Posted by ThisIsDugan View Post

First off, Hello everyone (this is my first post). =)

I have a Samsung UN32EH4000 and I am seeing some discrepancies on how I imagine adjusting a CMS should work and how it actually is working. What I am experiencing is as I move further and further away from 100% luminescence the CMS adjustments have less and less of a effect.

Assuming the CMS controls only adjust the top 30% of luminescence values, is it better to adjust the first 30% or should I leave the CMS controls centered so everything matches?

Below are some graphs using the Green Primary as a example of how the CMS adjustments drift when luminescence goes down:

100% Is perfect, moving closer to 0% the adjustments "wear off" until the primary is back at its "Native" state at 50%:

yes, nice plots. You should use the term luminance rather than luminescence. I think what you are seeing is normal non-linear behavior of these displays. You only have 6 points in your "3dLUT" to calibrate and all other points will be interpolated, so the farther you get from your tie points the closer the display will get to native behavior. As Chad suggests you can move the tie points to 75%/75% (saturation/luminance) for example to get better behavior over a larger portion of the gamut.
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post #4 of 10 Old 03-22-2013, 08:54 AM
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Quote:
Originally Posted by ThisIsDugan View Post

First off, Hello everyone (this is my first post). =)

I have a Samsung UN32EH4000 and I am seeing some discrepancies on how I imagine adjusting a CMS should work and how it actually is working. What I am experiencing is as I move further and further away from 100% luminescence the CMS adjustments have less and less of a effect.

Assuming the CMS controls only adjust the top 30% of luminescence values, is it better to adjust the first 30% or should I leave the CMS controls centered so everything matches?

Below are some graphs using the Green Primary as a example of how the CMS adjustments drift when luminescence goes down:

100% Is perfect, moving closer to 0% the adjustments "wear off" until the primary is back at its "Native" state at 50%:


Calibrated CMS, Green Saturation (50/75/100 Luma):


Now compare 50% from the above graph with the Green pixels Native state, notice
they are almost the same:


Last but not least here is a picture I took comparing the Blue Primary's default settings (0,0,50) with 100% more red (100,0,50). Notice how the CMS adjustments only follow about 35% down:

Source: http://img831.imageshack.us/img831/4377/bluescaletest.png

the EH4000 has a CMS? I wasn't aware of any EH series model that does.
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post #5 of 10 Old 03-22-2013, 12:01 PM
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TV's often do not track well across different luminance or saturation levels... which is why the 125-point LUT calibration that Lumagen Radiance processors are now capable of with the right calibration software are so worthwhile... many more points within 3D color space are measured and because different levels of luminance and saturation and hue are measured, intelligent processing can be applied to every color to improve the linearity of response as you move through different luminances and saturations (and hue for that matter, but hue seems to be more "in control" than luminance or saturation tracking on average).

"Traditional" CMS calibration is done at 75% luminance and 100% saturation and those are the only points that get corrected... the corrections applied to those points are applied to everything near them. You only have 6 points where you have proper color. If the TV is non-linear (and they all are to some extent), then the corrections will not be right for other combinations of luminance and saturation (I'm leaving hue out of this as it seems to be less of an issue than the other two, but that doesn't mean it is a NON-issue).

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post #6 of 10 Old 03-22-2013, 03:33 PM
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Quote:
Originally Posted by Doug Blackburn View Post

TV's often do not track well across different luminance or saturation levels... which is why the 125-point LUT calibration that Lumagen Radiance processors are now capable of with the right calibration software are so worthwhile... many more points within 3D color space are measured and because different levels of luminance and saturation and hue are measured, intelligent processing can be applied to every color to improve the linearity of response as you move through different luminances and saturations (and hue for that matter, but hue seems to be more "in control" than luminance or saturation tracking on average).

"Traditional" CMS calibration is done at 75% luminance and 100% saturation and those are the only points that get corrected... the corrections applied to those points are applied to everything near them. You only have 6 points where you have proper color. If the TV is non-linear (and they all are to some extent), then the corrections will not be right for other combinations of luminance and saturation (I'm leaving hue out of this as it seems to be less of an issue than the other two, but that doesn't mean it is a NON-issue).

is 125-point LUT calibration a flawless method (in practice not theory) or can it add artifacts to the picture like banding or something of that sort? I ask because even 10 or 20-point grayscale/gamma controls on consumer displays often don't work as well as they should.
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post #7 of 10 Old 03-22-2013, 11:59 PM - Thread Starter
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Wow this is way more responses than I would see on any other forum. I'm very sorry for all the reading, but all of you deserved a reply.

Quote:
Originally Posted by Chad B View Post

Good post, interesting observations. Assuming you've laid all the correct groundwork (movie mode, dynamic enhancements off, other controls calibrated, using full field or APL patterns that would safeguard against any possible dynamic backlight dimming, etc), then it looks like you would get better balanced results by calibrating at 75% sat / 75% luminance. The 100% luminance result may then suffer a bit, but your overall color accuracy should improve.

Yup I'm in movie mode with all "enhancements" off. 2-point grayscale has a dE of under 2 for all points above 10 IRE and Gamma is between 2.18-2.26. As for full field or APL, the only "enhancement" this display has in Movie mode is it shuts off the backlit when displaying a fully black screen.

Would it not be best for everything to track evenly instead of fixing the values around 75% luma? It's kind of like having a crayon that gives you a different color depending on how hard you press.

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Originally Posted by zoyd View Post

yes, nice plots. You should use the term luminance rather than luminescence. I think what you are seeing is normal non-linear behavior of these displays. You only have 6 points in your "3dLUT" to calibrate and all other points will be interpolated, so the farther you get from your tie points the closer the display will get to native behavior. As Chad suggests you can move the tie points to 75%/75% (saturation/luminance) for example to get better behavior over a larger portion of the gamut.

Thank HCFR for the plots. wink.gif

Luminance, got it.

Why 75% Saturation? I though you're supposed to set Primary/Secondary colors with 100% saturation?

Speaking of HCFR, thank-you for keeping it up to date.

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Originally Posted by PlasmaPZ80U View Post

the EH4000 has a CMS? I wasn't aware of any EH series model that does.

In the factory menu, All the EH Series have:
  • Four 2-point Grayscale temperatures adjustments (Cool, Standard, Warm1, Warm2)
  • Separate contrast adjustments for each Color Temperature
  • Two 6-point CMS modes (Native, Auto)
  • Two 6 point saturation adjustments (Native, Auto)
  • Skin Hue, Skin Saturation
  • 2 Gamma adjustments (1 in decimals, another in whole numbers)
  • Y/C Delay Adjustments
  • Audio Delay Adjustments

All the controls work as expected except for the CMS. I see you have a EH6030, If you like I could see if I can get you the IR codes for the factory menu and also document all the menu controls I'm sure of.

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Originally Posted by Doug Blackburn View Post

.."Traditional" CMS calibration is done at 75% luminance and 100% saturation and those are the only points that get corrected... the corrections applied to those points are applied to everything near them. You only have 6 points where you have proper color. If the TV is non-linear (and they all are to some extent), then the corrections will not be right for other combinations of luminance and saturation (I'm leaving hue out of this as it seems to be less of an issue than the other two, but that doesn't mean it is a NON-issue).

I've tried doing the calibration at 75% and 100% luminance but that doesn't help because the CMS only effects the first 80 brightness levels (35%). As you drift towards black, it has no effect at all! I could set every control to 100,100,100 and it doesn't change anything after you go down to about 50% luma.


I know that this is a low end model (EH4000) which might explain the odd behavior of the CMS controls. But what I don't understand is, if the controls don't work why were they included in the first place? Not only that but why were they adjusted from the factory. Maybe they figure those are the only points reviewers measure. o_0

My question is, how important are the first 80 or so values (155-235)? Should I bother to set the CMS if its only going to effect that small portion? (Remember, the adjustments fade so all 80 values don't get the same adjustment. - See the blue picture in the first post) And if I do set it, should I adjust the xyY of the colors or only the Y?


P.S. How bad of a idea would it be to use a saturation control to increase the luminance of a Blue primary that reads 16% too dark (White: 109.704, Blue: 6.641)?
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post #8 of 10 Old 03-23-2013, 08:36 AM
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I can't answer all your questions but I know this from forum memebers who have done some extensive testing and pro's. 75%amplitude/75% saturation is the way too go if the set doesn't track well across the color space. For the D series samsungs 75/75 is the best compromise it will make the gamut track the colors better at lower saturations but 100% will be over saturated it's a trade off. Most content lies in the 75% realm. Sometimes because they give you a control on a tv doesn't mean it will function like it should ....
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post #9 of 10 Old 03-23-2013, 09:02 AM
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post #10 of 10 Old 03-23-2013, 11:24 AM
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Quote:
Originally Posted by PlasmaPZ80U View Post

is 125-point LUT calibration a flawless method (in practice not theory) or can it add artifacts to the picture like banding or something of that sort? I ask because even 10 or 20-point grayscale/gamma controls on consumer displays often don't work as well as they should.

Nothing is flawless - that's impossible... at a price anyone is willing to pay.

Eliminating as many flaws as possible is the best we can do. Reducing the magnitude and impact of the residual flaws is the next-best thing you can do. With 125-point LUTs you accomplish both... far fewer residual flaws than "old" calibration methods.

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