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post #1 of 43 Old 05-06-2012, 03:22 AM - Thread Starter
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Hello
I've been reading the guide tom huffman calibration and does not indicate how to adjust the backlight. Elsewhere I read that backlight and contrast controls light output, but I do not know the correct method to adjust the light output using the backlight and contrast controls. ¿Someone could explain me, please?

If I can get a light output of 35 ftL using backlight and contrast. Which of the two I use? Is indifference setting the other?

Another question. When we calibrate a TV full local dimming LED ¿must be turned on or off?

Thank you very much for responding.
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post #2 of 43 Old 05-06-2012, 05:35 AM
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Brightness and Contrast are the setting that effect the video signal. Backlight is just that, it is a light behind the LCD crystals that allow you to see the image. The source of the light is CCFL or LED. There are probably several variances on the process since not all Displays respond the same, but the general idea is to reduce back light to 30% or 50% of it's adjustment range.
Then adjust Brightness and contrast to achive the highest light output without discoloration or clipping. Then use the backlight to fine tune the light output.
Recheck brightness and contrast after backlight is set.

The recommendation that I has been given to me by others, is turn off LD if you can and if not use Full Fields.
If you take a max light reading at 100% with a window and then change to full fields and the output changes drastically, there is still processing going on.. Gamma will be way weird! Good luck!
Hope that helps.

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post #3 of 43 Old 05-06-2012, 05:47 AM
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Quote:
Originally Posted by electroFan View Post

Hello
I've been reading the guide tom huffman calibration and does not indicate how to adjust the backlight. Elsewhere I read that backlight and contrast controls light output, but I do not know the correct method to adjust the light output using the backlight and contrast controls. ¿Someone could explain me, please?

If I can get a light output of 35 ftL using backlight and contrast. Which of the two I use? Is indifference setting the other?

Another question. When we calibrate a TV full local dimming LED ¿must be turned on or off?

Thank you very much for responding.

Here's what I generally do:
-Set contrast as high as possible without clipping any colors (check with AVS or Spears & Munsil disks)
-Set backlight to get desired output (100% white field, 35-50fL), lower backlight level will generally result in better deep blacks
-Adjust brightness (black level) with AVS pattern or meter using 0% white field (ie black)
-repeat/recheck (the controls interact)
-also redo when adj greyscale, cms, gamma

Hope this helps
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post #4 of 43 Old 05-06-2012, 08:05 AM - Thread Starter
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airscapes and T3b_vat A lot of thanks
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post #5 of 43 Old 05-07-2012, 08:48 AM
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Lower backlight settings produce darker blacks. In a perfect world, you'd set the backlight at it's lowest possible setting and get the light level you need (30-35 fL in a dark room is fine) with Contrast.

In the real world, the Contrast control may blow-out highlight detail if set too high so you have to check bright steps with a test pattern that will show if you are crushing highlight steps (say digital 220-254). A lot of people think it's blasphemy to crush steps in the range of 236-254, but, honestly, there's no image detail at those levels, you only get "specular highlights" up there... reflections from chrome, water, crystal chandeliers, etc. I doubt there are many people who can "see" any difference in images where steps above 235 are crushed. But you DO NOT want to crush any steps below 235, ever.

The other real-world issue is that on some TVs when you use very low backlight settings, the color balance can get very odd because the backlight (LED or fluorescent) has a significant color shift at low output levels, so you have to watch out for that also. I often calibrate 100% white with the backlight set in the middle of it's range, then decrease the backlight to it's lowest setting and remeasure 100% to see how much of a shift there is. If the shift is minor and can be corrected with the TV's CMS controls, the lowest setting could be usable if Contrast goes high enough to get you to 30-35 fL. It's a balancing act. You may find you have to increase the backlight setting 1 or 2 or more steps to get Contrast into a usable range. There's a lot of variation from brand to brand and model to model.

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post #6 of 43 Old 05-07-2012, 09:22 AM
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Thanks Doug!
I wondered why I had read that changing the back light to much or setting it to low could mess with the gray scale and color, but don't ever recall an explanation as to why. Thanks for that and the tip on checking for the color shift, make perfect sense!

Doug

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post #7 of 43 Old 05-14-2012, 05:56 AM - Thread Starter
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Could anyone explain what is the method for adjusting cell light in plasmas? Please
Thanks in advance
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post #8 of 43 Old 05-14-2012, 07:40 AM
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like above, set it to a mid-range and then get contrast as high as you can without clipping 235 and below (255 if you're a purist). On plasmas you have to watch out that one color doesn't clip before another, you will see that as a color shift in peak white. After contrast is set, adjust cell light for 30-35 ftL, you don't have to worry about color shifts when adjusting cell light.

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post #9 of 43 Old 05-14-2012, 09:40 AM
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Quote:
Originally Posted by zoyd View Post

like above, set it to a mid-range and then get contrast as high as you can without clipping 235 and below (255 if you're a purist). On plasmas you have to watch out that one color doesn't clip before another, you will see that as a color shift in peak white. After contrast is set, adjust cell light for 30-35 ftL, you don't have to worry about color shifts when adjusting cell light.

does cell light behave more like a contrast control or more like an LED/LCD backlight control? obviously this setting is only on Samsungs and not LG or Panasonic Plasmas.


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post #10 of 43 Old 05-14-2012, 10:23 AM
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contrast maps input codes to DSP codes so it's an A/D or D/D gain control. cell light is applied after this conversion and scales the amount of time the pixel is on during PWM, so it behaves in a similar fashion to an led backlight control (light valve). The corollary control in panasonics is called panel brightness (3 settings), I think LG just calls it backlight on their plasmas.

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post #11 of 43 Old 05-14-2012, 12:04 PM
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Quote:
Originally Posted by zoyd View Post

contrast maps input codes to DSP codes so it's an A/D or D/D gain control. cell light is applied after this conversion and scales the amount of time the pixel is on during PWM, so it behaves in a similar fashion to an led backlight control (light valve). The corollary control in panasonics is called panel brightness (3 settings), I think LG just calls it backlight on their plasmas.

then does cell light have any effect on black level?


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post #12 of 43 Old 05-14-2012, 01:27 PM
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as in mll black level? no. It will raise the luminance of near black.

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post #13 of 43 Old 05-14-2012, 01:33 PM
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Quote:
Originally Posted by zoyd View Post

as in mll black level? no. It will raise the luminance of near black.

then is it sort of a gamma control as well? or just a white level/contrast/picture control?


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post #14 of 43 Old 05-14-2012, 01:38 PM
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It's not supposed to, it scales each level by the same proportion so gamma should be constant. In practice I don't know how well that holds for near black.

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post #15 of 43 Old 05-14-2012, 01:42 PM
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Quote:
Originally Posted by zoyd View Post

cell light is applied after this conversion and scales the amount of time the pixel is on during PWM, so it behaves in a similar fashion to an led backlight control (light valve).

Regarding LED/LCD backlight controls, don't those affect the brightness of the backlight directly and not how much passes through the LCD panel? So, not really a light valve but more of a backlight brightness control?


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post #16 of 43 Old 05-15-2012, 09:16 AM
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Quote:
Originally Posted by electroFan View Post

Could anyone explain what is the method for adjusting cell light in plasmas? Please
Thanks in advance

The only right setting for Samsung's cell light control is the highest setting. All other settings cause more pixel flickering, especially at lower luminance levels. It's a "baloney" control, like Sharpness. It is completely non-useful for anything. The only reason cell light even exists is so that Samsung can have the same menu structure for LCD and plasma TVs. The cell light control simply occupies the space for the LCD backlight control. If it NOT a control that will improve the image, but it does degrade the image if you set it below the maximum setting.

This comes from someone who knows the function of the cell light control who is an "insider" at Samsung. The only right setting for the Sharpness control is the one that turns it off (and that may or may not be zero, you have to use a pattern to know). When Samsung plasmas had no cell light control, they operated as if there was a cell light control set to the maximum setting -- as do all brands of plasma panels that don't have a cell light control. In the early years of the cell light control, setting it below maximum seriously compromised gamma, but Samsung finally tuned that defect out and now the control isn't completely evil, but it doesn't do anything useful either so just set to max and leave it alone, never to be thought about again.

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post #17 of 43 Old 05-15-2012, 10:18 AM
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Quote:
Originally Posted by Doug Blackburn View Post

The only right setting for Samsung's cell light control is the highest setting. All other settings cause more pixel flickering, especially at lower luminance levels. It's a "baloney" control, like Sharpness. It is completely non-useful for anything. The only reason cell light even exists is so that Samsung can have the same menu structure for LCD and plasma TVs. The cell light control simply occupies the space for the LCD backlight control. If it NOT a control that will improve the image, but it does degrade the image if you set it below the maximum setting.

This comes from someone who knows the function of the cell light control who is an "insider" at Samsung. The only right setting for the Sharpness control is the one that turns it off (and that may or may not be zero, you have to use a pattern to know). When Samsung plasmas had no cell light control, they operated as if there was a cell light control set to the maximum setting -- as do all brands of plasma panels that don't have a cell light control. In the early years of the cell light control, setting it below maximum seriously compromised gamma, but Samsung finally tuned that defect out and now the control isn't completely evil, but it doesn't do anything useful either so just set to max and leave it alone, never to be thought about again.

Hi Doug,

Have you tested this on the whole range of models to see if it acts the same, B-E? I'm just curious because I have a C8000, and I've never set the cell light above 18 while calibrating. I will definitely try this method out, and test the results. I always love an excuse to re-calibrate my display.

Thanks
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post #18 of 43 Old 05-15-2012, 10:41 AM
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cell light between 11-14 w/contrast @95 (28-35 ftL) does not generate any additional flickering at low luminance on my d-series display.

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post #19 of 43 Old 05-16-2012, 08:53 AM
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Quote:
Originally Posted by zoyd View Post

cell light between 11-14 w/contrast @95 (28-35 ftL) does not generate any additional flickering at low luminance on my d-series display.

That doesn't make anything but the highest setting the right setting. As mentioned before, a Samsung insider (a technical person, not a marketing/sales person) said the highest setting is the right setting. Period. There's zero advantage to using a lower setting. And also as mentioned earlier, this is a baloney control with no useful function other than to fill a slot in the menu structure and give Samsung something to tout that nobody else has. Like a 6th finger or a third nipple.

If there was no cell light control, the TVs would be operating with the equivalent of the highest menu setting because that is the right setting. Contrast should be lower than 95... typically in the 80s which is where you're likely to be with cell light set to max.

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post #20 of 43 Old 06-02-2012, 10:05 AM
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Quote:
Originally Posted by Doug Blackburn View Post

That doesn't make anything but the highest setting the right setting. As mentioned before, a Samsung insider (a technical person, not a marketing/sales person) said the highest setting is the right setting. Period. There's zero advantage to using a lower setting. And also as mentioned earlier, this is a baloney control with no useful function other than to fill a slot in the menu structure and give Samsung something to tout that nobody else has. Like a 6th finger or a third nipple.

If there was no cell light control, the TVs would be operating with the equivalent of the highest menu setting because that is the right setting. Contrast should be lower than 95... typically in the 80s which is where you're likely to be with cell light set to max.

ok, now I'm a believer! I had always done the opposite, set contrast in the mid-90s primarily so that the 10 pt control aligned well with each stimulus level. I then dialed cell light down to get my desired peak white level. I had checked as you suggested for side effects of a lower than max cell light setting (PWM noise, etc.) but hadn't found any...until yesterday. I was playing around with full field patterns and noticed a peculiar effect related to cell light.

Given two identical windowed peak white combinations on my plasma:

1. Cell light 14, Contrast 95 - 10% window,100% stim = 35 ftL
2. Cell light 20, Contrast 82 - 10% window,100% stim = 35 ftL

Case 1 full field, 100% stim = 8.5 ftL
Case 2 full field, 100% stim = 12 ftL

So anyone using less than max cell light on a samsung plasma will be increasing the effect that the ABL has at high picture levels.

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post #21 of 43 Old 06-02-2012, 10:08 AM
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they should just make cell light a placebo control that doesn't nothing other than occupy the backlight slot in the picture menu


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post #22 of 43 Old 06-04-2012, 11:24 AM
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Originally Posted by zoyd View Post

ok, now I'm a believer! I had always done the opposite, set contrast in the mid-90s primarily so that the 10 pt control aligned well with each stimulus level. I then dialed cell light down to get my desired peak white level. I had checked as you suggested for side effects of a lower than max cell light setting (PWM noise, etc.) but hadn't found any...until yesterday. I was playing around with full field patterns and noticed a peculiar effect related to cell light.

Given two identical windowed peak white combinations on my plasma:

1. Cell light 14, Contrast 95 - 10% window,100% stim = 35 ftL
2. Cell light 20, Contrast 82 - 10% window,100% stim = 35 ftL

Case 1 full field, 100% stim = 8.5 ftL
Case 2 full field, 100% stim = 12 ftL

So anyone using less than max cell light on a samsung plasma will be increasing the effect that the ABL has at high picture levels.

Hello , man I am amazed that you guys, specially you Zoyd keep making new discoveries about calibrating the samsung plasma d series. Perhaps that guide for calibrating with hcfr should be updated to mention this new information, well atleast it's new to me, what's next??? LOL
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post #23 of 43 Old 06-04-2012, 11:54 AM
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Quote:
Originally Posted by zoyd View Post

ok, now I'm a believer! I had always done the opposite, set contrast in the mid-90s primarily so that the 10 pt control aligned well with each stimulus level. I then dialed cell light down to get my desired peak white level. I had checked as you suggested for side effects of a lower than max cell light setting (PWM noise, etc.) but hadn't found any...until yesterday. I was playing around with full field patterns and noticed a peculiar effect related to cell light.

Given two identical windowed peak white combinations on my plasma:

1. Cell light 14, Contrast 95 - 10% window,100% stim = 35 ftL
2. Cell light 20, Contrast 82 - 10% window,100% stim = 35 ftL

Case 1 full field, 100% stim = 8.5 ftL
Case 2 full field, 100% stim = 12 ftL

So anyone using less than max cell light on a samsung plasma will be increasing the effect that the ABL has at high picture levels.

10% window or 10% APL window?
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post #24 of 43 Old 06-04-2012, 12:32 PM
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10% area window

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post #25 of 43 Old 06-04-2012, 07:44 PM
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Quote:
Originally Posted by kjgarrison View Post

10% window or 10% APL window?

Quote:
Originally Posted by zoyd View Post

10% area window

So you don't use APL windows for grayscale calibration? I thought we were supposed to use APL windows for our plasma grayscale cal. I wonder what your comparison would look like if you had used APL windows.
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post #26 of 43 Old 06-04-2012, 07:59 PM
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That test was not part of calibration, just a quick test to demonstrate that given settings that generate equal peak whites when the ABL is not active yield much different full field peak values depending on cell light value. This puts to bed electrofan's question about the effects of the cell light control.

As far as APL patterns for plasma calibration it doesn't matter (much) what you use for grey scale or color, APL or 10-18% windows will give you very similar results. For gamma however, I recommend APL patterns on samsungs to mitigate the variable gamma inherent in the driving scheme.

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post #27 of 43 Old 06-04-2012, 08:19 PM
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Quote:
Originally Posted by zoyd View Post

That test was not part of calibration, just a quick test to demonstrate that given settings that generate equal peak whites when the ABL is not active yield much different full field peak values depending on cell light value. This puts to bed electrofan's question about the effects of the cell light control.

As far as APL patterns for plasma calibration it doesn't matter (much) what you use for grey scale or color, APL or 10-18% windows will give you very similar results. For gamma however, I recommend APL patterns on samsungs to mitigate the variable gamma inherent in the driving scheme.

Yeah, we have the same TV, you and I.
I do my grayscale and gamma at the same time. I don't know if HCFR has this functionality or not. I use Chromapure, and it does. I'm still waiting to be able to use my D3 probe's corrections in HCFR.
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post #28 of 43 Old 06-05-2012, 03:43 AM
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yes, you can do them at the same time in HCFR. May I ask why you would use it over Chromapure?

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post #29 of 43 Old 06-06-2012, 08:45 PM
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Quote:
Originally Posted by zoyd View Post

yes, you can do them at the same time in HCFR. May I ask why you would use it over Chromapure?

Gawd, I had AWS! (AVS withdrawl syndrome)

I like Chromapure's ease of use. I used HCFR before and am curious to see how it has evolved. I want to see if I get the same measurements from the two products. Basically to 'validate' the results, and if they differ try to figure out which one is "right." Also, the low IRE measurements, where the D3 is supposed to be superior, jump around a lot, and I want to see if that is consistent.
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post #30 of 43 Old 06-12-2012, 05:25 PM
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Zoyd or Doug: Thanks for all this info. it really is helpful. I have a 64d7000 and i have always had my cell light to 20 and contrast to 95. This is what my calibrator set it to also. Are you saying that the contrast should be down to 82 now? Will that yield a better picture? I'm just not sure what i should do with some of the other controls....namely brightness and gamma. Any help would be greatly appreciated.
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