Does Black Level on a Plasma TV Get Worse Over Time ???

I don't know why the black level would be getting worse. You would think it would remain constant while the brightness fades...

This seems counterintuitive to me too. I think I would be curious to know the details of your test methods. What sensor are you using? How are you running this test? Are the test conditions identical each time? Some sensors are not great at low luminance levels, and of course, dark readings can be vastly affected by the conditions in which the readings are taken. Just a thought.

Look at Tom Huffman's posts concerning black level over at the Panasonic PZ80/PZ85 Owners Thread.

It's kinda hard to know that other people's settings are...

Setting a reference in this situation is quite difficult.

Dimitri

Hi fernando,

Do you mean luminance levels for a given brightness setting?.

Most of the low cost filter based colorimeters available will not provide accuracy for "Y" below .06 fL at best. Anyone that provides values that are at this level or below should be suspect of the accuracy of the data to begin with. Just because the software reports a value does not mean that it is an accurate value.

I'm seeing the same behavior on my 58" PZ800U after 540 hours, measuring with an EyeOne DisplayLT. When it had just about 150 hours on it it was measuring consistently at 0.008 ftL but now it's measuring 0.014 ftL.

I'm seeing something very similar with my 50px80. While I don't have the calibration equipment to accurately measure luminance, I can say that the deepest black (channel or hdmi with no input) has been noticeably brightening over time. I'm at about 1000 hours now.

Found my way into this thread researching if this was a normal phenomenon.

To me it would seem a difference of +-0.012 FtL would be well within the range of error with that meter, especially at that low of a grayscale level. Heck, anything below 10% gray, for most displays, is generally too inaccurate to take into consideration, so why would you accept readings below 0.5 FtL? I believe it is quoted to go to 0.06 FtL, but i still wouldn't trust the accuracy of a +-0.012 fluctuation.

I disagree. The EyeOne Display LT is inaccurate reading RGB levels at 0% gray but it does a fine job with luminance levels. It is also very consistent and was showing the same consistent levels when the set was relatively new. In fact, a second EyeOne (brand new) measured the same 0.008 ftL. Now that meter is reading 0.014 ftL.

Even if you discredit the EyeOne Display meter's readings, then what about Tom Huffman's findings with more expensive/more accurate probes? See his post here: http://www.avsforum.com/avs-vb/showt...4#post16248154

I'm not here to argue Tom's post (although the thread is anything but concrete).
I was just mentioning that the eye one really is not that accurate at those FtL levels. This comes from experience with 2 different i1d2's and calman. This is especially true when measuring plasma's, which are inherently buggy with all but true spectrophotometers.

The only way to know if an instrument is returning accurate results (luminance or color) is to compare it against a known reference.

I have checked the luminance of the X-Rite colorimeters using a Minolta LS-100 as the reference on a 9th generation Kuro.

	Minolta LS-100		Chroma 5			Display 2
%stim	cd/m2	fL	cd/m2	fL	% error	cd/m2	fL	% error
10.0	0.647	0.189	0.652	0.190	0.77%	0.647	0.189	0.00%
9.0	0.526	0.154	0.520	0.152	-1.14%	0.526	0.154	0.00%
8.0	0.409	0.119	0.410	0.120	0.24%	0.408	0.119	-0.24%
7.0	0.276	0.081	0.285	0.083	3.26%	0.284	0.083	2.90%
6.0	0.201	0.059	0.202	0.059	0.50%	0.21	0.061	4.48%
5.0	0.165	0.048	0.172	0.050	4.24%	0.174	0.051	5.45%
4.0	0.131	0.038	0.132	0.039	0.76%	0.138	0.040	5.34%
3.0	0.091	0.027	0.091	0.027	0.00%	0.091	0.027	0.00%
2.0	0.015	0.004	n/a	n/a	n/a	n/a
1.0	0.007	0.002	n/a	n/a	n/a	n/a
				Ave. Error	1.37%		Ave. Error	2.30%

As you can see, the luminance readings of both the Chroma 5 and the very inexpensive Display 2 are quite accurate down to their rated level of 0.05 cd/m2. Actually, they seem to go just a little lower than this--I'd say 0.04 cd/m2.

Getting good luminance readings at reasonably low light levels does not require expensive equipment. It is certainly more problematic with color, especially with certain types of displays.

Regarding the Panasonics, all I can say is that the black level of my 85U has about doubled from initial purchase to around 2200 hrs. of use. I have also calibrated several 85Us and 800Us and I get very consistent black level readings in the 0.010-0.015 fL range. These are snapshots with varying number of hours on the panels, but none were just out of the box (which is when I took the initial reading on my panel) and all had considerably less than 2200 hrs, which is why the the readings are somewhere in between the two extremes I measured on my 85U.

my panasonic 11G pro plasma was .011 when i bought it and .011 now. service menu says 1010 hours.

[display one LT, HCFR, AVS HD 709]

I can add to the database of rising black levels. My panny 50PH10UK used to measure 0.034 fL or so over a year ago when I first got it and calibrated (using HCFR and i1 D2)... nowadays it's around 0.050 fL.

I had thought that my black levels were getting worse, subjectively, but chalked it up to selective memory... then I saw one of Tom's posts on this subject and went back and checked my data from old saved HCFR runs, and discovered that my subjective assessment had some amount of quantitative backing...

not too happy about it, as these Panny's don't have a lot of black level to spare

incidentally, my 10UK is getting worse and worse "purple snakes" over time as well.... I'm wondering if the two phenomena are related (e.g. improper voltage regulation from a failing board?)

Is this brightness problem something we can expect on all plasma brands?

since we don't even know for sure it is a REAL problem (although we have scattered evidence), I don't know how you could expect anyone to draw generalized conclusions across all brands.

Im just nervous for my dear Kuro-500M. thats all..

Your 500M will get darker over time. Take a reading at 150 hours, then 500 hours, and finally 1000 hours.

I trust your words, d-nice. Unfortunately I dont have the equipment for taking readings. Just my eyes...

Does this apply to the 9g elites as well?

stupid thing....Lg agressive plasma goes darker and darker after 1000 hours !!