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Weak Power Supply vs. Bad Calibration Technique vs. ???

1928 Views 3 Replies 3 Participants Last post by  mhutchins

I recently purchased my first Plasma after years of CRT-based displays; a Panasonic TC-P50V10. I just love the picture, but I wanted more. First I broke in the set using the appropriate colored images and settings. Then I applied the CNET settings and liked the picture even better, but I wanted more. So, I bought an Eye 1 Display LT to calibrate the set. I practiced making adjustments only in the user menu's, and I liked the picture even better, but I wanted more. So I'm about to embark on adjusting the service menu settings, but a recent thread by ORTA sparked a question about my experience to date.


While adjusting the gamma curve, I saw a huge difference in the gamma curve between using full fields vs. low average picture level ("APL") patterns. At higher luminance levels, the gamma curve just tanked. The display could not keep pumping out more lumens as the luminance increased when displaying full screen whites. Without changing any settings, just using a different APL test pattern, the gamma curve looked more appropriate.


1. Is this normal behavior for a plasma, or am I doing something wrong?

2. If it's normal, or at least common, what is the best pattern to use when adjusting the gamma curve to compensate for this behavior (I'm using Color HCFR with the AVS HD 709 DVD in a Sony PS3 for my source and HDMI for all signal paths)?

3. If this behavior is true for gamma testing, would similar artifacts be introduced into the color/gray scale dimensions during calibration with high APL patterns vs. low APL patterns? If so, what are the best patterns to use with the Eye 1 sensor?


Back in the CRT days, I think I remember specific test patterns that stressed the power supply with large white fields to determine how well the set could maintain light output in small vs. large areas of white. My recollection was that diminishing light output with increasingly larger white areas was an indication of a power supply with inadequate capacity.

Do I have a weak power supply in my new plasma, or am I just proving the severity of my dementia?
And before you say that rarely will you have full screen whites, let me add that I like to watch a lot of hockey...

Thanks for your input.

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Set up the TV to do two modes then. The TV can do that. One for everything else ... and one for Ice Hockey sheets of ice. Does not apply on the close up shots when grinding along the boards ... or the other 60% of the broadcast that isn't all white.

Or go with an LCD set and not worry about this ... but then complain about the motion problems ... sigh ...

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It is normal for plasma displays to get "less bright" as you fill more and more of the screen with white. If you advance the Contrast control too much (say for a daytime viewing mode), you can even "run out of gas" in one color (red, green, or blue) before the other colors on some plasmas - and of course that will lead to color-tinted whites when you crank the Contrast that high. You can use your meter and software to determine whether you have that issue with your TV - but the software will need to show you luminance curves for all 3 colors at the same time (easy enough with grayscale measurement data but not all software shows you this info - in graph form).

Always calibrate plasmas with window patterns - and the window should fill about 10% of the screen area (rather than 25% or some larger %).

Even though the peak white level goes down when the screen is full of white, the total amount of light emitted by the panel still increases and that's enough to somewhat compensate for the lower peak level - but hockey fans do tend to notice the picture is not as brilliant as it is on LCD displays. It may make you feel better to think of the full-field dimming as a secondary means of preventing eyestrain when viewing hockey in a dark room... of course if you aren't in a dark room that doesn't help :)
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Thanks, Guys.

I will check the size of the window patterns I'm using for calibration. When hockey season starts up again, I will definitely create a mode for hockey.

Thanks for the tips!

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