Interaction with Grayscale and Gamma on a Panasonic PZ80U - AVS Forum
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post #1 of 8 Old 07-14-2009, 09:55 AM - Thread Starter
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I've recently done a grayscale calibration on my Panasonic PZ80U with an i1d2 and ColorHCFR. I have left green cut at the default 80 and green drive at the default (and max recommended) FC. My question is not about grayscale itself but rather how grayscale controls affect gamma.

I've discovered that keeping the picture setting low (30 ftL) produces higher gamma than when it is set higher. The same holds true for brightness; however, lowering brightness too much results in black crush. So, I'm wondering if lowering or increasing green cut and then compensating with the brightness control to avoid black crush or gray blacks can increase gamma in the same way lowering brightness does, except without the black crush?

(Of course, I would maintain D65 throughout the grayscale when doing all of this.)

There also exists the sub-brightness control in the SM but I don't know if that is any different from the standard brightness control in the user menu in terms of it's effect on gamma and black crush/clipping.
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post #2 of 8 Old 07-14-2009, 09:59 AM
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Greetings

You do know that cuts and drivers are brightness and contrast controls, right?

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post #3 of 8 Old 07-14-2009, 10:08 AM - Thread Starter
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Yes, I know that cuts and drives are essentially RGB brightness and contrast controls but does that mean they work exactly the same way as regular brightness and contrast controls or is there at least some difference in how they operate with respect to my earlier question?
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post #4 of 8 Old 07-14-2009, 10:50 AM
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Quote:
Originally Posted by PlasmaPZ80U View Post

Yes, I know that cuts and drives are essentially RGB brightness and contrast controls but does that mean they work exactly the same way as regular brightness and contrast controls or is there at least some difference in how they operate with respect to my earlier question?

If you adjusted all three RGB cuts by the same amount, that would be essentially the same as adjusting the Brightness control. If you adjusted the green cut by itself that would throw off the white balance at the lower end of the grayscale.

The sub-brightness control in the SM is just an offset that establishes the operating range of the Brightness control. The only reason to use it is if you find that the Brightness control has an insufficient range of operation (it is fine on the Pannys) or if you wanted to set brightness in the service menu while leaving the user control at zero as a way of making it easier to return to a calibrated state if it ever gets screwed up.

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post #5 of 8 Old 07-14-2009, 01:08 PM - Thread Starter
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So, in short, are you saying that there is no way to raise gamma if I want to maintain a light output of 30 ftL and a brightness just high enough to avoid black crush (without any external help)?
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post #6 of 8 Old 07-14-2009, 02:24 PM
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Quote:
Originally Posted by PlasmaPZ80U View Post

So, in short, are you saying that there is no way to raise gamma if I want to maintain a light output of 30 ftL and a brightness just high enough to avoid black crush (without any external help)?

Yes. You could do what you describe with an external processor, like the Lumagen, that offers gamma adjustments at each step along the grayscale.

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post #7 of 8 Old 07-15-2009, 10:46 PM
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You've encountered the main limitation of most Panasonic displays - though I have to say the current _10 models are not as bad as Panasonics from years past. It's disappointing that Panasonic has not stepped up with gamma and CMS controls when Samsung (many models) and Toshiba (a few models) both offer them. Pioneer tried to offer them before stopping display manufacturing, but choked on their CMS controls and have a very limited gamma range adjustment.

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post #8 of 8 Old 07-15-2009, 11:51 PM
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The V10 models offer several gamma curves in CUSTOM mode, though they are not directly adjustable.

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