[KMO]

Okay, I'm starting initial investigations on my new Panasonic V10 plasma (in THX mode).

One obvious thing I've noted is that the colours of the display shift depending on input resolution. Changing the output resolution of the Denon DVD-3930 player between SD and HD, you can see both the DVD test pattern changing colour, and more obviously the TV's own menu overlays (including the grey backgrounds) changing colour.

I'm at a bit of a loss to explain what's going on here. I could understand if the DVD-3930 were failing to convert to Rec.709 YCbCr when it upscaled to 720p or higher, or if it just flagged the upscaled YCbCr output as Rec.601 and the TV failed to respect the flag. But it appears that the colours shift between SD and HD even when sending RGB, which shouldn't be affected by this issue (apart from the slight difference in the green primary, but the effect's bigger than that, and that doesn't explain greys changing). And then there are the TV's own menus changing.

It's as if the TV has two different final calibrations for SD and HD inputs. This potentially has a rather big impact on the choice of where to do the upscaling...

I haven't got my colorimeter yet, so no numbers. But can anyone else confirm what I'm seeing? I haven't spotted any visible settings changing, as if it had separate memories for SD and HD.

It's hard to judge the shift in the picture by eye, due to the fairly long blank screen gap between resolution changes, but the warmth of the TV's own grey menus changes nearly as much as a shift from "Normal" to "Warm". Quite significant.

Does anyone have any detailed knowledge of the HDMI behaviour of the kit?

1) Do Panasonic TVs respect the HDMI colorimetry flags C0+C1, or do they always choose 601/709 matrix depending solely on resolution? Or do they not change the matrix at all, and fudge the calibration instead?
2) Does the Denon DVD-3930 convert to Rec.709 YCbCr when upscaling to 720p+? If not, does it set the colorimetry flags to Rec.601?

I'm going to try again later with my other 2 DVD-capable devices to compare results.

[KMO]

Hmm, I think I may be seeing more than one effect here. I can't totally convince myself that the image colours in a well-calibrated display are shifting. But the menu overlays definitely are. And if I turn the colour right down on the TV, there is a big difference in the image.

Looking at the colour bars test (with colour right down) on the HQV Benchmark disc, the "601" area is constant grey for SD resolutions and the "709" area is constant grey for HD resolutions.

My understanding is that the 601 bars have equal luma in Rec.601 (and hence equal luma on the DVD), and the 709 bars are colours that would have equal luma if re-expressed in Rec.709.

I think the player is converting 709 when it upscales to 720p+. Having done so, the "709" bars then have equal luma values when the TV receives them.

Then the looks like TV's colour control operates simply by neutralising the CbCr components of the input signal, regardless of whether that signal is 601 or 709. The fact that the same effect is achieved in RGB suggests that RGB inputs are run via a 601 or 709 YCbCr matrix and back for the colour control's benefit.

Anyway, the upshot of all this is that any adjustment to the colour control outside whatever the "neutral" position is will have different effects depending on whether the input is SD or HD. Could upset calibration slightly, but hopefully nothing major.

I guess the lesson to take here is to get the external kit to scale to HD, so that the TV always receives 709 input, and the colour control always has the same effect, so you achieve the same net calibration. (Of course that has secondary effects, such as the DVD-3930 not supporting full-frame 4:3 output in HD, and TV overscan behaviour).

But none of that explains why the greys shift on the menus. Still not sure if the grey's shifting on the image, I'll have to use a colorimeter to confirm that.