CurtPalme.com Home Theater Forum

[Neologist]

Hi folks,

the greyscale calibration guide for dummies recently caught my eye.

I just tried to calibrate my Plasma-TV (Panasonic G20) and got the following results:
See files below.

Even though I believe I got quite close to D65 (except for the gamma and the colours´luminances) I have a problem.

When I switch through the test patterns from 0 to 100 IRE everything´s fine, but when looking at a greyscale ladder (with little squares of grey lined in a row from dark to bright and vice versa) some grey shades tend to have a reddish tint.

How can I have tinted greys with a calibrated grey scale?

I used HFCR and an Eye1Display 2.

I followed the guide´s steps and used the AVCHD 709 (with the colour gamut in HFCR set to REC 709).

What did I do wrong?

Besides: would the wrong luminances and the gamma effect the picture very negatively?

I´d be greatful for any help.

Thanks in advance and sorry for my English, but I´m not a native speaker.

Best regards,

Neologist

[akajester]

I'm not an expert but it all looks good to me. The luminance isn't so far off that it would cause an issue in my opinion. I'm not sure what you mean by the reddish tint though.

[Nashou66]

How old is the probe?

Athanasios

[Neologist]

Hey guys,

thanks for the quick answer.

@Nashou66:

The probe is from yesterday.

@Akajester:

I didn´t mean the overall luminance but the primary and secondary colours´luminance.
They´re supposed to match the following:

(compare the 100 IRE Y values of white to those of the colours)

Red 21 %
green 72 %
blue 7 %
yellow 93 %
cyan 79 %
magenta 28 %

In my case that´s:

Red: 20%
Green: 77%
Blue: 8%
Yellow: 97%
Cyan: 79%
Magenta: 25%

I attached another picture of a greyscale ladder below.
What I mean by the reddish tint is that some shades of grey in the picture seem to have a touch of red in them.
Not in this one though, since I just downloaded it somewhere to provide a sample of what I´m talking about.

I´m a little confused.

Thanks again.

Best regards

[Nashou66]

At what two points did you do the calibration at? And how do those two points look on the grey scale? Do they have any red in them?

Athanasios

[HogPilot]

I think you may have misunderstood nashou66 - he was asking how old your i1Display2 is (also referred to as a probe). The filters that it uses to measure RGB can degrade over time and cause drift/inaccuracy in its measurements, which would explain why the the probe is reporting that the greyscale is good even though it is visually obvious that it's not.

[Nashou66]

[Neologist]

Hey,

aaah, thanks a lot. Now I understand.

I did the 2 point calibration at 80% and 30% white.
I´m not sure, if I can tell which shades of grey correspond to 80 and 30 in the testpattern, so I can´t really say if the calibrated shades are free of any tint or not.

But the funny thing is, that when I switch through the patterns from 0 to 100 % (the ones that have a single square in the middle) the colour seems ok, I don´t see those shades.
Only on those ladder-patterns.
Besides: switching to THX-Mode or cinematic mode (i.e. pre-installed picture-modes) results the same, even though the tint is somewhere else and a different colour (for example greenish).

I don´t know how old that probe is. I bought it on eBay and I guess it was a used one (at least I saved € 100 compared to a new one) because I didn´t receice a sales slip.
The device itself and its packing looked pretty good though. All the original stuff was included and didn´t appear to be used a lot.
Besides, I ran i1-Diagnostics prior to calibration and the device passed all the tests.
Guess I should´ve bought a new one.

[Nashou66]

[Nashou66]

One more thing here, because your RGB levels are very good through all IRE's but to you it looks reddish then I'd says its the probe. A good probe would have shown either a low green or a pushed red etc to correspond to what your eyes are seeing.

Athanasios

[akajester]

In the end its your eyes that watch the movie. If it looks a little red back down the red and maybe that's all it takes to fix it. Nashou had some great tips, use a different IRE level to make the adjustments and see if it comes out a little better with your probe. Once you're happy with it write down all the settings so you can go back to them later if you make a mistake.

I have a used i1 and it seems to work good but maybe I got lucky. Or maybe I just don't know enough to know that it should look better!

Another thought, if you were to use that probe to calibrate another tv, would it look too red too? just a thought.

Have fun!

Dale

[HogPilot]

I was thinking about this some more, and if this truly were solely a probe issue where it were delivering inaccurate measurements, then the greyscale should be off across the entire range of 0-100IRE. However, since it measures good at all IREs, looks good at some IREs, and looks reddish at others, this leads me to believe that it's a combination of probe error and display control limitations. In other words, not only is the probe returning erroneous readings, but the greyscale controls built into the TV don't have the resolution to adjust the greyscale finely enough to even it out. However this is just a guess on my part.

I would also recommend getting my hands on another newer or known accurate probe to check your results. A the very least that would tell you whether you're getting proper readings in the first place. I'm not familiar enough with the greyscale controls on your TV to help you if it turns out to be at least partly a problem with your display as well. Good luck!

[Newby217]

[Neologist]

Hi,

well, I kept thinking about this.

I forgot to mention that I used the option "average many reads on dark measurements" in the "measures/sensors" option.
Because, if I uncheck this option my values for red on an 30 IRE pattern vary from 97 to 105 % every one or two seconds.
So when reading the greyscale, I can never tell which value the probe took.
In addition to this, the probe varies in its readings after each calibration (I take the inside of a dvd case and drop a blanket on top to make sure, there´s no additional light). So I guess it´s the probe. Even though I tested it with i1-Diagnostics and it passed all the tests the program had run on it.

Anyway, I kept staring at those greyscale ramps and figure that all the greys appear to have a tint. The darker ones tend to red, the lighter ones to blue.
But actually I´m not that sure, because when I look at a particular one for as long as 1-2 seconds it appears as grey to me.
By the way, it´s the same if I take my calibrated profile or the pre-calibrated out of the box profiles. The only difference is that those tints change their position (they appear in a different shade of grey).
I don´t trust my eyes any more.

I mean, it doesn´t matter that much.
In THX mode the picture is quite awesome.
When I pause a movie and switch to my calibrated profile I sense a change in the picture but I couldn´t tell what exactly changed.
I couldn´t even tell what I would like better, but I would go for whatever the measurements refer to as better.
So I doubt I would even notice those tints while watching a movie.

[Rolls-Royce]

[paintnothing]

Any news on this screen coating causing issues with the calibration? I am soon to be hiring an isf engineer to calibrate my G20. Have tried myself but get bad results in gamma, hdtv test got excellent results using pro1 mode so it should be achievable.

[Elix]

I am at a loss, like Neologist. I have a similar model, TX-PR42GT20 (P42GT25 for Russian market). I calibrated it with ColorHCFR and i1 Display 2 with a help from Greyscale Calibration Guide. I got good results on paper, but the reddish tint is obvious. Which leads me to think that my plasma is impossible to calibrate with i1. >:(
For now I just reduced R-gain and R-offset to reduce the red tint, but I know it ruined everything else.
This topic is currently my only hope. I don't know what calibrator I should get/rent to calibrate it accurately.

[kal]

[kal]

[Elix]

It's not old, it's been bought only 6 months ago.
And thanks for your concern.

[kal]

[kal]