CalMAN 5 - RGB Balance / Gamma Issue - Panasonic GT30 / i1Display Pro - AVS | Home Theater Discussions And Reviews
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post #1 of 17 Old 06-25-2014, 06:57 PM - Thread Starter
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CalMAN 5 - RGB Balance / Gamma Issue - Panasonic GT30 / i1Display Pro

I'm trying to diagnose an issue I'm seeing in a recent calibration of my Panasonic GT30 with CalMAN 5 Enthusiast. I'm using a two point calibration (30 IRE and 80 IRE), and can get the RGB balance within3 dE, but am experiencing a weird overall RGB curve across 0-100 IRE:



Can anyone help me understand why I'm seeing this behavior? I'm using Custom picture mode, Warm 2, 2.2 Gamma, with all the "extra" picture settings disabled.

The gamma curve drops off substantially at 30 IRE:



Is this an issue with my set, or potentially with my meter (i1Display Pro)?

Any help is greatly appreciated.
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post #2 of 17 Old 06-25-2014, 07:36 PM
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This is not at all unusual with two-point grayscale adjustment systems. The effects of adjustments at 30 and at 80 usually overlap, so increasing brightness at both ends will add up together and boost the middle. Because your gamma is at its worst at 80, I'd start by decreasing all 3 colors at 80 percent to cut brightness there (one or two clicks each color, then measure the whole range, repeating until you've reached a balance across the range). You may have to give up a perfect D65 in order to reach dEs of 3 or less across the range and a decent gamma curve.

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Last edited by Rolls-Royce; 06-25-2014 at 07:56 PM.
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post #3 of 17 Old 06-25-2014, 10:02 PM
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What is your pattern source and size of the window? Seems like a case of ABL as the 30 series had a more aggressive ABL that required one to use small windows.
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post #4 of 17 Old 06-25-2014, 10:47 PM
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HDMI content type needs to be switched to "graphics" and gamma to 2.4. The GT and ST30s were both that way.

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post #5 of 17 Old 06-26-2014, 07:09 AM - Thread Starter
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Quote:
Originally Posted by venkatesh_m View Post
What is your pattern source and size of the window? Seems like a case of ABL as the 30 series had a more aggressive ABL that required one to use small windows.
I'm using the AVS HD 709 disc with the CalMAN Windows patterns. Also to note - this set has never had the fluctuating brightness fix.

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HDMI content type needs to be switched to "graphics" and gamma to 2.4. The GT and ST30s were both that way.
Thanks Chad - I'll give that a shot.
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post #6 of 17 Old 06-26-2014, 07:12 AM - Thread Starter
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Quote:
Originally Posted by Rolls-Royce View Post
This is not at all unusual with two-point grayscale adjustment systems. The effects of adjustments at 30 and at 80 usually overlap, so increasing brightness at both ends will add up together and boost the middle. Because your gamma is at its worst at 80, I'd start by decreasing all 3 colors at 80 percent to cut brightness there (one or two clicks each color, then measure the whole range, repeating until you've reached a balance across the range). You may have to give up a perfect D65 in order to reach dEs of 3 or less across the range and a decent gamma curve.
Sorry - missed this in the multi-quote. Appreciate the advice. I'll give this a shot as well if I'm still seeing this behavior after implementing Chad's fixes below.
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post #7 of 17 Old 06-26-2014, 08:21 AM
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Quote:
Originally Posted by drangel1 View Post
I'm trying to diagnose an issue I'm seeing in a recent calibration of my Panasonic GT30 with CalMAN 5 Enthusiast. I'm using a two point calibration (30 IRE and 80 IRE), and can get the RGB balance within3 dE, but am experiencing a weird overall RGB curve across 0-100 IRE:



Can anyone help me understand why I'm seeing this behavior? I'm using Custom picture mode, Warm 2, 2.2 Gamma, with all the "extra" picture settings disabled.

The gamma curve drops off substantially at 30 IRE:



Is this an issue with my set, or potentially with my meter (i1Display Pro)?

Any help is greatly appreciated.
Hi,

I see you got some great advice and it is well worth following up on. I am going to offer an unorthodox approach. If it does work just reset or redo as you would do normally. In the RGB image I see you have it set at "absolute"; that's okay. It is the image of the Gamma Log is what I am interested in. If you do a grayscale and take note of the "Y" values in comparison to the "Target Y" values you will probably see that the "Y" values are much higher then the "Target Y" values. Here is the clincher, some displays track linear while others do not. Edit the grayscale so you can see both of the aforementioned values on the screen and run a grayscale reading. If I am right, you will notice what I had surmised and the "Y" values will be much higher. Adjust the RGB to be equal, then equally adjust all RGB values to bring the "Y" as close to the "Target Y" value for both the 30% and the 80%. This is time consuming but you will find it worth it. If your display tracks linear you will note the values throughout the grayscale will come in line after doing a re-read. If it isn't linear you will notice that the 30% and the 80% appear perfect while all other points appear chaotic. If all works well (if tracking linear), not only will the Gamma Log correct itself but the RGB should level off as well. You can't hurt your display by doing this.

Last edited by randal_r; 06-27-2014 at 05:47 AM.
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post #8 of 17 Old 06-28-2014, 07:01 PM - Thread Starter
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Thanks to everyone for the suggestions. I finally got the chance to re-calibrate tonight with the following results:







I still can't get the Gamma curve up to 2.2 at the high end. I took the suggestion to lower all RGB balance to try to decrease the brightness at the higher IRE, but these results are with the limiting color bottomed out (Red).

My current key settings (I can include all the detail with the W/B highs and lows if helpful):

Picture Mode - User
Color Temp - Warm2
Gamma - 2.4
Content Type - Graphics
Panel Brightness - Mid

Would this constitute a successful calibration? Any additional suggestions are appreciated.
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post #9 of 17 Old 06-28-2014, 07:30 PM
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Quote:
Originally Posted by drangel1 View Post
Thanks to everyone for the suggestions. I finally got the chance to re-calibrate tonight with the following results:







I still can't get the Gamma curve up to 2.2 at the high end. I took the suggestion to lower all RGB balance to try to decrease the brightness at the higher IRE, but these results are with the limiting color bottomed out (Red).

My current key settings (I can include all the detail with the W/B highs and lows if helpful):

Picture Mode - User
Color Temp - Warm2
Gamma - 2.4
Content Type - Graphics
Panel Brightness - Mid

Would this constitute a successful calibration? Any additional suggestions are appreciated.
Did you do a comparison of the "Y" value to the Target "Y" in the grayscale? The Gamma chart still exhibits very high values.
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post #10 of 17 Old 06-28-2014, 07:45 PM - Thread Starter
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Quote:
Originally Posted by randal_r View Post
Did you do a comparison of the "Y" value to the Target "Y" in the grayscale? The Gamma chart still exhibits very high values.
I did - full results below. I attempted to balance, then reduce, the RGB values to bring down the Target "Y" but as I mentioned the limiting color bottomed out (R). Unfortunately, to keep RGB in balance G and B are considerably higher than R at 80 IRE.

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post #11 of 17 Old 06-28-2014, 08:07 PM
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Don't use "Y fL", use the "Y". Even with the values that you have chosen shows the issues. O% and 100% are always stable and constant. The 100% is the value is set when you adjust the backlight or cell light (THX standard is 35 Ft L). The higher the "Y" over the target value the higher the Gamma and the reverse the lower the Gamma.

A question; is the "warm 2" the closest to D65? Some people choose a setting because they read it somewhere that is was the setting to use. Displays vary and what worked on one display doesn't work on another. Re-test or try "warm 1". I to have experienced this situation and changing the temperature setting helped.

I really don't know how much you know about CalMAN 5 but the datagrid can be edited to reflect the proper "Y" value. Please let me know how it progresses for you. For years I have looked at many reports that have been submitted and in about 97% of them never do they utilize the target values. They are there for a reason. How do you know if your adjustments are correct without a reference target?

Last edited by randal_r; 06-28-2014 at 08:34 PM.
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post #12 of 17 Old 06-28-2014, 08:59 PM
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Quote:
Originally Posted by randal_r View Post
Don't use "Y fL", use the "Y". Even with the values that you have chosen shows the issues. O% and 100% are always stable and constant. The 100% is the value is set when you adjust the backlight or cell light (THX standard is 35 Ft L). The higher the "Y" over the target value the higher the Gamma and the reverse the lower the Gamma.

A question; is the "warm 2" the closest to D65? Some people choose a setting because they read it somewhere that is was the setting to use. Displays vary and what worked on one display doesn't work on another. Re-test or try "warm 1". I to have experienced this situation and changing the temperature setting helped.

I really don't know how much you know about CalMAN 5 but the datagrid can be edited to reflect the proper "Y" value. Please let me know how it progresses for you. For years I have looked at many reports that have been submitted and in about 97% of them never do they utilize the target values. They are there for a reason. How do you know if your adjustments are correct without a reference target?
randal,

'Y' is a measurement of luminance. It requires a unit of measurement -- either foot-Lambert (ftL) or candela per square meter (cd/m^2). 'Y' without an associated unit is meaningless.

Larry
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post #13 of 17 Old 06-28-2014, 10:29 PM
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You are actually closer than you might think. Note that you are only 1 ft/l or so off the luminance (Y) target values from 70 up. This close to 100% White, small differences have a big impact in the gamma plot.

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post #14 of 17 Old 06-29-2014, 07:10 AM
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I ran this through Calman for illustration purposes. The first image is my gamma screen without data the second is the gamma screen with simulated data. Note the differences between the "Target Y" and the "Y". The "Y" values are lower the the target values resulting in a higher Gamma (darker image). If the the "Y" values were greater than the target values then the results would be a lower Gamma (brighter image).

The third and forth images are the grayscale screens (without and with simulated data respectively). note the 60% value and how the RGB appears to be fine. Then note the "Y" & "Target Y" values. even though the graph shows an excellent setting for the x & y values the Y value states other wise. As I had stated in a previous posting not utilizing the numeric target values may only be half the job.

To LarryInRI, you are correct. I have submitted the "Y" variables from the Calman properties section in the last image that show where the values for "Y" appear the same. Thank you for your point of view it was a great help.

To drangel1, the issue with the color's bottoming out; I too have experienced this. Re-evaluating the color temperature is worth giving a try. If the "Warm 2" is the best setting, sometimes we have to settle for how the engineers designed the display. My advice is not to give up.
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Last edited by randal_r; 06-29-2014 at 07:34 AM.
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post #15 of 17 Old 06-29-2014, 09:33 AM - Thread Starter
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Quote:
Originally Posted by randal_r View Post
I ran this through Calman for illustration purposes. The first image is my gamma screen without data the second is the gamma screen with simulated data. Note the differences between the "Target Y" and the "Y". The "Y" values are lower the the target values resulting in a higher Gamma (darker image). If the the "Y" values were greater than the target values then the results would be a lower Gamma (brighter image).

The third and forth images are the grayscale screens (without and with simulated data respectively). note the 60% value and how the RGB appears to be fine. Then note the "Y" & "Target Y" values. even though the graph shows an excellent setting for the x & y values the Y value states other wise. As I had stated in a previous posting not utilizing the numeric target values may only be half the job.

To LarryInRI, you are correct. I have submitted the "Y" variables from the Calman properties section in the last image that show where the values for "Y" appear the same. Thank you for your point of view it was a great help.

To drangel1, the issue with the color's bottoming out; I too have experienced this. Re-evaluating the color temperature is worth giving a try. If the "Warm 2" is the best setting, sometimes we have to settle for how the engineers designed the display. My advice is not to give up.
Thanks randal_r. I'm still getting acclimated to the CalMAN 5 workflows. Is there a specific workflow, whether built-in or custom, that you'd recommend? I don't recall seeing the workflows you're using in the screenshots.
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post #16 of 17 Old 06-29-2014, 07:13 PM
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I have a number of workflows that are not standard issue. Some I have designed myself and others that only those who have taken the video calibration courses will have. As for the one that I used for the illustration, is designed for those starting out or better. That one I give away freely while others I can not.
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post #17 of 17 Old 06-30-2014, 12:35 PM
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you can get to the options by clicking on the data grid and then the right panel arrow.
If you can find some dead space on datagrid then you can also right-click the chart and select properties from context menu.

We have have 5 types of Y in the product. Y, Y_fL, Y_Lux, Y_fc, and Y_unit.

metric and imperial emissive measurements:
Y is in Candelas per meter squared
Y_fL is in Foot Lamberts

metric and imperial reflective measurements:
Y_Lux is Lux
Y_fc is Foot Candles.

Y_unit is the user selectable unit so that it returns one of the previous 4 types based on user preference.

They are all valid, and as long as you are consistent.

Joel Barsotti
SpectraCal
CalMAN Lead Developer
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