Panasonic - High Panel Luminance DIY calibration guide

skyvalley99

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I recently "calibrated" my 60ZT65 using a Panel Luminance (PL) of High in the Pro 1/2 settings using nothing but some test patterns and my eyes in order to maximise light output and wanted to share the method I used, skip to Method below if you don't want to read the background/reasons for doing so. This method should be valid for any Panasonic plasma where you can change the PL

Disclaimer: I am not claiming that this would replace professional calibration and is very subjective, thus I've more than likely made some basic mistakes, so please correct me where wrong!

Using PL of High has the following caveats:

  1. This does not change the light level at which the panel will ABL, or the amount of light output during 'brighter scenes'. However what it does do is increase the average amount of light output so darker content benefits greatly by doing this.
  2. Slight increase in image retention
  3. Bright objects will leave faint trails in dark scenes
  4. Increased heat output at higher contrast values (and thus power consumption)
Background
I've owned various 2013 Panasonic plasma's over the years (specifically the 42GT60 and a 50VT65) and recently managed to get my hands on a fantastic condition 60ZT65. And although its an amazing display it's light output is definitely lower than I'm used to (especially compared to my 42GT60 which still gets pretty bright), this is more of an issue with newer content which tends to skew to a darker overall presentation.

I don't know if this is just the panel I have, or by design, but I've noticed that the ceiling for light output when using PL of Mid is at a contrast setting of 70. Increasing it past this results in zero extra perceived light output (in both bright and dark scenes where ABL is not being hit). I had it set to 60 which is fine for most content but can be a bit dark for modern content (I'm looking at you 1899!!), and also doesn't give me much head room as the panel ages as its very close to the maximum.

So for awhile I wondered if the panel could be calibrated to use the PL of High to get around this, as this vastly increases the general light output of the display and its contrast setting ceiling is 80 with a greatly increased perceived light output when compared to PL Mid at 70. However most recommended settings (and shared calibrated settings you find online) use the PL Mid setting for good reason as using PL High will result in a loss of shadow/highlight detail and generally a blown out/terrible image.

The issue is that the IRE gamma settings are vastly out of whack which is what results in the PL High being so terrible. So I wondered if this could be achieved without using professional calibration to a reasonable level (as I don't have the money atm for the moment and I wonder if any calibrator would do that), and after trial and error I believe I've achieved that and am now enjoying a display where a contrast setting of 55 is more than enough for my eyes (giving me massive headroom as the panel ages).

Method
What you'll need:
  • Test patterns to calibrate the 10 step IRE greyscale (included in the attached archive are the two I used which are taken taken/adapted from the MP4-2C patterns found here AVS HD 709 - Blu-ray & MP4 Calibration)
    • 10 Step Greyscale pattern (the image is flipped in order to ease in changing between Pro 1/2 settings and not using 100% white on the rest of the screen as I found this gave the best result)
    • 20 Step Greyscale pattern (for further validation)
  • A way of playing these patterns (I used a raspberry pi)
  • ~30/40 mins
  • Good pair of eyes!
Preparation:
Set both the Pro 1/2 presets completely to their defaults on the input you're going to use to play the test patterns (this includes all sub settings including gamma, colour management, and white balance).

Prepare the Pro 1/2 presets as follows (Pro 1 is going to be the reference and Pro 2 is going to be the PL High being calibrated):
  1. Increase the contrast on both Pro 1/2 to 100 (this is to completely account for ABL)
  2. Set PL to High in Pro 2.
  3. Calibrate the brightness value for both Pro settings, see Note 1 if unsure how to do this
  4. Set the gamma values for Pro 1/2. See Note 2on which PL Mid/High gamma value to use.
    1. I targeted PL Mid 2.2 and PL High 2.0 as I was able to hit the required 10 step greyscale values pretty well.
  5. Calibrate out any colour tints, see Note 3
10 Step Calibration:
In a media player load up the 10 step greyscale test pattern and pause it.

This stage is about matching each 10 point greyscale step % between Pro 1/2 in order to make the required adjustments to the associated greyscale IRE adjustment (Its best to start at the 90% greyscale/IRE setting as 100 can be calibrated using the 20 step greyscale once finished)
  1. Switching between Pro 1/2 observe the current greystep % (See Note 4 for tips on this)
  2. If Pro 1 looks darker than Po 2 then decrease the value at that IRE value of Pro 2, if Pro 1 looks lighter than Pro 2 then increase the gain value at that IRE value of Pro 2. If the difference is large then use a delta of +/5, once it gets close then use a delta of +/- 1
  3. Repeat for each IRE value of 10 to 90. (Some values may well approach +/- 50)
  4. When all are calibrated ensure that by changing the IRE setting by +1 for each 10 to 90 in turn results in a visual change, and setting it back to the calibrated value still looks correct. If not then re-calibrate
20 Step Calibration (validation):
In a media player load up the 20 step greyscale test pattern and pause it.

This stage is about setting the 100 IRE value by using the 20 step greyscale test pattern, and further validation of the values set during the 10 step calibration due to combined IRE setting errors being more visual across the 20 steps.
  1. Switch between Pro 1/2 and observe the first 3 grey steps starting at, and including, pure white and adjust until they look the same. This will most likely by in the range of -5 to 0
  2. Switch between Pro 1/2 and validate the two look visually similar, small differences are understandable. If larger differences are noticed then go back to the 10 point and repeat the 10 step calibration for that IRE level (NB the approx IRE value that needs adjusting can be approximated from the 20 point as each two steps in the 20 point are equal to one one in the IRE, its approx as there is some overlap but this should get you into the right area)
Once the results look good set the contrast to a much lower value (I used 60) for Pro 2 and use other content to further dial in the value until you're happy with the results.

The best way to tell if you've done it correctly is from skin tones, if you see any obvious red/green banding in transitions from highlights to darker areas (forehead/nose/neck to 'in shadow' areas) then repeat the process. The most common pitfall is over-shooting or under shooting the value required which is why its important that once you think you've got it dialled in to go through each IRE value and change it and validate this changes greyscale comparison at the associated % greyscale value, this confirms you're sitting at the right value

For reference after doing this I ended up with the following gamma settings:
SettingValue
Gamma2.0
10+50 (This gets close but there is still a difference)
20+17
30+1
40-28
50-36
60-35
70-29
80-23
90-18
100-2

Note 1: The best way to calibrate the brightness (without using a pattern) is to pause on some dark content, or letterboxed material, then sitting close to the screen increase the brightness to the point until you suddenly see an increased dithering in 'black areas' and then decrease it back by one value. For reference on my panel PL Mid is +4 and PL High is +7

Note 2: I noticed from experimentation that in order to hit the required 10 Step greyscale adjustments in PL High you need to compare it against a gamma value of 1 step higher in PL Mid . Below shows what I mean:
PL Mid Gamma (target) PL High Gamma
2.01.8
2.22.0
2.42.2
2.62.4

So If you're wanting to target PL Mid of 2.4 you'll need to use 2.2 in PL High, it should be noted when using PL High of 1.8 in order to target 2.0 I noticed that on my panel you will end up maxing out the mid 10 step greyscale values and will get close but win't be able to hit it 100%.

Note 3: My set really pushes red, and this is exacerbated when using PL of High. I ended up using a R-Gain of -8 in PL Mid and -14 in PL High, you can use the 10 step test pattern to help with this

Note 4: The method that worked well for me was to sit ~2m away, close one eye and focus on the current greystep % being adjusted and alternatively block the step to the left and right of the current one while switching between Pro 1/2. This took a bit of practice to get right, and you have to be careful as the eyes will play tricks on you when doing a first pass and the value to the left/right will influence what you see, which is why several passes are required
 

Attachments

  • Panasonic-PL-High-Calibration.zip
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