Meter profiling: does changing gamma preset invalidate the profile? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Unread 03-02-2017, 01:40 AM - Thread Starter
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Meter profiling: does changing gamma preset invalidate the profile?

I took reasonable care in matching the FOV between the i1 pro 2 (spectro) and the i1 display pro 3 (colorimeter).

I then took WRGBCMY readings and the profiled meter agreed with the spectro. So I started calibrating, with as only major change after making the profile a different gamma pre-set on the VT60 (2.4 instead of 2.2). I finished calibrating and decided to take new WRGBCMY readings with both spectro and colorimeter. Profile was miles off. I mean differences of 0.01 x,y.

Is it the gamma pre-set or do I have to time everything to allow a certain warm up time for all components? The dE numbers in the screenshot are just the delta between spectro and colorimeter. They do not represent the error compared to the reference.

Also, one thing I notice is that the profiled meter always seems to be off a bit more for red and green. See screenshot
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My gear: Panasonic TH-42PF11EK pro plasma display + TX-P55VT60E -- Iscan Duo video processor -- i1 display 3 colorimeter -- i1 pro 2 spectrometer

Last edited by Jeroen1000; 03-02-2017 at 01:49 AM.
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post #2 of 7 Unread 03-02-2017, 03:06 AM
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Originally Posted by Jeroen1000 View Post
I took reasonable care in matching the FOV between the i1 pro 2 (spectro) and the i1 display pro 3 (colorimeter).

I then took WRGBCMY readings and the profiled meter agreed with the spectro. So I started calibrating, with as only major change after making the profile a different gamma pre-set on the VT60 (2.4 instead of 2.2). I finished calibrating and decided to take new WRGBCMY readings with both spectro and colorimeter. Profile was miles off. I mean differences of 0.01 x,y.

Is it the gamma pre-set or do I have to time everything to allow a certain warm up time for all components? The dE numbers in the screenshot are just the delta between spectro and colorimeter. They do not represent the error compared to the reference.

Also, one thing I notice is that the profiled meter always seems to be off a bit more for red and green. See screenshot
Hi, what software are you using? ... in CalMAN, it has a meter profiling issue which is floating for years, see here: CalMan 5 Release Notes and Discussion

You need multiple verification runs with CalMAN until to get a valid meter correction table, this is why I have design specific meter profiling check layout page.

A lot of users very familiar with the meter profiling procedure are surprised when they perform this test for their first time and found that their created meter correction table is not so accurate...but they haven't realized that can be possible because they were always following the correct procedure but they were missing to check the accuracy of the created meter profile.

Sometimes you will need to re-perform your meter profiling a second time to get a better verification results, with tighter tolerances.

NIST's accepted tolerances are below xy +-0.001 and +-1.5% Luminance.

If you are using CalMAN you can design a workflow layout page like the picture below, of use the Meter Profiling Check Layout Page can be found inside the CalMAN Workflows I send to my calibration disk users.....and it's very useful for users to check if their meter profiling correction table is accurate.



There a lot of times where users are skipping that step and loose a lot of hours later until to realize that the their final result is not so good and they have to re-calibrated from the start because the meter profiling was not good.

About meters warm-up time, just leave their USB plug connected with your notebook for some time before starting measurements. The recommended warm up time is about 20-30 min. The exact time depends from the temperature conditions. It can be longer if the device came from out side in winter time and will be shorter if stored at room temperature.

The meter must be at room temperature, when the meter has stable temperature you will have stable readings over the time, heat is not good for the sensors, when the meter is becoming warm, more noise is added to the sensor. (reducing S/N ratio).

Also, EBU TECH.3325 Publication (Methods for the Measurement of the performance of Studio Monitors) recommends the distance measuring geometry rather than the contact method.
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post #3 of 7 Unread 03-02-2017, 03:19 AM - Thread Starter
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Hi Ted,

Just found the thread your referenced to and put a comment there. It is Calman and yes green y and red x have the issue. I'm going to e-mail their support as this is really bugging me
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Ted,

How it can check the meter calibration when the display may not be accurate?

- Rich

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Ted,

How it can check the meter calibration when the display may not be accurate?

- Rich
Hi Rich, what do you mean?

You perform a meter correction table procedure before starting the calibration, so the display is un-calibrated (inaccurate).

You need a spectro and a colorimeter, so you apply to the colorimeter an offset (3x3 XYZ matrix table) to improve your colorimeter color accurancy from using your spectro as a reference, so you start your calibration only using your colorimeter after that; which is faster and better to low light measurements and don't require periodically dark readings like consumer spectro's.

To check after you have applied the meter correction table to your colorimeter to see if the table is valid; you have to check your colorimeter with the offset that it reads like your spectro, this is why you need to verify the agreement between the 2 meter readings.
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post #6 of 7 Unread Today, 03:49 PM
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Quote:
Originally Posted by ConnecTEDDD View Post
Hi Rich, what do you mean?

You perform a meter correction table procedure before starting the calibration, so the display is un-calibrated (inaccurate).

You need a spectro and a colorimeter, so you apply to the colorimeter an offset (3x3 XYZ matrix table) to improve your colorimeter color accurancy from using your spectro as a reference, so you start your calibration only using your colorimeter after that; which is faster and better to low light measurements and don't require periodically dark readings like consumer spectro's.

To check after you have applied the meter correction table to your colorimeter to see if the table is valid; you have to check your colorimeter with the offset that it reads like your spectro, this is why you need to verify the agreement between the 2 meter readings.
OK, so using your test pattern the readings should be the same after correction.. I'll try that tonight.

Thanks,

- Rich

Oppo UPD-203 | Sonica DAC | BDP-105D | HA-1 | PM-1 | Emotiva XMC-1 | ATI Signature AT6002 x 2 + AT6006 | Revel Salon2s, Voice2, Studio2s | Velodyne HGS-15 | LG B6 | Lumagen 2020
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post #7 of 7 Unread Today, 03:53 PM
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OK, so using your test pattern the readings should be the same after correction.. I'll try that tonight.

Thanks,

- Rich
Yes, the measurements between spectro-profiled colorimeter have to agree with max xy +-0.001 and +-1.5% Y difference.

Ted's LightSpace CMS Calibration Disk Free Version for Free Calibration Software: LightSpace DPS / CalMAN ColorChecker / HCFR
S/W: LightSpace CMS, SpaceMan ICC, SpaceMatch DCM, CalMAN 5, CalMAN RGB, ChromaPure, ControlCAL
V/P: eeColor 3D LUT Box - P/G: DVDO AVLab TPG
Meters: JETI Specbos 1211, Klein K-10A, i1PRO2, i1PRO, SpectraCAL C6, i1D3, C5
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