Hi Steve,
Regarding HDR 3D LUT calibration, I have a question:
During calibration measurements, a fixed aspect ratio pattern is used, such as a 5% window size, for calibration. However, most displays have an APL mechanism, where the larger the window aspect ratio, the lower the peak brightness. Can a 3D LUT calibrated using a 5% window still accurately function with other aspect ratio patterns?
My point is, during video playback, the peak brightness of different scenes varies, and the peak brightness of different scenes is not the same. Can a 3D LUT calibrated using a fixed-ratio pattern accurately calibrate all scenarios?
Is it necessary to measure the APL mechanism separately and then combine it with the 3D LUT to form a 4D LUT? Of course, this might just be my overthinking.
Thank you for your clarification.

No - any calibration with a display that has APL type operation will only be accurate with the effective APL value active when profiling.
Basically, any APL type function will defeat any calibration - LUT based, or otherwise.

Steve

Steve
Thank you for your response.
In fact, almost all HDR displays currently have APL issues. Is there no perfect and accurate HDR calibration solution?
I imagine a 4D LUT with a 5% step pattern ratio, from 0-100%, performing a complete 3D LUT, forming a 4D LUT, with other ratios generated through interpolation.
Or are there other solutions? Does Colourspace have any plans?

As said, any APL type function will defeat any calibration - LUT based, or otherwise.

Steve

Is this the same as local dimming?
How much window calibration is correct for this situation?
Or should I just use Globle dimming?

Local dimming is usually associated with FALD displays.
If you use the Search function, for both Topic Titles, and Message, you will see various discussions on this.

Steve