Unity Bypass, LUT Uploads and LUT Generation Size - new information added

A recent thread here on the LG G5 ( https://lightillusion.com/forums/display-calibration-8/lg-g5-confused-about-hdr-3d-lut-calibration-1585.html ) raised good questions about what actually happens inside the hardware when a LUT is uploaded, and what a Unity Bypass upload resets.

That made us realise this information wasn't documented clearly enough, so we went through every LUT-capable hardware integration in ColourSpace in detail, and have added more specific information to each hardware page of the website ( https://lightillusion.com/guides_hardware.html ).

In general terms:

A Unity Bypass upload has no source LUT. It uses the hardware's own commands to return the selected LUT, or LUTs, to null. On some hardware other settings are also reset to provide a valid calibration starting point, such as disabling internal gamut matrices, which provide no benefit with 3D LUT calibration and can compromise accuracy.
A real LUT upload always starts from the ColourSpace 3D LUT.
Depending on the Load option, and the hardware's internal structure, the 3D LUT may be uploaded as-is, or split into 1D and 3D components. When ColourSpace performs the split, the LUT order within the hardware is accounted for automatically.
Hardware without a combined 1D & 3D Load option is not necessarily a single 3D LUT. Some hardware always receives a 1D & 3D split.

We have also updated the LUT Generation Size page (https://lightillusion.com/lut_size.html).
It now explains why a large LUT Generation Size improves accuracy for all hardware, whatever the hardware LUT size or structure, and especially where a 1D is extracted from the 3D LUT.

Thanks to everyone who asked the questions that led to this.
If anything is still unclear for your specific hardware, please ask here.

Steve

For LG TV's: there is the "Default Unity" LUT, which is available in Colourspace, and the "Unity Bypass" LUT, which is availabe only in the hardware menu drop-down list. When having a view, the both LUT's seem to be identical. Is this really the case,or must one always load the "Unity Bypass" LUT into an LG TV?

Please read the User Guide for LG TVs.
All is explained there

Steve

I actually also still had questions on this topic. I read over the LG TV page a bunch of times, so any remaining misunderstaning is likely an issue on my part. However, I'm still not entirely sure of the difference between "Default Unity" upload, and "Unity Bypass." Below is what I am guessing it means:

Default Unity: Uploads a Unity LUT and resets the Matrix/ De /re-gamma stuff to Unity

Unity Bypass: Bypasses all LUTs, clears any existing LUTs that are stuck on the TV, and also resets the Matrix / De/Re-gamma stuff to Unity.

So to me, it seems like you can either do "Default Unity" or "Unity Bypass" on the TV, whichever you choose.

Is this correct? I'm assuming I misunderstood the documentation.

The LG TV page does say:

"With LG TVs, when Unity Bypass or real LUT data is Uploaded selecting the 3D LUT slot will also reset the 3x3 Matrix and associated 1D de-gamma/re-gamma LUTs to unity, while uploading a 1D LUT will only affect the 1D LUT."

So ANY upload into the 3D LUT slot does the same thing.

Steve

Thanks Steve. Okay great, so my understanding appears to have been correct. You can either just upload Default Unity, or you can do Unity Bypass. Dealer's choice.

Thanks for adding all this extra info.