Hi,
I use a JVC X3 in wide2 mode, with Lumagen running a lightspace LUT to fit chroma for rec709 nicely.

I am looking in to a separate LUT to correct for UHD Blu-ray (have a panasonic UB500, which may be able to strip HDR) and Fire TV 4K.

I have and HD fury that downscales to 1080p before the Lumagen. I want to retain WCG within P3. Happy to lose 4K and HDR.

Any suggestions for building

To be honest, I'm not sure what you are asking?
You just need to make a calibration LUT as normal, targeted at UHD.

But, I'll get Gordon Fraser from Convergent AV - UK Lumagen supplier - to comment too.

Steve

You cannot really LOSE HDR. You are just choossing where to do the HDR to SDR tonemapping. Either in the player or in the Lumagen processor. Which you choose really depends on the lumagen you own. If you have a Radiance Pro then follow my guide which is available to download from front page of rthe convergent-av.co.uk website

If you have an older Radiance then you probably want to use something like an HD FURY Integrale to force the players to output SDR REC2020 and then you'd create a LUT in Lightspace to map your display to UHD/REC2020 with your preferred gamma. Then i'd compare that to letting the player output SDR/REC709 for UHD SDR content with a lUT targetting REC709. You may find that if you have something with a 5x5x5 lut you may not get good results for REC2020...i haven't tried so can't be sure.

Thanks Gents. I understand the gamma is very different. Its not a Lumagen Pro, but i am downscaling in the HDfury to 1080 as 4K resolution is not important to me here.

Sorry, can you define in more detail exactly what you are trying to achieve?

Steve

Playback of UHD blu-ray through a JVC X3 projector preserving WCG to a high % of DCI-P3, using a LUT in a lumagen to do gamma mapping from HDR or SDR.

Ok, that means just calibrating as normal, making a LUT to convert from ST2084 HDR EOTF to 2.4 gamma SDR.
But, the Lumagen will unlikely work as the LUT size is too small, as Gordon commented.

Steve