Originally Posted by shoman94
Local dimming on medium vs high will give brighter specular brightness in smaller windows under 10% and the difference at 10% is very minimal..... Maybe 50 nits. So the reason I say medium is because that setting along with XDR on high will yield the best results for peak brightness and following the PQ curve
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Ohhh I think this is starting to click. As explained to me previously (special thanks to JoelArt), XDR works differently in SDR vs. HDR.
In SDR, it tries to expand the ~100 nit information into some of the TV's available brightness capabilities to make things pop more. (I ended up finding out that, for me, this lead to some unpleasant color distortions in SDR, especially with games and certain menus - it seemed to especially throw "off" reds and yellows for me; I was instantly happier once I turned XDR off for SDR, but your mileage may vary). So for the most accurate SDR, XDR need to be off during calibration.
On the flipside, in HDR, XDR is *necessary* to use the entire TV's brightness capabilities fully and map everything properly, and it won't throw off colors the way it can in some situations for SDR. This is to the point that if you turn XDR off, you're actually significantly hampering what HDR can do.
Annnd finally, XDR can ONLY work with Local Dimming On at some level.
So, thinking of it like that, it actually makes sense Local Dimming needs to be on for the HDR assessment; it's the only way the necessary XDR setting can be on.