So I started fresh on the Bright Cinema picture mode, I used BT2390 from start to finish. I measured 137 nits at 100% white on my first grayscale sweep so I used that as the white level.
Here is the grayscale after adjusting the two point controls at 20% & 80%
After adjusting the 2 point controls I lost about 8 nits so I dont know if I should have changed the white level to 129 nits before adjusting the gamma controls.
After adjusting the gamma controls alone I could not get close to matching the EOTF curve.
So I ended up maxing out the contrast control to get the curve close & then used the gamma controls to bring the low end back into line
I then moved onto the CMS which started off like this.
After adjustments I could only manage this.
So I went back to the grayscale & remeasured & got this.
So I adjusted the gamma controls again to bring things back into line.
Then back to the CMS & without any adjustment error was dramatically reduced.
I had another go at adjusting the CMS.
Then checked the grayscale again
So any good?