Help or Advice on 4k 709 Calibration via Decklink

Using Calman or DisplayCal to create a 3D LUT, I get a lower contrast image on my monitor than on an output file.

Here's my hardware setup:

Physical Output is from a Decklink mini 4k via SDI to a Shogun Inferno that acts as a LUT box. From the Inferno the signal goes via HDMI to an LG 31MU97-B 4k monitor. The Shogun has no LUT loaded. The LG is set at custom color to pre-adjust for balanced RGB at 120 nits and 6500 Kelvin.

The Decklink is set to output 4096x2160 DCI RGB 4:4:4:4 though the same results happen if it's set to Y:Cb:Cr 4:2:2

Resolve is set at Rec 709 4096x1716 timelines, 10bit color, full levels, with no LUTs applied. Color space seems not to matter for the patches whether it's ACES, or DaVinci.

Both Calman and DisplayCal are set to generate 3D cube LUTs Rec 709 BT.1886 using Resolve's patches. The resulting LUT is loaded into the Shogun but looks the same if the Shogun is bypassed and the LUT is loaded into the 3D monitor LUT slot in setup. Both the Calman and DisplayCal LUTs look identical on the LG. The image is significantly lower contrast than an output file when that file is played in VLC on a Dell P2715Q that is eye matched to the LG before any LUT is applied.

I've taken the Shogun out of the equation by doing the following: the pre-LUT-d and LUT-ed images were fed to a different HDMI input on the LG from the Decklink HDMI output and compared to the SDI/HDMI path via the Shogun. The two paths' images looked identical.

Does anyone have an idea what may be going on, or additional things to try?

When you import the file back into Resolve, does it match what you've been seeing?

When you import the file back into Resolve, does it match what you've been seeing?

Hi Kays, sorry for the delay in responding but I wanted to dig deeper into DisplayCal's settings (which are very deep) because I thought that may have been my problem, (and I was right).

When the output file was imported back in Resolve it did not match at all the image in VLC. Admittedly the VLC image is on a different monitor but that monitor has been eyematched to the LG and it's the gamma that was way off.

However now that I've adjusted some of DispCal's more hidden settings I'm much, much, closer. I only wish it's documentation was a bit less obscure. The default Resolve settings give ok results but they're just ok. I wish someone here would post best settings for Rec709 and P3 DCI

Here' what I discovered:

When calibrating the LG to Rec 709 BT.1886 in both DisplayCal and Calman the resulting gamma at 50% grey is 2.2, not 2.4. This is the reason for the low contrast image compared to the image on the sRGB Dell. DisplayCal has a Profiling setting called Relative that instead of BT.1886 absolute the gamma curve is adjusted based on the measured black level. That setting provides a &09 calibration that approximately matches the gamma of the Dell.