I'm find this whole OLED-light vs Contrast (and brightness)-thing very confusing. It looks like it does the same in many ways, even though I know it shouldn't/doesn't.
For example, when calibrating the black level with the use of a THX-disc both raising the OLED-light and raising the brightness make more "black boxes" appear.
Is the difference that OLED-light makes everything brighter while raising brightness (black level) just make details in black better? And what is the relationship between contrast and OLED-light? Lower OLED-light needs a higher contrast setting?
This is what I have found out contrary to what others have said.
OLED light does indeed effect brightness/shadow detail.
To test this set an input at default values for ISF Dark. OLED light 80, Brightness 50, Contrast 85 and gamma 2.2 (BT.1886 and 2.4 are too dark for this test I have found).
Display a black image or use the black bars on a movie.
Make sure this is in the evening and turn off all lights off.
Grab a toilet roll or roll up a piece of card. You want a tube that won't damage the screen to place against it.
Close one eye and look through the tube. Block out any light other than that coming from the black area of the screen. Allow your eye to adjust. Look for any glowing or sparkling pixels. Don't see any? Up the brightness a notch to 51.
On my TV I could just about perceive a very very feint glow. No sparkling pixels, but glowing nonetheless. Many have said their sets start to glow at 52. But this is most likely due to them running the OLED light at a more modest 40-50 range. Now try the same procedure at OLED light 45. You will see it does not glow or get sparklies until 52 or maybe 53 depending on your set.
My conclusion is that OLED light has some small effect on shadow detail which can be raised by bringing the brightness up a notch and then adjusting IRE lumenance a little in the advanced white balance settings.
I had wondered why the set came from the factory set at OLED light 80 and brightness 50 and this seems to be why. By setting the OLED light lower you are crushing shadow detail and it becomes a bit harder to compensate using brightness and lumenance settings. At the default 80, gamma 2.2 and raising lumenance a little I find shadow detail to be excellent and really punchy. But it does strain the eyes a little at night.
As always. YMMV