Display brightness only 270 instead of 400 nits - Probook x360 435 G7

[martin_z_p]

Hi... 

My HP Probook x360 435 G7 - 1Q2W3ES#ABD Display, specified at 400nits only delivers around 270cd/m² at full brightness. I got suspicious because my second display which is rated at 350nits, is much brighter.  Measured: 358nits (cd/m²)... So my Color Spyder is working fine. 

Color accuracy  at 72% NTSC (~100% sRGB) is fine. 
Datasheet shows that all 72% NTSC screens should have 400nits brightness.

Al power savings modes are off.
AMD Vari Bright turned off. 

 
Is there a hidden setting somewhere I´m missing?
Is my screen faulty or maybe the specs cheating?

 I really need to clarify this. 

Thanks. 

[martin_z_p]

Edited:

IMPORTANT note: VESA Display HDR Test does only show standard 270nits for almost every display!
It is not a verified method to check the nits value.


But my colorimeter does correct values:

[tiwookie]

I don't know if my comment really helps, but had a similar issue, which kind of was related to powersaving. It was always dimmed. I tried to configure it via Windows, but this didn't help. After some research and deepdive I found out there's also a switch in the gfx driver. So if you open the Radeon software, there should also be an option for the brightness. This was the issue in my example - maybe it's worth a look for you.