In the second picture on post 5402 of this thread:

On my Eizo CG211, the contrast seems totally different depending on the (portrait or Landscape) orientation of the screen.

In landscape the breast is clearly visible, and hardly visible in portrait... and when I rotate the screen it takes a second or so to change.

Is this due to some sensor reacting to room light, and the screening round the screen letting the light fall or not fall on the sensor?

I have tried ho;ding up a card to provide extra screening... I use a "proper" 5000K luminary.