I compared a simplified variant of my wall lamps by the sofa with my original design.
I started with shutting down every other light-source, including the outside environment .
I found that I also had to shut off the LightPortal since it gave a fake ambient-like contribution to the light
even when environment was at strength 0. (?!)
When only relying on emission here I found that the object was to small to provide enough
light. Trying to compensate with strength gave a way to hot glare on the lamp.
This is with a moderate strength of 5, emission only.
The Lamp itself used to have a mix of Translucent and emission, here the translucent is turned off to get the Emission only result, (The mixer with a red line is muted)
So, here we are back to my original design. Two spotlights pointing up and down behind the lamp. The role of the Translucent is to let the lamp be brighter where the lightsource behind it is, in this case the spot-lights.
The rendering was 33 and 34 seconds. I think this is a case where the result is worth 2-3% rendering diff… 
… oh… and of course I found that I had messed the model up. Now it’ looks like I intended.
