@Magokelvin

when rendering with the menu optio create photo with yafaray I obtain a bright result (don't know how to post a photo here)
when using the new 2.1 plug in...all of a sudden it becomes all dark?
where do I make mistake?

This How to share images and files post pinned to the forum gallery will be helpful to you.
Then post a screenshot of the Create photo / YafaRay panel with a finished rendering.
Do the same with the Simple photo rendering (v2.1) panel and the properties panel of the selected rendering engine.

These images may help to better understand your problem.

Enko