after some first problems I got the translucency effect of curtains working. Quite nice looking.
Also I tried to get an effect for an exterior scene, but there I had no luck. Attached some comparison images.
First I have overseen that a leaf effect is added, because it was very light only - see three image comparison. I like the translucency effect per 500% sun, but only the sun light is to bright.
Later, from an other view angle and skybox disabled I got other effects, the leaf effect cause an additional darkening. (auto exposure and contrast disabled).