Daylight Medium Affects Alpha ?

[andrefry]

I made a scene with a mountain object and after rendering and editing in Photoshop, I noticed that my alpha was semi-transparent ? I tried using Layer ID and Layer Mask ID but they also came out with the same semi-transparency.
Eventually I found that clearing my Medium in Daylight tag and putting Thickness to default 1 solved the problem.
So, is it to be expected that using Medium in Daylight tag will make objects in the scene semi-transparent ? Is it a bug or to be expected & if so, is there a workaround ?
I can post up a scene file if that helps ?
Cheers.