[nappy]

I tried alpha channels and saved as tif/png..i could not get out the black background.

What I want to do is photoshop a sky in.

[JorisMX]

Turn off any background matte / plane / backdrop or anything that could be in way of your cam looking into infinity. Then Render with alpha channel checked as only output. There are maxwell actions for photoshop available for download here somewhere.

Also, next time use the search function, there are several posts like these on the forum.