Alfa channel isn't completely transparent

[Cheesemsmsm]

Uncheck "Visible in masks" in the glass material.

[maru]

Thanks Maru but this the solution you suggested is problematic - it disables all the hdr reflection from the scene materials.

Well, what would you like it to be? You can't easily replace reflections anyway, e.g. on non-flat surfaces. You can put whatever you like in the reflections override slot.

[Dollmaker]

Can someone tell me how to take care of this halo issue for objects behind glass where BG is replaced in PS? Thanks :)

[maru]

Rendering with direct visibility override for enviro set to black should work here. See (in this thread): https://forum.corona-renderer.com/index.php?topic=17065.msg107040#msg107040