Alpha in areas above 1

[RALPH_PINEL]

What is the best way to handle alpha's and antialiasing in areas where the background goes above 1 luminance.
I always get an aliasing issue? In this shot the curtain in the middle of the room is a good example.
Any suggestion would be great.
Cheers.

[Dariusz Makowski (Dadal)]

Render it black using Unpremultiplied EXR. Then post in the whites, glare and so on.

[RALPH_PINEL]

I will give it a try.
Cheers