Shadow Pass Problem

[user_deleted]

I am rendering a sphere with shadow on it in maya.
when using usebackground shader the catch shedow on the sphere
and comping it with over node , the shadow dont cover all the sphere.
I am using premulti images, but it looks like maybe
the shadow pass dosn't premulti.
what is a way to render and comp shadows on objects
and still make the shadow cover all the object?
is it a premulti issue?

[user_deleted]

After some tests I found that if I render the shadow pass as white lambert
and comp it with the min layer node it works realy well,
Has anyone found this process better then use background shadow pass?