Just added my basic sphere with a nice glossy finish. With one lamp (sunlight with black-body input), the scene is dark. So I used the same image as background environment texture, plus some low emitter strength.
The ball is throwing a shadow and emits a red glow on the floor also. I think this can be problematic, we will see …
My solution was not the use the mask on ID thing. But just render the ball with an alpha channel. And use the alpha channel as the MIX factor.
This leaves me to the question. Is MASK by ID aliased (smooth) or not?
The floor also reflect on the red sphere, but the floor is just a grey plain without photo texturing. Would be nice to fix that also.