Well I am trying to learn how to place CG objects into real photos and make it believeable. This is my first try at this type of thing so I decided to start as simple as possible... a sphere! :)  So I downloaded this pic off of google.....

I wanted to add the sphere to the closest table. So using the pic as a background image, and looking through the cam, I added a plane for the table (to catch shadows), the sphere on the plane, and 2 area lights from the windows. Also added a small back light for ambience.

I set OSA to 11, area lights to 11x9 samples, and raytracing on. And got this......

It's looking pretty good, but I want it better. Can you guys help me out? Tell me what you see when you look at this image that keeps you from believeing the sphere is really there. Any crits are welcomed please, no experience required :) I would like to learn all the in's and out's of this before I do a more complex project.