The staging makes a huge difference too. Notice all the mirrors under the trees and trees sitting in cubbyholes instead of out in the open. Also, all of the glass trees shown are lighter in color so the light shines through better. As well, the set itself is significantly lighter in color, from the flooring to the walls to the curtains and the furniture (with the exception of the piano way in the back).
Edit to add that they have added extra background lighting that stays on when the studio lights are turned down. You can see it on the walls in particular.