Top of the Rock is a 3-tiered observation deck on the 67th, 69th, and 70th floors of Rockefeller Centre (the upper decks 260 m above the street level you get an unobstructed, 360 degree view of New York City). Enter on 50th Street between 5th and 6th Avenue.
Once up to the viewing decks, the first two levels have a low wall with large Glass screens which enable you to get great views and photographs, there are reasonable sized gaps between the screens to enable cameras to get clear shots.
The top viewing deck has no screens, just the wall and a fantastic view of Manhattan .