Pardon my ignorance... I'm still kind of new to the DSLR world. Is this a must have lens for a "newbie"? Do I have to be good with shooting in manual mode? I'm still learning manual and do most of my "shooting" in auto, scene, aperture priority, or shutter priority modes.
I currently own a D5100 and the 18-200mm along with the 35mm.
Thanks for your help
Not sure if you're serious, but here goes:
Extreme-wide angle fisheye lenses like this are just about as "specialised" as it gets, outside of perhaps the tilt-shift stuff. So no, it is not a "must have" unless it fits your shooting style. Fisheye lenses can be fun, but a lot of people get tired of theirs really quickly.