but will there be an difference in distortion using the bayonet rather than screw on mount? screw on seems like it will be further from the lense making more distortion, while the bayonet will be closer and minimizing the distortion?

The same lens with two different mounts still has to have its elements at the same position relative to the camera lens.

So if you mean optical distortion, there will be no difference. If you mean mechanical distortion, probably so slight as to be negligible.

The bayonet also attaches/detaches much quicker.

also, is there any difference between a "vx2000" century fisheye and a "vx2100" fisheye? i noticed the different focal lengths and such. does this apply between the cameras?

The Sony add-on lenses have about 2 to 3 times as many threads to unwind on my VX2100, as I have had with other cameras. This can be annoying, when speed is essential, even though it makes it a more secure and durable attachment. I would prefer them to have bayonet mounts for speed, but then, I couldn't use them on other cameras.

Distortion? You mustn't be worried about distortion when you're fitting a fisheye to your VX2.1k. Distortion is what you're buying.

If you're working fast 'n' furious the bayonet is the way to go, though I should warn you that Century's bayonet is much more akin to a breech-lock bayonet than a conventional on-turn-lock type bayonet. Screw threads are a pain in that you have to be so careful not to cross thread them as plastic doesn't take kindly to this treatment.

The downside - as has been mentioned - is that the Sony bayonet limits your use of this lens to a very small number of camcorders. If you go the thread route you can use the fisheye on an HC3 up to a Z1, simply by using thread adapters.

tom.

can i use a bayonet mount century fisheye thats for a vx2000 for my vx2100??

Yes, you certainly can. The bayonet lugs on the VX2000, 2100, PD150 and 170 are all the same.