It will have black edges on FX, it's a DX only lens.
You can cut off the hood with a saw and get close to a circular fisheye effect. Here is what it looks like on FX with the hood intact: http://photo.net/nikon-camera-forum/00QOzN
You could just get the 16mm fisheye Nikkor that covers all of an FX frame.
well, it works pretty well in DX and in circular mode... I already discussed this in a recent post. Here is a "cut and paste" of the post in question:
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You can also have a lot of fun with a 10.5 on FX if you do a circular crop... this gives a more interesting pespective than a rectilinear fisheye.
See what I did with it here: http://users.skynet.be/van.hooveld/tips/fishond3.htm
