Upload & Sell: Off
Thanks for the info Roy. I'm using a Canon 5D2 which rules out Samyang, as they don't make diagonal fisheyes for full frame. I'll be taking a closer look at the Zenitar now.
My mistake; I didn't realise there wasn't an FF version of the Samyang FE. The consensus seems to be that the Sigma 15mm is the best 3rd party lens in this design, although I believe it's almost as expensive as the Canon versions. You can definitely get OK results out of the Zenitar and it's cheap enough to buy and resell without losing too much money. Its weakness, as I mentioned, is that it's soft until stopped right down - particularly, I imagine, on a sensor with so much resolution - I used mine on a 12 mp D700 - and you have to keep it pointed away from bright light sources. I imagine you may well find a used version without difficulty... given that it isn't that great.