II shoot full frame and right now the widest that I can get is 17mm. I'd like to go wider for some extreme perspective closeup images. I'm debating between the Canon 15 fish and the Canon 14L. The both have similar minimum focusing distance. I certainly like the price of the 15.
There is some wider angle glass from sigma that I was considering but those as well as the wider angle glass from canon gets mixed reviews so I decided to hold off for the time being. If you get something that works, let me know. I think I'd like to go down to around 12mm. Check out sigma and/or tamron then make some very good glass.
For full frame and getting to 12, the Sigma 12-24 is about the only option. The problem is that it's optimized for crop bodies and is really soft around the edges.
It also looks like the Nikon 14-24G and an adapter is a pretty solid combination but I don't think that I want to go that route. I think that I've talked myself into the 15 fisheye. If I need to, I can remove the "fish" with DxO after the capture.
I've used the Sigma 12-14 on my old D300 body and really enjoyed it. It matches the sensor format of that camera and the edge softness has not been objectionable. I think it's more than offset by the creative avenues it opens up. This lens is just plain fun. Also makes a great interior lens when you want to cover a whole room while standing in the corner.
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