I have the Canon TS-E 17mm in my armoury but that’s big, expensive and the front element is very exposed. For these reasons I want something smaller, lighter and decently sharp to use as a carry around ultra-wide.
I have an old Tamron SP 17mm f/3.5 on the Sony A7r, so decided to test it. This shot was part of the testing, taken just round the corner from my workplace. Unfortunately this Tamron not the answer as it can’t live with the Sony 36MP Sensor, unfortunately.
There is corner smearing and CA, but it’s also got curvature of field problems which mean that it’s just about impossible to get a shot that is sharp in the centre and 2/3 of the way to the corners – it’s either or. It can be disconcerting to see an image that’s soft in the centre, sharpens then softens again. It seems possible that there is an adapter issue, but I strongly suspect that something is out of alignment internally as I’ve never seen such a lack of sharpness from a Tamron lens.
Hopefully the rumoured Zeiss FE wide zoom is a cracker otherwise it’s time to look for a Zeiss 18mm, I guess.
As an aside the A7r, it seems to me, also requires more stopping down to achieve the same apparent depth of field. I assume this is something to do with pixel pitch and circles of confusion but all that is beyond me, really. I just know that I need to stop down a bit more.