The "Wall" image didn't use a tripod. The "Target" images used a tripod and 2-second delay. They all obviously used the (tiny) built-in a lenshood. No filters were used.
The target wasn't big enough to include the corners, so a proper comparison between the centre, the edges, and the corners, isn't possible with these images. But the nature of the lens makes such a comparison pretty meaningless anyway.
I used aperture priority and autofocus throughout.
|1.4 (Kenko)||14 (10 on lens)||f/4.9 (f/3.5 on camera)||f/11 (f/8 on camera)|
|1.4 (Kenko)||17 (12 on lens)||f/5.6 (f/4 on camera)||f/11 (f/8 on camera)|
|1.4 (Kenko)||20 (14 on lens)||f/5.6 (f/4 on camera)||f/11 (f/8 on camera)|
|1.4 (Kenko)||24 (17 on lens)||f/6.3 (f/4.5 on camera) (out-of-focus)||f/11 (f/8 on camera)|
I bought this for fun, but it has exceeded my expectations. A fish-eye lens probably isn't important enough to me to buy another, but I would be happy if I could use it, even with limitations, on a Pentax FF camera.
As far as I can tell, I could use this lens satisfactorily for its fish-eye effects at 14mm and 17mm. On an APS-C sensor the fish-eye effect is not strong at 17mm, but on an FF sensor it is more pronounced.
The lens is so strongly vignetted at 10mm and 12mm that I doubt whether I could get any extra value from it there. (But see below). Unless I were to use it with a teleconverter! Even at the widest angle most of the vignetting has gone. I can't judge from my tests what the edge and corner quality is with a teleconverter, but I am sceptical about the possibility that a fish-eye lens can sensibly be used with a teleconverter!
A reply to my Pentax Forums post about these tests pointed out that "... the only problem is the hood", and supplied a link to the following description of (dramatic!) removal of the hood to eliminate the vignetting of the Tokina equivalent of this lens: