[wim]

Wim, isn't it funny that for the longest time, 12mm of the Sigma 12-24 (or the Voigtländer prime) was the absolute widest one could get without defishing, and then all of a sudden there's a wealth of options all the way down to 9mm.

By the way, Lenstip has reviewed the 9mm recently. Totally not perfect (CA, huge distortion, astigmatism, flare, strong vignetting...) but since it's the only game in town for 9mm, it's acceptable, especially given that they found it to be pretty sharp.

Well, I did my research before jumping to the Samyang 10 mm .

Basically, most 9 to 13 mm lenses are not all that great beyond the centre, and often have lots of CA, astigmatism, flaring and indeed vignetting. There are a few that do better in one or two of the areas, the Canon 11-24 being one of them (at 11 mm I mean), but overall I think it loses too much sharpness beyond the centre of the image.

The Voightlander 12 mm and 10 mm aren't too bad either, but they are not as sharp or as well corrected as the Samyang 10 mm, and they start at F/5.6, which means you really need to stop down to F/11 to get optimal results, as is proven by the reviews I have seen.

With all of these lenses you need to stop down the aperture at least two stops anyway to get a properly sharp image including the corners, and where the Samyang stands out is that it actually is the sharpest in the corners at F/8, has very little CA, barely any coma, and distortion is quite a low, simple barrel distortion at a rather low level compared to any other lens in this class (and because it is simple barrel distortion, easy to correct).

All in all, highly recommendable AFAIAC .

Oh, even on my Olympuses with the 0.71x and 0.64x speedboosters it still is an extreme WA lens . With the 0.64x one it actually becomes wider than any native lens available for MFT, 6.4 mm F/2.24 - not too shabby IOW .

Kind regards, Wim

P.S.: Several months after my research, Christopher Frost did a review too: https://www.youtube.com/watch?v=K8rFZKkP7Cs