Photographer Christopher Frost published another interesting review of an older zoom lens which is still very much unique in it’s class – the Sigma 12-24mm F4.5-5.6 II DG HSM – one of the widest full frame zoom lenses that you can find on the market today.
Until the more recent Canon 11-24mm f/4 was introduced, Sigma’s 12-24mm F4.5-5.6 II DG HSM was probably the widest full frame zoom lens in the world and if you are using a Nikon or don’t have $2900 it is still your best option if you want to go crazy wide on a full frame camera.
Although this isn’t an ART lens (it came out before those existed) it still performs fairly well on a full frame camera (you would probably want a dedicated ultra wide APS-C lens if you use an APS-C body, although if you are using both APS-C and FF it can actually give you ultra wide angle on both – which is quite interesting).
From Frost’s test you can see that on FF it is sharp in the center wide open and somewhat less so in the corners with some color fringing at the edges. If you close down sharpness improves in the corners and the darkening in the corners also somewhat disappear.
It has some barrel distortion at 12mm but it isn’t that bad (and probably mostly fixable in post if you are O.K. loosing a bit of the frame from the sides. Again, the IQ on APS-C isn’t as good (especially on the corners but this isn’t a surprise and there are cheaper options).
The Sigma 12-24mm F4.5-5.6 II DG HSM is a special lens and not exactly inexpensive at $950, but compared to the the Canon which cost almost 3 times as much you can think about it as a real bargain.