I'm working on a project where I need it really wide: 15-17 mm are giving the best perspective for what I want. Since this runs for some time now I would like to share some experiences and perhaps there is some input form someone else too. It is not about the question what is the sharpest, highest resolution lens. I have to work handheld anyway. I'm quite happy with my images so far. I'm photographing for a long time now (35mm, Hasselblad V, Sinar now Canon full frame since it is out) but have never worked with such wide angles.
I use the following workflow:
- Canon 5D MarkII, handheld (is a must), AF, Sigma 12-24, Sigma 14/2.8 and the Canon 14/2.8L, ISO 800-3200, f8
- Lightroom 2 as far as possible -> Photoshop with PT lens plugin (for distortion and perspective correction, would be a dream to have that included into Lightroom).
So now my experience:
Focusing is more critical than I thought. My subject is in the range between 1-10m. You can't only set distance even with f8 and depth of field will do the trick.
Canon 14/2.8L and Sigma 14/2.8 look like the same lens in different barrels: both sharper than Sigma 12-24 if focused correctly, but unreliable auto focus and sharpness is sometimes only in one or the other corner, can't reproduce focusing. I found out that the image jumps around during focusing between 1m and infinity it looks like the lens element that is moved for focusing just wobbles around if you go from 1 m to infinity (Canon and Sigma behave almost identical), I see this during if I'm using live view on my 5D Mark II. If you correct distortion (which is way more than with the Sigma 12-24@15) in PTLens you loose some wide angle and you get more like a 15mm field of view.
Sigma 12-24@15: not as sharp as the fixed focal lengths, almost no distorsion and chromatic abberation, no jumping around image during focusing between 1m and infinity, reliable auto focus and sharpness in all corners. Mechanical better but not as sharp as the fixed focal lengths, IF THEY FOCUS CORRECTLY.
Similar experience with wide angle optics?
Remark: Sure I should use the Nikon 14-24/2.8 with an adapter and wait for the TS-E 17 mm. But you can't always get what you want.