First impressions, rather than an in-depth review.
Rather good. In fact really good, or at least my copy is, but to be fair I haven't heard any negative comments about QC.
It's very sharp, but you knew that anyway.
It's a bit big and heavy-ish but feels robust. Build quality appears very good.
Colour rendition is really nice, as is bokeh IMO.
CA is there at f1.4, there's no getting away from it but it seems to go by f1.8/f2 however at f1.4 it is, without doubt, also sharp all the way from corner to corner and any CA can be got rid of post processing. I've never been a fan of lenses that quote a wide aperture that is in fact quite poor from a definition point of view and this one definitely does not fall into that category - it is sharp across the board.
AF is absolutely spot on. No problems there at all. Will test further with Reikan Focal and report back.
All of the above relates to use with the EOS 5DS. I'll attach it to my 1DX soon and will follow-up here.
So far I'm very impressed. Well done Sigma...it's not a cheap lens but nothing this good will ever come cheap.
Attached photo of my Jack Russell may demonstrate DOF or lack of it at F1.4. Bear in mind she never keeps still and focus point is on her nose. No post processing done at all. Just a raw file from camera.
Follow-up 07/08/2017...Reikan Focal AFMA resulted in a setting of -3 which is the real world is four fifths of bugger all along with a focus consistency of 96% so no isssues there when mounted on the 5DS however my
1DX is proving problematic with Focal. It's the body, not the lens so I have raised a ticket with Reikan and will report back as and when.
Follow-up 11/08/2017...Have finally managed to get FoCal to work with the 1DX. Involves a workaround and Reikan are on the case. Results are excellent, sharpness as expected ie pretty darn good, consistency of focus 99.6% which is really good and that's after 3 runs. Surprisingly,or not maybe, my Canon 100mm f2.8L macro IS comes out slightly better in the sharpness results on the 1DX although I have found historically that FoCal can be a bit quirky. Bearing in mind that currently the Canon 100mm f2.8L IS can be had for around £650 and the Sigma 85mm f1.4 Art at £785 so the difference in price of £135 means you get a lens that lets in twice as much light and is sharp across the board at f1.4 although CA is evident but not excessive.
I think that's a good deal, and yes that's grey import prices. Others, who have the money to spare may disagree.