(Please excuse any unintentional etiquette errors: I posted this in another topic link and I shall remove that one.)
I bought a Sigma 50 Art. I am not at all happy with the focus: it is gorgeously, excruciatingly sharp ... about 1/3 of the time. My standards for "sharp" are pretty high, and my reference lenses are the new 70-200 and 24-70. I am a thoroughly experienced photographer with decades of work behind me.
I am utterly baffled; I never, ever have this problem with other lenses; I have never, for instance, used microfocus adjustment on my 5D3 or 1Dx for my reference lenses. Here are a couple of photos from the other day, and I was focusing on the inner corner of the left eye (the 'medial canthus.') By the way, re. the girl with horns, do not adjust your set, you are not hallucinating: the dots on the cornea are contact lenses ... I will leave these up for a few days. Your thoughts deeply appreciated.https://www.flickr.com/photos/johnrudoff/sets/72157648392663316/