While I love the timeless rendition of my 50 Classic, the somewhat random autofocus was getting a bit tiring. I've seen posts on the net saying that someone sent their Classic in to Sigma service and it came back focusing perfectly.
So last week I packaged up my Classic and sent it off to Ronkonkona (wasn't he a famous disk jockey?) for a tune up before the 4 year warranty runs out in a few months.
Round trip from Portland took 8 days. Very impressive service by Sigma. The technician included a very short note to the affect that he "adjusted AF data sam" Not sure what a sam is, but it's nice to know it's been adjusted.
I eagerly got out my big testing chart and did some autofocus testing in open shade outdoors. I used one shot autofocus.
Sadly, the autofocus is still somewhat random, definitely no better than before. I tested at various distances (6-10 feet) and apertures, usually taking two or three shots and noting how much front or back focus. then went back and tried to duplicate the results. Sometimes I tried pressing the AF button multiple times to see if it would help.
Most of the time the point of focus is within the depth of field, but often just barely. Since the lens front and back focused about equally, I decided to leave the microfocus adjustment at zero.
I'm not hearing good reports on the autofocus of the 50 Art lens, so I guess I will just keep enjoying the timeless rendition of the Classic until Canon eventually comes out with their next 50.