Originally posted by bassek If you need to take pics in the dark (like while driving out from camp, or at the camp fire) then AF is not accurate. Go MF. I ended up with my A50/1.7 wide open in those situations in Kenya.
Seb
The very fine Sigma 17-50mm f/2.8 EX DC has a very handy AF/MF switch, as good or better than Quick-shift. It delivers very good results even wide open, and even yet better at edges with just a little stop-down to f/3.2 or so. A very useful lens, and a bargain to boot.
Unlike the DA* 50-135mm f/2.8 It is apparently not a fully internal-focus design, so although the filter end does not rotate upon focus, the focus collar does rotate in both MF and AF. So you must be mindful of keeping your fingers out of the way during AF. This is not really inconvenient, as this is not a tiny lens like the screw-driven limiteds, so once mindful it is still easy to hold. An advantage could be not having the "focus-breathing" factor, so there'd be no reduction in effective focal length for portraits or closeups. And, its close focusing capabilities are exceptional, even for wide angle!
---------- Post added 09-03-19 at 04:57 PM ----------
Originally posted by UncleVanya The 20-40 is just too limited.
Excellent pun, UncleVanya!