Monday, November 8, 2004, 12:39:45 AM, Alan wrote:
AC> Many people have reported some Sigma lenses took longer to lock focus (tend
AC> to hunt more). It seems that the distance and focal length data are required
AC> for AF as well, and those data are held by a chip inside the AF lenses.
Probably. I had problems with a Sigma 1.8/28 (the old version, not the
EX one) in Nikon mount, it consistently frontfocused. On several
bodies. I previously thought that impossible, but apparently there is
now so much chips in lenses and cameras that even what looked like a
closed loop system (check focus, rotate by some computed amount from
FL and distance, recheck focus) can get buggy. But it was from a
period when Sigma lenses were quite buggy. Nowadays, they make the
software in them better I heard.
Good light!
fra
