Originally posted by Gooshin just thinking outloud
and lets take the K100D here since it uses AA's
wouldn't auto focusing a gigantic lens drain the batteries very fast?
I have an *istD and the sigma 70-200 F2.8, which I use a lot with a 1.4x TC
This is a screw drive lens, hence big fast and I think would fit the criteria of "draining the batteries very fast"
It does not! I have never had an issue with loss of batteries even when taking several hundred photos. Instant review and pixle peeping on camera use A LOT MORE.
IF lenses were developed specifically to reduce the mass of the elements focused, and therefore reduce power. USM or what ever each maker calls it is even more efficient.
In fact I believe a lens like my sigma 10-20, which has the focusing collar driven full time (due to volume restrictions on the lens) probably takes more power