Originally posted by ggascay I am comparing the noise to my only other SDM lens, the 18-135, which is nearly silent and has more of a faint "whirring" sound. In contrast, the DA*300 is much louder and more abrupt and does not sound right.
The 18-135 is not SDM but a DC Motor lens. I don't have a DA*300 but do have other DA* lenses that still run on SDM (16-50 and 55 1.4). The latter is an SDM only (KAF3) without screw drive option. They both "squeak" a bit during focusing especially at the point where motor takes-off or stops when it locks focus. I do have an 18-135 as well and if I were to compare the AF noise against DA*, to me they're about the same except that 18-135 doesn't squeak at all.