Skip <[EMAIL PROTECTED]> wrote: > I have the Sigma 15mm fisheye and the 17-35 f2.8-4 EX HSM, and while they are as > optically good as on could expect for distortion prone types, the 17-35 focuses > pretty slowly. I have no experience with other Sigmas, but if this one is a > "High Speed Motor," then the others must pe pretty pedestrian. It is much slower > than, say, my 28-135 IS. > Skip
Skip, The HSM in the Sigma 17-35 f/2.8-4.0 HSM EX is what Sigma refers to as "micro-HSM," which like Canon's "micro-USM" is cheaper than true ultrasonic or 'hypersonic' motors. Neither 'micros' allow full time manual focus, unlike Canon's ring-USM or Sigma's non-micro HSM. I haven't used any other Sigma lens to be able to compare their non micro HSM with Canon's ring USM. Bill Jameson * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
