> > > 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 >
Hey Bill, There is a Canon micro-USM that allows FTM, the EF 50 1.4USM but this is the exception AFAIK from Canon. Regards, Chip Louie * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
