Adam Maas wrote on 12.01.06 16:20: > The 28-105 isn't RF, it's IF just like the Tamron. I have the lens in > front of me and checked, rear element's don't move, you can see the > elements behind the first group move when focusing. The elements > themselves might be heavier in the Tamron, but the overall build is much > lighter, and I'd assume that applies to whatever is holding the focusing > elements as well. The Canon lens in question is heavily built with a > metal barrel, especially for a 'consumer' zoom. You might be thinking of > the 28-105 f4-5.6 USM, which is a cheaply built lens and may be RF. I was always sure that 28-105/3,5-4,5 is RF lens, but of course I might be wrong. And I think 28-105 f4-5,6 is not IF neither RF - it is cheapo consumer zoom :-)
> Unfortunately the module does enter into the equation, unless you are > able to do a infinity-close focus test. Which is why I've made a point > to note what camera/sensor I've been using. If module enters into equation, than it is impossible to compare speed of USM and screwdriver style AF systems. USM lens coupled to bad AF circuit in camera can be much worse than good AF module + screwdrive type lens.... > I'm not sure of the speed of > the HSM motor in the Sigma's, it may not be up to the Canon or Nikon's. > Can't say, I haven't tried it. Can't say either... But again. We would have to have two identical lenses like this Sigma - one equipped with HSM motor, second with USM one. I guess it is impossible :-) BTW - at the time when I had D70 which we were comparing with Dario to *istD, I had F100 too. Both cameras had similar AF speed with Sigma in good light. No AF module, neither built-in motor of course have influence on speed of HSM motor :-) -- Balance is the ultimate good... Best Regards Sylwek
