New Sigma 120-400 OS dated
Posted 16/05/2010 - 16:08
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MrCynical wrote:
Sigma's HSM foible is in making them focus accurately in the first place (see Sigma 50mm f1.4 for further reading!) As far as I can tell if you get a Sigma lens that accurately focuses to begin with, its HSM motor will not break like SDM are reported to.
From what I hear it's not actually the SDM that breaks most of the time but the mechanism behind it gets jammed because it's out of alignment, at least that's what I've read what was suppose to be an official message from Pentax on the forum.Sigma's HSM foible is in making them focus accurately in the first place (see Sigma 50mm f1.4 for further reading!) As far as I can tell if you get a Sigma lens that accurately focuses to begin with, its HSM motor will not break like SDM are reported to.
I'm thinking the KAF2 mount is simply faulted by his complexity and that the KAF3 mount will preform better.
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 16/05/2010 - 21:52
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Anvh wrote:
I'm thinking the KAF2 mount is simply faulted by his complexity and that the KAF3 mount will preform better.
It has been suggested in quite a few places that it is the gearing that fails rather than the motor, but KAF3 doesn't change that. The KAF3 lenses (such as the DA*55) still have gearing between an SDM motor and the lens elements (compared to for example Canon's 'ring USM' which drives the elements directly).
I'm thinking the KAF2 mount is simply faulted by his complexity and that the KAF3 mount will preform better.
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965 posts
17 years
Glasgow
you sure?
There aren't many lenses with HSM for Pentax that's one reason we don't hear much about it on this forum.
I've no idea how it is on Canon or Nikon forums.