Lots of New Sigma Lenses w/ HSM!

Old old old news...

I should have known better than to click on this.

Secondly.. all these new designs look like they are MICRO-HSM, not ring HSM. There is a big difference. See Canon's implementation of micro USM vs ring USM.

Sigma's got many a good ring HSM design (70-200, Bigma are those I've personally used), but it appears that this more expensive, robust, and faster focusing design will not make it to these smaller lenses.

^The last statement hardly makes sense seeing how Simga has HSM on there 10-20 and other UWA/fisheyes which makes no sense including that of keeping it off such lenses like the 17-70 and 18-50.

Wow very interesting, thanks for the further information about the D40 and all. Makes sense now.

The NIKON f mount wasn't changed for AF and other stuff, unlike Canon. The D40 will only AF with lenses that have it's own drive motor. It makes a great starter camera because it's affordable and simple. People who want AF on all their lenses are hereby directed to the D80 or above.

_aravena wrote in post #4379937
^The last statement hardly makes sense seeing how Simga has HSM on there 10-20 and other UWA/fisheyes which makes no sense including that of keeping it off such lenses like the 17-70 and 18-50.

Cost, plus easy 'upgrades' of these models without forcing a redesign.

Canon's explanation of micro HSM indicates that it is a drop-in upgrade whereby you simply replace a traditional DC motor with a micro HSM unit. You retain the geartrain (which ring USM lacks, being a direct-drive system). You retain the existing focusing rings, the lack of FTM, and the lack of a distance window.

The last 3 are giveaways that it'll be micro HSM. Looking at the photos I notice the new HSM equipped lenses lack all of the above. Specs for Sigma's ring-HSM lenses indicate FTM capability as well. Due to the existence of a geartrain in micro HSM, it cannot support FTM. (same for Canon's micro USM). Due to the design of ring HSM, it requires a distance window because the outer focusing ring (that you grip) can be disengaged from the internal focusing system. Can't do that without a distance window as it would be inaccurate after a couple of focusing attempts.

So why not simply use a traditional DC motor to keep costs down even further, just like the rest of the Sigma lenses in Canon mount (which by design, MUST have their own AF motors in the lens - no Canon has ever had the 'screwdriver' and AF motor in body). Dunno. Probably HSM sounds catchier. Maybe there is some camera-to-lens communication protocol issue that makes it easier to implement a HSM drive system than a DC focusing drive.

Of course, I hope I'm wrong and that we see ring HSM come out, followed by Canon mount versions. Then I'd buy

According to a post in dpreview Sigma has plans to produce a 17-70 HSM with Canon mount, see:

http://forums.dpreview​.com …rum=1029&messag​e=25743621