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07-29-2010, 02:06 AM   #1
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Sigma hsm

is the concept of HSM on Sigma Lenses
the same as that of the SDM?

07-29-2010, 03:55 AM   #2
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Yes.

But my post is too short, so let me rephrase.

In a word, yes.
07-29-2010, 05:02 AM   #3
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QuoteOriginally posted by MPrince Quote
Yes.

But my post is too short, so let me rephrase.

In a word, yes.
I'm sorry but I'm a busy man and don't have time for an extended read--could you summarize?
07-29-2010, 05:13 AM   #4
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So what's the talk about the Sigma ring HSM motor as opposed to a micromotor-SDM? Is it only in some lens models?

07-29-2010, 05:22 AM - 1 Like   #5
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QuoteOriginally posted by dadipentak Quote
I'm sorry but I'm a busy man and don't have time for an extended read--could you summarize?
I'd be happy to.

The op wanted to know if, conceptually, Sigma HSM is equivalent to Pentax SDM.

I replied in the affirmative, however, the forum does not permit short posts, therefore, in order for my post to be accepted, I had to greatly expand on my initial response. I did so by adding more words, without altering the meaning of my initial reply, which was a simple yes.

The reason I initially went with such a simple, one word response was because it seemed to me that the nature of the original question did not really call for an elaborate response, and I believed that a simple, short answer would be sufficient.

After all, the op didn't ask for a detailed comparison of the exact specifications for HSM and SDM along with similarities, differences, effectiveness of one versus the other, etc. He just wanted to know if the concept was the same.

Which they are.

AFAIK

07-29-2010, 05:27 AM   #6
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QuoteOriginally posted by emr Quote
So what's the talk about the Sigma ring HSM motor as opposed to a micromotor-SDM? Is it only in some lens models?
I have no clue. I just know the concept is the same. A way of implementing auto-focus by means other than a screw drive.

But really, what do I know? After all, I drive a car yet I have no clue how to re-build an engine, and I can tell time but don't know how to construct a clock mechanism.

07-29-2010, 05:29 AM - 1 Like   #7
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HSM - Hyper-Sonic Motor
SDM - Silent Drive Motor

They are similar in that they operate a lot quieter than screw driven lenses.
They are different in that SDM is a micro-motor design, while HSM can be either a ring-motor design (e.g. Sigma 70-200mm F2.8 EX DG HSM II), or a micro-motor design (17-50mm F2.8 EX DC OS HSM).
07-29-2010, 05:55 AM   #8
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thanks for the responses!

now I know the concept is the same
anyone tried Sigma lenses with HSM?

is it faster than SDM when it comes to focus?

07-29-2010, 06:42 AM   #9
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In a word, yes. But it depends on the particular lens in question.
07-29-2010, 06:59 AM   #10
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lets say
the

Sigma 17-70 HSM

to

Pentax SMC DA*16-50 SDM ?
07-29-2010, 07:39 AM   #11
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I've never tried that Sigma so I can't comment specifically, but the 16-50 is pretty dang quick, especially after the new firmware for the K7.
07-29-2010, 08:18 AM   #12
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QuoteOriginally posted by redeleon Quote
thanks for the responses!

now I know the concept is the same
anyone tried Sigma lenses with HSM?

is it faster than SDM when it comes to focus?
I have the Sigma 150-500 HSM. It is a bit odd after listening to the grind and whine from Pentax lenses for the last few years. The only thing to show that it is focusing is...the focus changes.

I don't know if it is faster than Pentax but it probably can't be slower.

Last edited by SpecialK; 07-29-2010 at 02:40 PM.
07-29-2010, 09:10 AM   #13
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HSM = ring motor = bigger
SDM = micromotor = smaller

Bigger is generally faster :-)
07-29-2010, 09:33 AM   #14
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I have the sigma 17-70 but not the pentax 16-50 so I can't compare. The sigma focused fast before I upgraded the k-7 firmware, but i did the upgrade this morning and haven't had a chance to see if it's even faster now.
07-29-2010, 01:12 PM   #15
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QuoteOriginally posted by emr Quote
So what's the talk about the Sigma ring HSM motor as opposed to a micromotor-SDM? Is it only in some lens models?
The question was whether the *concept* was the same, not if they were completely identical. The concept is indeed the same in both - a motor within the lens does the focusing, as opposed to the more traditional method of having focus done by a motor in the body. But the specifics of the lens motor designs do indeed differ between Pentax SDM and Sigma HSM.
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