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07-12-2009, 07:22 PM   #1
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Pentax SDM vs Sigma HSM. Which is better?

Anyone have lenses that are Sigma HSM and also own one or more Pentax SDM? I have a DA*16-50mm that has issues locking focus in what you would think are easy shots. It doesn't happen often and I don't fret over it but wondered if anyone has or owns both brands and can compare. Do the Sigma's have the same problem hunting for focus lock once in awhile?


Last edited by Peter Zack; 07-13-2009 at 06:20 AM.
07-13-2009, 03:04 AM   #2
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No one has tried both?
07-13-2009, 03:25 AM   #3
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Don't have any SDM lenses but...well...I have managed to lock the focus in very dimly lit room under one 40W lightbulb in a fraction of a second with 50-150 HSM II. Sometimes, however, the K20D + Sigma does hunt even in normal daylight conditions especially with distant targets. But when it hunts, it is usually max 1-2 corrections in *fast* succession and then it locks.
07-13-2009, 10:59 AM   #4
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I would love to try out the new Sigma 24-70mm f/2.8 IF EX DG HSM, but I don't have $900 bucks laying around ;-)

07-13-2009, 12:26 PM   #5
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I dont think HSM lenses work with Pentax, and Sigma have not produced any lenses with SDM. So, unless you are working with more than one system, the two are mutually exclusive.

i.e. you can't compare the two directly

or am I wrong?
07-13-2009, 01:34 PM   #6
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QuoteOriginally posted by keithlester Quote
I dont think HSM lenses work with Pentax
You're wrong
07-13-2009, 02:25 PM   #7
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What is better in this case?

I tried both hsm and sdm in a show last year, on my k10d, so i could be wrong.


HSM moves the focus ring faster. No arguing about that. However, to achieve the "perfect" focus, it moves 3 or 4 times. First time to "roughly" focus, then fine tuning.

SDM, however, does it in 2 or 3 times. Yes, it moves slower, but as it moves less times than HSM, the focusing time is about the same.


If better is "focuses faster", I would say there is no clear winner. Maybe HSM, if you're outside, with a bright sun (but i can't say for sure, as i tried both inside a big hall, so the sun was... well, quite well hidden).
If better is "right in focus", i don't know, i believe both systems can achieve that (even if sigma has some qc issues, if what the retailers i talked with are right).
07-13-2009, 02:32 PM   #8
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QuoteOriginally posted by kenyee Quote
You're wrong
You're both right. There are a lot of them that don't, but the newer ones do.

07-13-2009, 03:46 PM   #9
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i've been looking into sigma hsm lenses and so far i've seen announcements of them for the pentax mount but no 1st-hand reviews whatsoever of released lenses.

this is the one i am interested in:
Sigma - Lenses

Sigma's Note: "For Pentax mount, if the camera body does not support HSM, auto focus will not be available." so it will definitely uses HSM...
07-13-2009, 03:58 PM   #10
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I have two SDM lenses (16-50 and 50-135) and I tried the Sigma HSM 150-500 (due to their sponsoring and loaning lenses to the East-Coast Gathering put on by BrendanPK at the Blackwater wlp - thanks Sigma!). It wasn't a very good comparison really due to the shear size differences in the lenses. I have to say that the Sigma was buttery smooth and silent in it's focusing but was rather slow compared to my SDM lenses. But it's a huge lens and size alone could account for the difference. I was also using it on a K10D.

Now I have to say that my SDM lenses on my K-7 are soooo much faster, and when I shoot both cameras in the same shoot, both with SDM lenses, the one on the K10D feels very slow. So I'm itching to try that 150-500 on my K-7 now to see how much faster to focus it might be. I really really liked that lens. I want to buy one.
07-13-2009, 07:22 PM   #11
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QuoteOriginally posted by Peter Zack Quote
Anyone have lenses that are Sigma HSM and also own one or more Pentax SDM? I have a DA*16-50mm that has issues locking focus in what you would think are easy shots. It doesn't happen often and I don't fret over it but wondered if anyone has or owns both brands and can compare. Do the Sigma's have the same problem hunting for focus lock once in awhile?
I don't think focus drive technology would make a difference... after all it does nothing more than turn the ring back and forth on the body's command. I'd guess either your body has a problem, or your lens. Or, perhaps, neither and that's normal behaviour you're experiencing.
07-13-2009, 07:56 PM   #12
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There were several of us on another thread discussing SDM and this odd behaviour it will sometimes show. It just hangings up and won't focus. The contrast is good and the light fine. The lens just refuses to focus. I'm not the only one that has had this issue. It doesn't happen often and there's no rythm to it. Ring motors certainly are more powerful and that may be the difference. As for the 4 bodies I have and good selection of lenses. The cameras have no issue with all my other glass.

Interestingly the *istD is screw drive only and the DA*16-50mm never hangs up on that body. Only on my other SDM enabled bodies.
07-13-2009, 08:00 PM   #13
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I have the DA*300mm and the Sigma 70-200 HSM--like 'em both. I haven't given much thought to this sort of comparison (partly because they're both better lenses than I am a photographer but also because I tend to use them for fairly distinct subjects and situations) but what Viggen says seems about right (but I'd note that Pentax seems to have had its qc issues as well.)

In practice, I find I often go MF with the DA*300 but that's because I'm shooting birds in bushes ;~)
07-13-2009, 08:00 PM   #14
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QuoteOriginally posted by Peter Zack Quote
Interestingly the *istD is screw drive only and the DA*16-50mm never hangs up on that body. Only on my other SDM enabled bodies.
As an experiment, can you put a piece of electrical tape over the SDM contact if there is such a thing? Then the body should think it's not an SDM lens?
07-13-2009, 08:33 PM   #15
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QuoteOriginally posted by Peter Zack Quote
There were several of us on another thread discussing SDM and this odd behaviour it will sometimes show. It just hangings up and won't focus. The contrast is good and the light fine. The lens just refuses to focus. I'm not the only one that has had this issue. It doesn't happen often and there's no rythm to it. Ring motors certainly are more powerful and that may be the difference. As for the 4 bodies I have and good selection of lenses. The cameras have no issue with all my other glass.

Interestingly the *istD is screw drive only and the DA*16-50mm never hangs up on that body. Only on my other SDM enabled bodies.
I've never had a hang with the 16-50, but had some with the 50-135 that seems to be a bit more prone to it. I'm hanging on until the warranty is almost done before I send it in.
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