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09-04-2009, 02:00 AM   #1
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Has anyone used a stabilized Sigma lens with their Pentax yet?

I'm curious if it actually works. And if it does.. how does it manage to do it without the proper contacts?

09-04-2009, 11:12 AM   #2
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QuoteOriginally posted by ftpaddict Quote
I'm curious if it actually works. And if it does.. how does it manage to do it without the proper contacts?
Won't work, but it won't shut off your SR either.
09-04-2009, 01:21 PM   #3
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QuoteOriginally posted by ftpaddict Quote
I'm curious if it actually works. And if it does.. how does it manage to do it without the proper contacts?
It doesn't need any "proper contacts" as long as the lens has its own accelerometer. Just shut off the camera's SR and should work just as well. Haven't used though.
09-04-2009, 01:48 PM   #4
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QuoteOriginally posted by kristoffon Quote
It doesn't need any "proper contacts" as long as the lens has its own accelerometer. Just shut off the camera's SR and should work just as well. Haven't used though.
And where does the power for the compensating thingie come from?

09-04-2009, 03:15 PM   #5
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QuoteOriginally posted by ftpaddict Quote
And where does the power for the compensating thingie come from?
I don't know if it works or not, but power should at least be available. After all, the SDM lenses gets power some how.
09-04-2009, 03:27 PM   #6
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QuoteOriginally posted by kjellhar Quote
I don't know if it works or not, but power should at least be available. After all, the SDM lenses gets power some how.
BUT Pentax does not have the power supply for those lenses. Nada. Won't work. Waste of money if you have a Pentax/Samsung body, or anything else. BTW, I believe you would need a specific Pentax K mount lens, and it would not include the VR/IS/whatever.
09-05-2009, 12:31 AM   #7
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QuoteOriginally posted by kjellhar Quote
I don't know if it works or not, but power should at least be available. After all, the SDM lenses gets power some how.
The SDM motors get their power from the two special contacts from inside the bayonette mount. These contacts would not be sufficient to power an in-lens stabilization system, as the body only provides power through these contacts during focusing operations. The body also switches polarity accordingly, to move the focus point closer or farther away.
09-05-2009, 01:49 AM   #8
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I was under the impression that in-lens stabilisation required no power as essentially suspension for the optical system, like suspension for a car, so that the optical elements stay more centred on the sensor. Or am I wrong?

I would like to try the Sigma system & if I ever get a travel lens (18 to 250mm type) then I would look for that. I like having in-body stabilisation but from reviews I understand that Pentax's isn't the best (apparently Oly's is better) so I would give it a try. For me, this is the way to go - in body stabilisation so that every lens benefits and some lenses being available with in-lens stabilisation for those who choose to pay more or that it might be better.

FYI, Tamron now have a similar system & they are releasing a new version of the 17-50/2.8 but from what I've heard it'll only be for Canon & Nikon, as all other systems have in-body.

09-05-2009, 02:18 AM   #9
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QuoteOriginally posted by ftpaddict Quote
The SDM motors get their power from the two special contacts from inside the bayonette mount. These contacts would not be sufficient to power an in-lens stabilization system, as the body only provides power through these contacts during focusing operations. The body also switches polarity accordingly, to move the focus point closer or farther away.
You may be right about the fact that the power supplied through the SDM power pins are not enough, but I'm pretty sure the polarity does not change to reverse the rotation of the focus motor. Do you know that as a fact? Any real references to back it up?

The ring type motor used in these kinds of lenses works in a very different way than the ordinary DC motors that most people know. They won't do anything if you just apply power. You need to have some controller electronics as well to make it happen. I can't find any references right now, but if you're interested in how it works, I google search including something like "How USM motor works" will probably give you some results. If I were to explain it myself, I need to make some drawings.
09-05-2009, 02:31 AM   #10
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QuoteOriginally posted by Jonathan Mac Quote
I was under the impression that in-lens stabilisation required no power as essentially suspension for the optical system, like suspension for a car, so that the optical elements stay more centred on the sensor. Or am I wrong?
No, only the very first Canon prototypes of the optical image stabilization worked that way. A purely mechanical systems is too bulky and too expensive - and too slow to compensate the minute, quite fast vibrations of a handheld lens (because of the inherent momentum of the parts). Adjusting the lens groups via motors/piezos or whatever is much cheaper and can be made smaller. Also, you need power for the accelrometers to actually measure, how much the optical groups need to be shifted.

Ben
09-05-2009, 08:18 AM   #11
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QuoteOriginally posted by Ben_Edict Quote
No, only the very first Canon prototypes of the optical image stabilization worked that way. A purely mechanical systems is too bulky and too expensive - and too slow to compensate the minute, quite fast vibrations of a handheld lens (because of the inherent momentum of the parts). Adjusting the lens groups via motors/piezos or whatever is much cheaper and can be made smaller. Also, you need power for the accelrometers to actually measure, how much the optical groups need to be shifted.

Ben
Ahh, so they move the optics in much the same way as in-body systems move the sensor.
09-05-2009, 09:03 AM   #12
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QuoteOriginally posted by Jonathan Mac Quote
Ahh, so they move the optics in much the same way as in-body systems move the sensor.
the principle is the same. But ofcourse the motor in the lens needs more torque and probably a longer travel. But that depends very much on the lens construction.

Ben
09-05-2009, 10:28 AM   #13
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QuoteOriginally posted by ftpaddict Quote
And where does the power for the compensating thingie come from?
From the same contacts that power the in-lens chips for determining focal length, aperture, etc
09-05-2009, 01:44 PM   #14
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Based on my experiences with power-zoom lenses on my K10, I am of the opinion that the SDM/PZ contacts should provide enough power for the in-lens stabilization system, and not just during focusing. If they can provide enough power to zoom the old heavy 100-300 power zoom lens, they should be able to move one or two small pieces of glass. remember, these contacts were originally designed for providing stable power to the power-zoom lenses, and the fact that they still power zoom on the k10 tells me that the electrical capabilities have not been altered.

From Sigma's own website:

"For Sony and Pentax mount, the built-in OS function of this lens can be used even if the camera body is equipped with an anti-shake function"

and

"For Pentax and Sony mount, it is not possible to use AF and the stabilizer function (OS) when attaching to film SLR, Pentax ist* series and K100D DSLR cameras."

Which tells me that it does indeed get it's power through the SDM/PZ contacts.

Edit: while it says it won't work on film SLRs, if it does indeed get it's power through the SDM/PZ contacts, I wonder if it would work on the PZ series and the MZ-S?
09-05-2009, 04:15 PM   #15
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Also from Sigma's website
QuoteOriginally posted by Sigma's Website:
For Sony and Pentax mounts the built-in OS System allows the photographer to see the stabilized image in the viewfinder and can be used as an alternative with cameras having built-in image stabilization...

When the OS function of lens body is used, please turn the stabilizer function of camera body off.
Looks like an answer to your question. I took this from the Sigma 50-200mm lens page.

Last edited by Rich_A; 09-05-2009 at 04:30 PM.
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