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09-05-2009, 08:53 PM   #16
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Image stabilization does indeed work on Sigma lenses when mounted on Pentax cameras. The only glitch is that you have to choose either Sigma's optical stabilization or Pentax's sensor stabilisation, but not both as they are incompatible.

If you don't believe me, just go to the nearest Pentax dealer and try a Sigma stabilized lens: it is pretty obvious from the view in the finder that the optical stabilization is working.

Cheers!

Abbazz

09-06-2009, 09:07 AM   #17
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Abbazz, thanks for the confirmation! I would note, however, that not all Sigma lenses with OS work on the Pentax system...

For example on the 150-500mm lens page it quotes:
QuoteQuote:
*OS function is not available for Sony/Minolta or Pentax cameras.
I would like to see Sigma publish a compatibility page for Pentax users to provide a definitive guide to their current lineup so the confusion is resolved.
09-06-2009, 12:43 PM   #18
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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.
The camera provides power through these contacts for any lens that requires it, otherwise as pointed out by clawhammer, our power zooms wouldn't work. I tried but couldn't measure any voltage across these contacts and suspect the any lens that requires power will tell the camera via the digital information contact. I also suspect (but can't confirm) that the control for the SDM lenses is supplied through the digital contact.

QuoteOriginally posted by Ben_Edict Quote
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
It does depend a lot on the lens design / construction. In some lenses there will be a small and relatively light lens element that will be moved to provide the stabilisation. This could quite easily be lighter and easyer to move around than the sensor in the camera (especially as it won't need a bundle of wires to connect it to the rest of the camera) and so would probably take less power. Also depending on the optical power of the lens element it may require considerably less movement to correct vibration.

There are advantages to having the shake reduction in the lens, it means that it has been designed and optimised to work properly with that specific lens. I have to say that the Pentax SR is excellent and I don't know how I ever managed without it (lots missed, motion blurred shots). However it is a bit of a jack of all trades as it has been designed to work with any lens you can mount on the camera, which gives it significant advantages over other lens only based SR systems especially for the M42 crowd. I suspect that lens based SR will work better, in particular with long telephotos, but it significantly increases the cost and complexity of the lenses. It could well be that for special purpose lenses such as super telephotos, in lens SR will become common even for Pentax.
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