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Eruditass · 05-30-2010, 08:25 AM

I wonder how it would fare in a body with a weaker focusing motor (K-x, other AA battery bodies), although there is that new Algorithm which probably improves the slower lens more.

Too bad we can't try it out.

Last edited by Eruditass; 05-30-2010 at 08:52 AM.

KjetilH · 05-30-2010, 08:36 AM

I have read here on the forums that the camera is not "fooled" by taping over the SDM contacts. A few members have (two, at least) K20Ds that won't use the SDM , and defaults to screw drive. This is probably due to the SDM electronics being shorted and broken.

My guess is that the "digital info contact" in the KAF2 mount supplies information on whether to use SDM or screw drive. Insulating this won't work, though, and disables a lot of other information needed for the body.

Adam · 05-30-2010, 12:31 PM

AFAIK the two contacts only supply power for the SDM motor. The actual data is transmitted over the appropriate contact on the lens mount.

ytterbium · 06-05-2010, 08:52 AM

But what does it do, when it gets no power? Isn't it the same as if SDM circuit was down. Or it simply stays in SDM mode but wont focus.

Eruditass · 06-06-2010, 01:17 PM

Originally posted by ytterbium

But what does it do, when it gets no power? Isn't it the same as if SDM circuit was down. Or it simply stays in SDM mode but wont focus.

The latter, I believe.

05-30-2010, 08:36 AM	#17
KjetilH Veteran Member Join Date: Mar 2008 Location: Oslo Photos: Gallery Posts: 309	I have read here on the forums that the camera is not "fooled" by taping over the SDM contacts. A few members have (two, at least) K20Ds that won't use the SDM , and defaults to screw drive. This is probably due to the SDM electronics being shorted and broken. My guess is that the "digital info contact" in the KAF2 mount supplies information on whether to use SDM or screw drive. Insulating this won't work, though, and disables a lot of other information needed for the body. Last edited by KjetilH; 05-30-2010 at 09:00 AM.

05-30-2010, 12:31 PM	#18
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,609 Original Poster	AFAIK the two contacts only supply power for the SDM motor. The actual data is transmitted over the appropriate contact on the lens mount. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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05-30-2010, 08:25 AM	#16
Eruditass Veteran Member Join Date: Jul 2009 Photos: Gallery Posts: 2,207	I wonder how it would fare in a body with a weaker focusing motor (K-x, other AA battery bodies), although there is that new Algorithm which probably improves the slower lens more. Too bad we can't try it out. Last edited by Eruditass; 05-30-2010 at 08:52 AM.

06-05-2010, 08:52 AM	#19
ytterbium Veteran Member Join Date: Jan 2008 Posts: 1,076	But what does it do, when it gets no power? Isn't it the same as if SDM circuit was down. Or it simply stays in SDM mode but wont focus.

06-06-2010, 01:17 PM	#20
Eruditass Veteran Member Join Date: Jul 2009 Photos: Gallery Posts: 2,207	Originally posted by ytterbium But what does it do, when it gets no power? Isn't it the same as if SDM circuit was down. Or it simply stays in SDM mode but wont focus. The latter, I believe.

Pentax Screwdrive AF vs SDM AF compared! (on DA* 50-135mm)

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