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02-19-2013, 04:47 PM   #1
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Autofocus on adapted Pentax lenses that have an SDM motor

Please help a noob understand something. While showing the girlfriend how cool it was to mount my DA 18-135mm lens on the Q she asked the simple question that I just don't have an answer for. So, why can't auto-focus be used on an adapted lens that is a K mount and has an internal motor? I have done some searching around but can't find a clear answer. It has to be more to it than just having the correct "pass through" contacts doesn't it? Does it have to do with not "knowing" the lens and having the programming to control it properly? If so, would't that just be a few more contacts and a firmware upgrade? I do understand that the niche of using adapted lenses on the Q is fairly limited so perhaps there is just no motivation for Pentax to make it work? Thanks.

02-19-2013, 04:51 PM   #2
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I would start here:

https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ce-thread.html

and that is a good question you are asking as I also have a couple of SDM-lenses;
I know that there is a post(s) somwehere in that thread about the DA*300/4 (SDM) .... I haven't checked it out yet.

JP

Edit: here's the post about the DA*300/4 ... https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ml#post2215855
and one more here (post 242): https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ml#post2268701

Not sure whether this will answer your question but someone more knowledgeable will surely jump in with the proper answer.
02-19-2013, 04:55 PM   #3
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I think it could also be the amount of power needed, as the Q is already starved just trying to power itself and the native AF lenses.
The engineers probably determined the little Q battery could not handle it.

(Why not a battery in the adapter? Or a solar powered one for daylight use?)
02-19-2013, 04:56 PM   #4
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QuoteOriginally posted by colonel00 Quote
Please help a noob understand something. While showing the girlfriend how cool it was to mount my DA 18-135mm lens on the Q she asked the simple question that I just don't have an answer for. So, why can't auto-focus be used on an adapted lens that is a K mount and has an internal motor? I have done some searching around but can't find a clear answer. It has to be more to it than just having the correct "pass through" contacts doesn't it? Does it have to do with not "knowing" the lens and having the programming to control it properly? If so, would't that just be a few more contacts and a firmware upgrade? I do understand that the niche of using adapted lenses on the Q is fairly limited so perhaps there is just no motivation for Pentax to make it work? Thanks.
See Crew's1 post just above.
That would make sense.

JP

02-19-2013, 04:58 PM   #5
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Sony doesn't have a reliable AF A to E adapter either. They have a $200 adapter that doesn't AF, and a $400 adapter that adds an entire mirror assembly and phase detect AF sensor.
02-19-2013, 04:59 PM   #6
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QuoteOriginally posted by colonel00 Quote
Please help a noob understand something. While showing the girlfriend how cool it was to mount my DA 18-135mm lens on the Q she asked the simple question that I just don't have an answer for. So, why can't auto-focus be used on an adapted lens that is a K mount and has an internal motor? I have done some searching around but can't find a clear answer. It has to be more to it than just having the correct "pass through" contacts doesn't it? Does it have to do with not "knowing" the lens and having the programming to control it properly? If so, would't that just be a few more contacts and a firmware upgrade? I do understand that the niche of using adapted lenses on the Q is fairly limited so perhaps there is just no motivation for Pentax to make it work? Thanks.
The adapter has neither the necessary power contacts or data contacts needed to enable AF on adapted lenses. Plus, even if AF were enabled, it would be very very slow due to the CDAF, so I don't think you're missing out on much!

Adam
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02-19-2013, 05:00 PM   #7
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QuoteOriginally posted by jpzk Quote
I would start here:

https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ce-thread.html

and that is a good question you are asking as I also have a couple of SDM-lenses;
I know that there is a post(s) somwehere in that thread about the DA*300/4 (SDM) .... I haven't checked it out yet.

JP

Edit: here's the post about the DA*300/4 ... https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ml#post2215855
and one more here (post 242): https://www.pentaxforums.com/forums/pentax-q/209474-adapted-lenses-tested-q-r...ml#post2268701

Not sure whether this will answer your question but someone more knowledgeable will surely jump in with the proper answer.
Thanks. I have been following that thread closely and enjoy what people are doing with all of the lenses. Still though, even with the official Pentax adapter, auto-focus is not an option.

QuoteOriginally posted by crewl1 Quote
I think it could also be the amount of power needed, as the Q is already starved just trying to power itself and the native AF lenses.
The engineers probably determined the little Q battery could not handle it.

(Why not a battery in the adapter? Or a solar powered one for daylight use?)
Now this is a very interesting point and thanks for chiming in. I had not thought about the power requirements. Does the Q really struggle that much with its native lenses? I have not had mine long enough to get some good time on with it.
02-19-2013, 05:09 PM   #8
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QuoteOriginally posted by boriscleto Quote
Sony doesn't have a reliable AF A to E adapter either. They have a $200 adapter that doesn't AF, and a $400 adapter that adds an entire mirror assembly and phase detect AF sensor.
QuoteOriginally posted by Adam Quote
The adapter has neither the necessary power contacts or data contacts needed to enable AF on adapted lenses. Plus, even if AF were enabled, it would be very very slow due to the CDAF, so I don't think you're missing out on much!
Thanks. Perfect answers I was looking for. Once I had the right search terms it was easy to find the answers by looking up the Metabones product for the Sony Nex. Right at the bottom of the page about the Canon lens to Nex body adapter page it states it pretty clearly:

QuoteQuote:
Autofocus

Autofocus is supported, with the following known limitations.

Autofocus speed is very slow and inadequate for most moving subjects. The autofocus speed is unfit for professional use for sure, and it would disappoint most enthusiasts.


02-19-2013, 05:20 PM   #9
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QuoteOriginally posted by colonel00 Quote
Thanks. I have been following that thread closely and enjoy what people are doing with all of the lenses. Still though, even with the official Pentax adapter, auto-focus is not an option.



Now this is a very interesting point and thanks for chiming in. I had not thought about the power requirements. Does the Q really struggle that much with its native lenses? I have not had mine long enough to get some good time on with it.
It doesn't struggle but it eats up batteries quicker than other cameras. It is recommended to bring extra batteries on a photo outing with the Q.
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