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04-26-2009, 12:48 PM   #1
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get autofocus capability for your manual lenses!

Some ebay sellers (of Pentax SMC F 1.7X AF Adapter) declare that:

When mounted between an autofocus body and either a Pentax A type or M type lens, the adapter converts the lens into an autofocus lens.

The focusing mechanism is fast and snappy. no problem with Pentax SMC A 50mm f1.7 lens & Pentax SMC A 28mm f2.8 lens,

Is it possible? Anybody test it?




04-26-2009, 01:02 PM   #2
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There are a bunch of people on here that report that it will get you close to focus but you will need to manually lock it in.
04-26-2009, 01:04 PM   #3
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Yes, this is true. There's a thread discussing this somewhere not so long ago...
04-26-2009, 01:05 PM   #4
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I own one, and yes, it's true ... sort of. With a long lens, you have to manually focus somewhere near, then the converter will fine tune the focus for you. It even works in good light and high contrast with my M 400mm f/5.6. Anything less and it just hunts and gives up. As it is stated to work only with lenses f/4 and faster, I cannot complain. There is a thread where I posted my results on a wintry day.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/56876-i-bored-m400-af1-7x.html


Last edited by Damn Brit; 04-28-2009 at 06:29 PM. Reason: Fixed Link
04-26-2009, 02:28 PM   #5
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Page not found...
04-26-2009, 03:10 PM   #6
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QuoteOriginally posted by fs999 Quote
Page not found...
I see that - I redid the link, but it still does not work. In lenses, look for "I was bored m400 + af1.7" in the threads.
04-28-2009, 06:11 PM   #7
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Which ebay seller have this? I never seem to find these TC's when I look.
04-28-2009, 06:19 PM   #8
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QuoteOriginally posted by Canada_Rockies Quote
I see that - I redid the link, but it still does not work. In lenses, look for "I was bored m400 + af1.7" in the threads.
Albert,I took the liberty of fixing your link.


Last edited by Damn Brit; 04-28-2009 at 06:30 PM.
04-28-2009, 06:22 PM   #9
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eBay link

Says he has 10 of them.

Last edited by G_Money; 04-28-2009 at 06:28 PM.
04-28-2009, 06:51 PM   #10
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The SMC-F 1.7x AF TC is an excellent teleconverter. I use it quite a bit on my SMC 300mmF4. Note that while the instructions state it must be used with lenses F2 and faster, it works very well up to F4. F4.5 is reported to work, but I have no experinece at that apature with it. I know F5.6 just does not work except in bright sunlight.

I would be careful about " close focusing claims. while the adaptor clearly will be able to focus closer than your normal 50mm lens, it will only give about a 20% reduction in close focus distance on a 50mm lens, and the longer you go with prime lenses the smaller the reduction in close focus is. that is just optics. It is not meant to replace close upl lenses or extension tubes.
04-28-2009, 09:16 PM   #11
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QuoteOriginally posted by Damn Brit Quote
Albert,I took the liberty of fixing your link.
Thanks. What had I done wrong?
04-28-2009, 09:19 PM   #12
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QuoteOriginally posted by Lowell Goudge Quote
The SMC-F 1.7x AF TC is an excellent teleconverter. I use it quite a bit on my SMC 300mmF4. Note that while the instructions state it must be used with lenses F2 and faster, it works very well up to F4. F4.5 is reported to work, but I have no experinece at that apature with it. I know F5.6 just does not work except in bright sunlight.

I would be careful about " close focusing claims. while the adaptor clearly will be able to focus closer than your normal 50mm lens, it will only give about a 20% reduction in close focus distance on a 50mm lens, and the longer you go with prime lenses the smaller the reduction in close focus is. that is just optics. It is not meant to replace close upl lenses or extension tubes.
But it will crop the subject by 1.7, which might be what was meant. My next project will be to see how it works with my M 100 macro. It might just give me an edge. A 170mm f/6.8 macro lens, all Pentax glass.
04-29-2009, 02:34 AM   #13
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QuoteOriginally posted by Canada_Rockies Quote
But it will crop the subject by 1.7, which might be what was meant. My next project will be to see how it works with my M 100 macro. It might just give me an edge. A 170mm f/6.8 macro lens, all Pentax glass.
of course it crops by 1.7x after all it is a teleconverter, to my knowledge there is no 1:1 autofocusing adaptor for any camera. It needs to have magnification because im the adaptor changes the mount to focusing plane distance.

as for the SMC-M100 F4, it works just fine, I have one.
04-29-2009, 03:13 AM   #14
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I don't understand this... a pure MF lens doesn't have any built-in mechanics for AF, the only way to focus is to turn the focusing ring with your hand. How can a TC make it AF?? Or is it that the TC have some moving optical element used for focusing?
Enlighten me please
04-29-2009, 03:40 AM   #15
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QuoteOriginally posted by simico Quote
I don't understand this... a pure MF lens doesn't have any built-in mechanics for AF, the only way to focus is to turn the focusing ring with your hand. How can a TC make it AF?? Or is it that the TC have some moving optical element used for focusing?
Enlighten me please
one more question:
Does it work for instance with a M42 lens?
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