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07-16-2014, 02:54 PM   #1
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Older K Mount lens: Will they Autofocus?

I have a K-X and I know that older Pentax lenses will mount to the body. However, will the K-X's auto-focus system work with older lenses? If there is an age limit, what is the general date where the K-X's will no longer auto-focus the lens?

Thank You.

07-16-2014, 02:59 PM   #2
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If a Pentax-brand lens does not say F, FA, or DA on the front, it is a manual focus lens. Similarly, most 3rd-party AF lenses are prominently labeled as such. Proof positive is the presence/lack of the AF drive fitting an/or the AF contacts on the mount.

When using manual focus, you still have the option of focus confirmation. The AF system will signal when it has determined that focus has been attained. Focus confirmation is limited to the center spot focus sensor.


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07-16-2014, 03:01 PM   #3
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QuoteOriginally posted by dmfw Quote
I have a K-X and I know that older Pentax lenses will mount to the body. However, will the K-X's auto-focus system work with older lenses? If there is an age limit, what is the general date where the K-X's will no longer auto-focus the lens?

Thank You.
All AF Pentax lenses (with the exception of the M-era AF 35-70mm F2.8) are fully supported by the K-x, so you don't have to worry about compatibility.

AF lenses include the F, FA, FA J, D FA, DA L and DA series.

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07-16-2014, 03:05 PM   #4
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No. Only the F, FA and DA lenses have the capacity to autofocus. Older lenses (M, K and the M42 glass) have to be manually focused (as we all had to in the old days). It is not much of an issue in many situations and gets you relatively inexpensive access to some great lenses. There is a good article here by Adam on "How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-5, K-r, K-x, K-7...)".

07-16-2014, 03:42 PM   #5
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Unless you have a Pentax auto-focus adaptor, in which case the manuals will autofocus (well strictly the adaptor focusses it).

AFA Review
07-16-2014, 05:28 PM   #6
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QuoteOriginally posted by SteveUK Quote
Unless you have a Pentax auto-focus adaptor, in which case the manuals will autofocus (well strictly the adaptor focusses it).

AFA Review
Now if only Pentax would start selling that sort of stuff again...(DA AFA 1.2x would be nice, haha)
07-16-2014, 06:10 PM   #7
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QuoteOriginally posted by stevebrot Quote
When using manual focus, you still have the option of focus confirmation. The AF system will signal when it has determined that focus has been attained. Focus confirmation is limited to the center spot focus sensor.


Steve
Steve is correct of course, but I see "Catch in Focus" as a tool that allows me to cheat a bit. You set it, press the release and focus until the picture is taken. Just thought I'd add that as it wasn't mentioned earlier.

07-16-2014, 09:43 PM   #8
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The perfect new optical offering from Pentax would be a 0.65x autofocus adapter, so you could use your M 28/2.8 as an autofocusing 28mm lens on a K-5 or K-3.
07-17-2014, 12:57 AM   #9
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QuoteOriginally posted by bkpix Quote
The perfect new optical offering from Pentax would be a 0.65x autofocus adapter, so you could use your M 28/2.8 as an autofocusing 28mm lens on a K-5 or K-3.
A full frame adapter! Thats ingenious!

Seb
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