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12-22-2011, 09:04 AM   #1
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Trouble with SMC-A lenses?

I have been considering upgrading my K20 to a K5. I own and use 4 1980's vintage Pentax manual focus lenses with an "A" setting that work just fine for me, but I have heard of several K5 owners having trouble with these lenses working properly: basically they won't stop down but remain at full aperture as if they were a "M" lens. Did Pentax change the settings for older manual focus lenses on the K5 that would cause problems? If so, what do you have to do differently from my K20?

12-22-2011, 09:31 AM   #2
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'A' lenses should work just fine with the K-5, the only difference to more modern lenses are them being MF and that one needs to enter the FL on power-up for SR to work properly as the lenses do not communicate their FL to the body. Beacause of the latter 'A'-zooms would be more inconvenient and/or it can be said that SR is not as useful with them as with the more modern ones for which the body 'knows' the FL.
12-22-2011, 09:48 AM   #3
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These lenses stay at full aperture only if they are not put in "A" setting and the body is in Av mod.
12-22-2011, 09:49 AM   #4
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QuoteOriginally posted by jeverettfine Quote
heard of several K5 owners having trouble with these lenses working properly:
As jolepp states, 'A' lenses just work. You will need to focus manually, of course, and the shake reduction function will ask you what the focal length is because 'A' lenses do not report that. I believe the 'F' series was the first to report focal length.

Can you show a reference to k-5 owners having trouble using 'A' lenses? This is the first I have heard of any issues whatsoever with the 'A' series. Unless they do not have the lens in the 'A' position, in which case it will function the same as an 'M' or 'K' series.

Here is an article on using 'M' & 'K' lenses: how-use-meter-manual-m42-lenses-all-pentax-dslrs-k-5-k-r-k-x-k-7

12-22-2011, 09:58 AM   #5
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They will operate on the K5 exactly as they do on the K20D. Exactly, no different, just the same, etc. As suggested, the only problems occur to those who haven't used A-type lenses before. You *have* used them on your K20D, so no problem. Upgrade with confidence.
12-22-2011, 05:40 PM   #6
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I just put my A50/F2 on the K-5, stopped down to f/22 using the back dial - in Av exposure mode.
Took a shot - 2s shutter speed.
Then changed to f/6.3 and took another shot - shutter speed of the 2nd taken shot was 1/8s.

So as long as you leave the aperture ring in the "A" position, the camera is definitely controlling the lens aperture.

12-23-2011, 06:56 AM   #7
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I would imagine the problem, if it exists at all, comes from third party lenses that don't short the data pin. It's possible the K5 handles this differently from the K20. (I know it refuses to stop down lenses with (fully) insulated mounts, and the K20 didn't.)

Pentax lenses should be fine, and it's trivial to fix any lens with this problem anyway. (Just some conductive paint.)
12-23-2011, 08:34 AM   #8
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The aperture control lever can get bent, not allowing the body to control. More of an issue with longer lenses where the weight can cause damage. Easy to test the whole thing, in A settings, set your aperture smaller on the body and either hit the green button or twist the power button to preview. You should see a darkening of the viewfinder if the aperture mechanism is working fine.

12-23-2011, 06:33 PM   #9
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I have several KA lenses and they all work fine. I used them on my IST ds and now my K5. I also have a defective KA lens that is missing the little pin that talks to the camera. (I lost it while servicing the lens.) It still works, but only when you meter via the green button.

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