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02-04-2009, 10:46 AM   #1
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Uh, oh. SMC-A and lens contacts?

All right, this one's weird. I've just received an SMC_A 28 2.8, and the camera will not recognize the focal length, also, seems to be recording exposure info of like one to six seconds in daylight, (though the quick test exposures I've done exposures are more or less proper.) I don't seem to be getting good focus, either, so this may be a wash, anyhow, (maybe adjustment's required. )

I was given to believe A lenses would operate normally on the K20d. Any ideas what gives, here?

Addendum: it seems the actual exposure info comes out in playback mode, but when I chimp and hit the info button, unless in manual or Tv mode I get these wildly-long exposures cited.


Last edited by Ratmagiclady; 02-04-2009 at 10:58 AM. Reason: More info.
02-04-2009, 10:58 AM   #2
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The A lens doesn't have a chip, so the camera has nothing to recognize. Input focal length manually when the camera asks for it on startup. You will not have FL available in EXIF though. (Atleast not that I've been able to make happen).

Try cleaning the contacts, I use a pencil eraser and rub then gently. It doesn't take much effort to clean them.
Regarding focus, I am going to presume that you've checked the obvious, like your diopter correction and that you've inspected the lens carefully. If this is your first manual focus lens, it's possible that your focus screen isn't quite shimmed in correctly and you haven't noticed before.
02-04-2009, 11:14 AM   #3
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QuoteOriginally posted by Wheatfield Quote
The A lens doesn't have a chip, so the camera has nothing to recognize. Input focal length manually when the camera asks for it on startup. You will not have FL available in EXIF though. (Atleast not that I've been able to make happen).

Try cleaning the contacts, I use a pencil eraser and rub then gently. It doesn't take much effort to clean them.
Regarding focus, I am going to presume that you've checked the obvious, like your diopter correction and that you've inspected the lens carefully. If this is your first manual focus lens, it's possible that your focus screen isn't quite shimmed in correctly and you haven't noticed before.
Ah. I'd thought the configuration of contacts told the camera what focal length. That answers that much. I don't understand why the chimping info should be claiming these wild shutter speeds, though.

I'm in the process of inspecting this lens as we speak, actually: the seemingly-bizarre behavior seemed to mean possibly I should just stop there and return it.

It's not the first manual focus lens I've put on here, but in some ways it may as well be. (I snagged an M 'takumar bayonet,' a 135, but haven't gotten to playing with it too much, my health's been so-so at best most of the time I've had this camera, actually, so I've been waiting for better eyesight and concentration days to set up and do any fine-tuning of focus. And in the case of that 135, waiting for steadier hands. )

I really hope the focus screen isn't out of alignment: I've had my suspicions, but haven't been able to really settle in and figure this out or see if there may be simple front-or-back-focus issues and how to save the lens info.

The contacts do seem to be clean, I've given them a quick going over. I suppose I should be more thorough for the sake of any troubleshooting process.
02-04-2009, 11:21 AM   #4
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Make sure you have the lens set to A?

02-04-2009, 11:24 AM   #5
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QuoteOriginally posted by Wheatfield Quote
The A lens doesn't have a chip, so the camera has nothing to recognize. Input focal length manually when the camera asks for it on startup. You will not have FL available in EXIF though. (Atleast not that I've been able to make happen).
I just checked a PEF I took with my A 50 f/2 in PhotoMe and it actually shows under lens data "smc PENTAX-A 50mm F2." I had thought for sure that inputing the focal length would make the FL show up in EXIF but I just noticed that the full lens name came up in EXIF. Maybe you are refering to the M lenses?
02-04-2009, 11:29 AM   #6
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No, it's an A lens with the aperture ring set to A. Really.
02-04-2009, 11:33 AM   #7
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OK. So, it seems I'm not getting sharpness on distant objects with the lens at infinity. Is this something that means front or back focusing adjustments could help?
02-04-2009, 11:35 AM   #8
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QuoteOriginally posted by MrApollinax Quote
I just checked a PEF I took with my A 50 f/2 in PhotoMe and it actually shows under lens data "smc PENTAX-A 50mm F2." I had thought for sure that inputing the focal length would make the FL show up in EXIF but I just noticed that the full lens name came up in EXIF. Maybe you are refering to the M lenses?
Oh. Would this mean an A lens would be supposed to be recognized?

02-04-2009, 11:46 AM   #9
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I would say yes. Any "A" lens should work correctly on any Pentax K mount body. My 50 f/2 worked and metered fine when mounted on my K100DS.
02-04-2009, 11:52 AM   #10
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QuoteOriginally posted by MrApollinax Quote
I would say yes. Any "A" lens should work correctly on any Pentax K mount body. My 50 f/2 worked and metered fine when mounted on my K100DS.
Eh, now I'm just confused. Whatever happened to 'things working?'
02-04-2009, 11:54 AM   #11
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QuoteOriginally posted by MrApollinax Quote
I just checked a PEF I took with my A 50 f/2 in PhotoMe and it actually shows under lens data "smc PENTAX-A 50mm F2." I had thought for sure that inputing the focal length would make the FL show up in EXIF but I just noticed that the full lens name came up in EXIF. Maybe you are refering to the M lenses?
Interesting. I just checked and Photo ME is giving me the same sort of results, I've never gone through the data that thoroughly before with this program. I also figured that inputting FL to the shake reduction would have an effect on the focal length, but I was certain that A series lenses predated the type of lens field data that came with the later AF lenses.
Another day, and I've learned something new.
This is good.
02-04-2009, 11:58 AM   #12
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QuoteOriginally posted by Wheatfield Quote
Interesting. I just checked and Photo ME is giving me the same sort of results, I've never gone through the data that thoroughly before with this program. I also figured that inputting FL to the shake reduction would have an effect on the focal length, but I was certain that A series lenses predated the type of lens field data that came with the later AF lenses.
Another day, and I've learned something new.
This is good.
So... The thing about not seeing the focal length in camera is still normal behavior?
02-04-2009, 12:07 PM   #13
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I think I remember that you'll see focal length info with SR turned on, but it won't be stored if SR's off. I'll try to remember to check later and report back...
02-04-2009, 12:19 PM   #14
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QuoteOriginally posted by heliphoto Quote
I think I remember that you'll see focal length info with SR turned on, but it won't be stored if SR's off. I'll try to remember to check later and report back...
Info from where of what?


With what?

If Wheatfield was right and the focal length info must come from a chip, perhaps if the camera gets info on aperture and maximum aperture, but no chipped identification, the computer simply assumes it's an A lens of some kind, and gives you the info from the focal length you input?

I'm now confused on the point of whether the camera should be reading an A lens's focal length in-camera, if you don't set it yourself. Anyone?


Sorry if I sound testy.
02-04-2009, 12:30 PM   #15
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QuoteOriginally posted by Ratmagiclady Quote
Info from where of what?


I'm now confused on the point of whether the camera should be reading an A lens's focal length in-camera, if you don't set it yourself. Anyone?
As far as I know, A-Lenses only report aperture. Not focal length. I generally use SR (Shake Reduction) which requires you to input your focal length. If you input your focal length, then it will be reported properly in the EXIF information.

At least this is true on my K100D. The general limitations are that you have to power cycle (the fastest way to set a new SR length) to switch lenses, and you have to round focal length to the nearest value in SR. There is another way to set SR length, but it is buried deep within the menus so I never bother.

I will have to go back and check my A-lenses when I get home, but I think this is generally the case.

-southy
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