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10-20-2014, 08:25 AM   #1
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Aperture stuck at 1.7 unless loosened off.

Hi all,

I recently purchased an old second hand SMC 50mm 1.7 (k mount). It's an all manual jobby.

There's a problem however. When I attach it to my K-3 body the aperture opens up to f/1.7 and stays there. The aperture ring moves through all positions, but the aperture blades themselves remain wide open. If I loosen the lens about half an inch from its locking position then all f stops work fine and the lens does its job. But this irritates me, and I'd like to remedy it if possible. Does anybody know why this is happening, and more importantly, how to rectify it?

Thanks in advance.

p.s. It's not possible to get refunded.


Last edited by Noc; 10-20-2014 at 08:32 AM.
10-20-2014, 08:41 AM   #2
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This could be appropriate behavior... the camera will stop down as soon as you press the shutter.

Does DOF stopping-down work? I don't have an SMC level lens to check it out on, but my older manual lenses still have the aperture lever, and I thought the SMC's had it too, but I don't know for sure.

If you want to have the camera perma-DOF... dunno if it's possible on the K-3.
10-20-2014, 08:48 AM   #3
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Press the Green Button and see what happens.
10-20-2014, 08:52 AM   #4
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This lens is working in open metering mode. It will close down to preselected value when you take your photo., First set camera to M mode and make sure your ISO is set to fixed valuye (e.g. 100, 200 , etc. ) - you can use green button as suggested to meter the exposure. I suggest you do little research on how to use your camera - because you will quickly run into some problems without basic knowledge .

10-20-2014, 08:52 AM   #5
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QuoteOriginally posted by ElJamoquio Quote
This could be appropriate behavior... the camera will stop down as soon as you press the shutter.

Does DOF stopping-down work? I don't have an SMC level lens to check it out on, but my older manual lenses still have the aperture lever, and I thought the SMC's had it too, but I don't know for sure.

If you want to have the camera perma-DOF... dunno if it's possible on the K-3.
No, when properly locked onto the body (turned to the click) the lens does not stop down, it remains wide open. I ran off a series of shots at each stop and realised the DOF was exactly the same in each one - which is how I discovered the problem.

All of my lenses have the aperture lever, but I've noticed on the 50mm 1.7 it is the widest lever of them all. Perhaps it could be this?
10-20-2014, 08:53 AM   #6
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Read my advice above
10-20-2014, 08:54 AM   #7
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QuoteOriginally posted by Noc Quote
No, when properly locked onto the body (turned to the click) the lens does not stop down, it remains wide open. I ran off a series of shots at each stop and realised the DOF was exactly the same in each one - which is how I discovered the problem.

All of my lenses have the aperture lever, but I've noticed on the 50mm 1.7 it is the widest lever of them all. Perhaps it could be this?

Ah. So when you try to stop down on DOF mode, it doesn't work, either? What if you fiddle with it by hand, does it feel 'sticky'?

If it has the lever, it should be working appropriately... there's no reports of any SMC lenses not working on the K-3.
10-20-2014, 09:06 AM   #8
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QuoteOriginally posted by manntax Quote
This lens is working in open metering mode. It will close down to preselected value when you take your photo., First set camera to M mode and make sure your ISO is set to fixed valuye (e.g. 100, 200 , etc. ) - you can use green button as suggested to meter the exposure. I suggest you do little research on how to use your camera - because you will quickly run into some problems without basic knowledge .
You've saved the day, thank you. I do understand the basics and have had no problems at all until now. But I'm very embarrassed to admit that I overlooked the obvious with this one. You live and learn.

10-20-2014, 09:23 AM   #9
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Also check that you have the "Allow aperture ring" or somesuch in the custom menu set to 2 (allow).
10-20-2014, 10:46 AM   #10
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Common mistake, the camera does not close the aperture blades the lens spring does. The camera just holds them open and drops it's
lever to a predetermined position based on the value selected.That is why sticky blades can cause over exposure and some manual lenses
not to expose properly if the linkage is not linear for digital.
10-20-2014, 11:45 AM   #11
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QuoteOriginally posted by LensBeginner Quote
Also check that you have the "Allow aperture ring" or somesuch in the custom menu set to 2 (allow).
+1 - this should be your first step. Then put the camera in manual. set aperture on lens. press green button to meter. take picture and be wowed.
10-20-2014, 01:44 PM   #12
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Thanks for the advice. I set the aperture ring setting way back when I first attached a manual lens. It was not pushing the green button that caused my current problem. It's sorted now, and yes, I am really wowed. For the lowly price I paid I'm struck at how sharp it is.
10-20-2014, 01:50 PM   #13
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QuoteOriginally posted by Noc Quote
Thanks for the advice. I set the aperture ring setting way back when I first attached a manual lens. It was not pushing the green button that caused my current problem. It's sorted now, and yes, I am really wowed. For the lowly price I paid I'm struck at how sharp it is.
Hehe... I should know... I have it too (hell, most of us have it too, I guess)!
At f/5.6 it really is a knife's edge...
10-20-2014, 02:20 PM   #14
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A K-3? You should be able to set the DOF preview to optical so you can use stop-down metering with the exposure bars active in Manual mode. Set to Manual mode, turn on the meter (half press), operate the DOF preview. The lens should stop down to the aperture set on the ring. Use the ring to change aperture and the eDial for the shutter speed the exposure bars should show the EV.
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