Pentax M 50mm 1.7 Shutter Issue

lotus · 09-04-2019, 08:22 PM

I have a pentax K-30 and recently just got a pentax-m 50mm 1.7. The lens seems to be in good condition, but whenever I attach it to my camera the shutter starts going off randomly every few seconds without me doing anything. When I try to take a picture the shutter goes off twice in quick succession giving me a completely blurry picture. This happens no matter what my aperture is set to. All my other manual and auto lens seem to work fine without any problems. Anyone have experience with this and can help please?

stevebrot · 09-04-2019, 10:07 PM - **2 Likes**

Welcome to the Pentax Forums!

Does the aperture actuator on the lens work? Take the lens off the camera and with the aperture ring in the at f/22 (lens should appear fully stopped down), flick the lever on the back. The iris should quickly open and close without hesitation or sticking or significant resistance.

Is the aperture lever in good condition and similar in appearance to your other lenses? Specifically is it bent, scarred, cut, or mangled in any way that might allow it to improperly mate to the coupling in the mirror box?* If so, do not mount the lens back to your camera. I suspect that it may be slipping past the coupler in the mirror box and jamming the mechanism to cause something similar to what has been called mirror flop. This would not be a good thing. To be honest, I don't think I would mount it to a camera, regardless of appearance, unless it has been evaluated by a competent lens repair tech.

Steve

* It is not real obvious, but when the lens is mounted, the actuator is supposed to engage the underside of the coupler as the lens is rotated on such that the iris diaphragm opens fully. During exposure and at certain other times, the coupler moves upward to allow the lens to stop down.

lotus · 09-05-2019, 02:53 PM - **2 Likes**

Thank you so much for your response! You were right! The aperture lever was working fine when I flicked the lever and looked fine, but when I compared it to my other lens there was the slightest little inward bend that I guess was causing problems or slipping when mounted on the camera. I straightened it a bit and now everything seems like it's working fine. Thank you again!

stevebrot · 09-05-2019, 07:29 PM

Originally posted by lotus

Thank you so much for your response!

That's how we roll here! My pleasure.

Steve

09-04-2019, 08:22 PM	#1
lotus New Member Join Date: Sep 2019 Posts: 2	Pentax M 50mm 1.7 Shutter Issue I have a pentax K-30 and recently just got a pentax-m 50mm 1.7. The lens seems to be in good condition, but whenever I attach it to my camera the shutter starts going off randomly every few seconds without me doing anything. When I try to take a picture the shutter goes off twice in quick succession giving me a completely blurry picture. This happens no matter what my aperture is set to. All my other manual and auto lens seem to work fine without any problems. Anyone have experience with this and can help please?

09-04-2019, 10:07 PM - 2 Likes	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Welcome to the Pentax Forums! Does the aperture actuator on the lens work? Take the lens off the camera and with the aperture ring in the at f/22 (lens should appear fully stopped down), flick the lever on the back. The iris should quickly open and close without hesitation or sticking or significant resistance. Is the aperture lever in good condition and similar in appearance to your other lenses? Specifically is it bent, scarred, cut, or mangled in any way that might allow it to improperly mate to the coupling in the mirror box?* If so, do not mount the lens back to your camera. I suspect that it may be slipping past the coupler in the mirror box and jamming the mechanism to cause something similar to what has been called mirror flop. This would not be a good thing. To be honest, I don't think I would mount it to a camera, regardless of appearance, unless it has been evaluated by a competent lens repair tech. Steve * It is not real obvious, but when the lens is mounted, the actuator is supposed to engage the underside of the coupler as the lens is rotated on such that the iris diaphragm opens fully. During exposure and at certain other times, the coupler moves upward to allow the lens to stop down. Last edited by stevebrot; 09-04-2019 at 10:45 PM.

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09-05-2019, 02:53 PM - 2 Likes	#3
lotus New Member Join Date: Sep 2019 Posts: 2 Original Poster	Thank you so much for your response! You were right! The aperture lever was working fine when I flicked the lever and looked fine, but when I compared it to my other lens there was the slightest little inward bend that I guess was causing problems or slipping when mounted on the camera. I straightened it a bit and now everything seems like it's working fine. Thank you again!

09-05-2019, 07:29 PM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by lotus Thank you so much for your response! That's how we roll here! My pleasure. Steve