Aperture stuck in stopped-down position after exposure - Samyang 85mm

Started Oct 6, 2009 | Discussions thread
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Akeem
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Aperture stuck in stopped-down position after exposure - Samyang 85mm
Oct 6, 2009

I have used the Samyang 85mm f/1.4 for Pentax since June 2009 but in the last few weeks it has developed a problem.

The aperture gets stuck in the stopped-down position after making an exposure. This happens most of the time.

The aperture is in position "A" so it should return to wide open after the exposure. A slight tap, focus-change or change in aperture gets the aperture "unstuck". But if I do nothing the viewfinder remains dark after an exposure. I noticed that IF the aperture returns to wide-open this happens rather slow: 0.5sec instead of instantaneous.

I use the lens on a Pentax K10D. No other lens exhibits a similar problem.

Is there a form of lens maintenance or mechanical correction to the aperture coupling of the K-mount I should execute to get the aperture to loosen up?

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