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01-12-2008, 12:41 PM   #1
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Lens Problem

Hello,

I've noticed a problem with one of my lenses and would appreciate any help from forum members.

I have a smc-pentax-m 200mm f4 which I have been using manually on my Ist DL using stop down metering. All works fine from f32 down to even f4. But once I hit f4 and try going back up to f8 or f11 (for example), the aperture may be set to f8, but I'm finding it's physically still set wide open.

In short,
when pressing the AE-L button in manual mode with aperture ring permitted,

Starting from f32 all the way down to f4, I can see the viefinder brightening up as I open up.
The blades are working properly, metering is accurate.

Starting from wide open, f4, then try going back the other way(f5.6,f8, f11 ..) the aperture ring moves but the aperture blades do not. They remain wide open. Whatever aperture I use now, it now doesn't matter as I'm now stuck wide open.

When the lens is not attached to the camera, I can see the blades open and close up while I move the aperture ring. It is only when I attach the lens to the camera where I find that the blades will open without any problem, but will NOT close.

Any recommendations on how to solve this problem I'm having with this lens would be greatly appreciated.

Thank You.

01-12-2008, 01:05 PM   #2
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QuoteOriginally posted by kplik Quote
Hello,

I've noticed a problem with one of my lenses and would appreciate any help from forum members.

I have a smc-pentax-m 200mm f4 which I have been using manually on my Ist DL using stop down metering. All works fine from f32 down to even f4. But once I hit f4 and try going back up to f8 or f11 (for example), the aperture may be set to f8, but I'm finding it's physically still set wide open.

In short,
when pressing the AE-L button in manual mode with aperture ring permitted,

Starting from f32 all the way down to f4, I can see the viefinder brightening up as I open up.
The blades are working properly, metering is accurate.

Starting from wide open, f4, then try going back the other way(f5.6,f8, f11 ..) the aperture ring moves but the aperture blades do not. They remain wide open. Whatever aperture I use now, it now doesn't matter as I'm now stuck wide open.

When the lens is not attached to the camera, I can see the blades open and close up while I move the aperture ring. It is only when I attach the lens to the camera where I find that the blades will open without any problem, but will NOT close.

Any recommendations on how to solve this problem I'm having with this lens would be greatly appreciated.

Thank You.
The answer depends on your camera model to a certain extent.

On the K10D, for example, after changing the f/stop on the ring, (with the enabled setting, of course), using the stop down depth of field preview (mechanical mode only - not the LCD preview!) will show you the metering, and the lens will operate as expected, with wide open focus viewing, and stopped down to the correct aperture when shooting.
01-12-2008, 02:02 PM   #3
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If the lens has problem only when attached to the body, sounds like the lever sticking out at the rear of the lens was stuck with the body at f4. Try to push it inward "slightly" (less than 1mm) and see if the problem goes away.
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