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10-27-2009, 07:44 AM   #1
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Metering trouble with Sigma 70-300 and K2000

I am hoping some of you more experienced fellows will be able to help me with this problem, or at least maybe find someone who has had a similar experience. I recently bought a Sigma 70-300 APO DG lens, new, and for two weeks it worked flawlessly. Then, last weekend, the dang thing stopped metering properly. After extensive test shots and stifled cursing, I have narrowed it down to the strange symptom of the camera not controlling the aperture in auto. Regardless of what settings I put in on (in camera), it basically stays at f/4. The camera and exif data read f/whatever I put, but anything over f/4 and it begins to overexpose. I have tried another lens with an aperture ring, as well as my kit lenses, and they all work just fine, which leads me to believe that it's the Sigma. I wish I had another body to try it on, but for now I don't. I might try going over to Sam's Club to see if they will let me "test drive" the K20D with it, if so I will update. Anyone have this happen to them? With any lens at all?

Thanks for the help!

10-27-2009, 07:50 AM   #2
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With lens off camera.
Set aperture ring to F22. See if the blades close up. Then see if the lever at the back of the lens will open the blades.
10-27-2009, 08:29 AM   #3
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Yes to both. After more test shots and comparisons with my Pentax 50-200, here is more info. At 70mm and f/22, the camera meters the shot on both lenses at 1.5" (in my not so well lit office). Pentax exposes just right, Sigma it's almost completely white. It seems that the aperture is not truly stopping down to f/22. Even in manual mode, with aperture ring at f/22 and shutter speed at 1.5", it's overexposed to the point of nearly white in whole frame. I am heading to Sam's club to test drive the K20D (wanted an excuse to do that anyway).
10-27-2009, 08:49 AM   #4
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Sounds like the mechanical connection between camera and lens isn't working. By chance is the lens lever bent in toward the rear element at all? It doesn't take much to keep the two levers from connecting.

10-27-2009, 09:52 AM   #5
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QuoteOriginally posted by veegish Quote
Even in manual mode, with aperture ring at f/22 and shutter speed at 1.5", it's overexposed to the point of nearly white in whole frame. I am heading to Sam's club to test drive the K20D (wanted an excuse to do that anyway).
I seriously doubt it's a camera issue then. You say the lever moves the blades, but is the movement quick and snappy? If not, there's your problem. And as the last poster noted, check the mechanical connection between the two.
10-27-2009, 10:21 AM   #6
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Doesn't look bent, here's a photo of the Sigma compared to my Pentax-A 50 f/2. Action on the Sigma is snappy. The only discrepancy I can even guess at is that the 50mm's lever is a little further to the right side of the opening when in "A" mode than the Sigma's is...
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10-27-2009, 12:30 PM   #7
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The arrow ponits to the uneven gap. The lever does not look like it is parallel to the slot sides. If it is slightly off angle, the camera's lever will not connect allowing the change of aperture.

Last edited by wildlifephotog; 09-27-2013 at 07:22 AM.
10-27-2009, 02:09 PM   #8
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That is what I thought, it's going back to Sigma today...

Thanks all!

10-27-2009, 06:15 PM   #9
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QuoteOriginally posted by wildlifephotog Quote
The arrow ponits to the uneven gap. The lever does not look like it is parallel to the slot sides. If it is slightly off angle, the camera's lever will not connect allowing the change of aperture.
Actually, mine has the same gap, and works fine. However mine does seem to be a hair longer than the OP's.
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