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12-31-2013, 08:15 AM   #1
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645N acting up

I used the 645N this morning and it was acting strangely. I was shooting in aperture priority mode with shutter speed dial set to A. Regardless of which lens I attached, stopping down the lens didn't get recognized by the display in the viewfinder. The display always showed the lens to be wide open and the shutter speeds selected by the camera were based on the mistaken aperture value. But if I had the lens stopped down the aperture blades did close down when the shutter was released. So I was able to meter with my DSLR and shoot in manual mode.

Now here's the weird part. With the shutter speed dial set to A, no matter what I did with the aperture ring on the lens, the viewfinder always indicated that the lens was wide open. But when I put the camera in full auto mode by turning the lens aperture ring to A as well, then the viewfinder would display aperture values other than wide open and correspondingly correct shutter speeds.

Does anyone have any idea what was going on? Unless I was making some sort of really basic mistake, I think the camera may need some sort of repair, so I'll probably be taking it in soon. The weather was very cold when I was shooting but I tested it out again after getting home and bringing the camera into the house and it did the same thing.

12-31-2013, 08:52 AM   #2
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I do not think you make a mistake, and I cannot replicate it on my 645N. Would cleaning the contacts between body and lens help?
01-01-2014, 04:57 AM   #3
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I cleaned the contacts but no change. Then I looked carefully in the camera with the lens removed and noticed that the lever near the bottom of the mount, which moves as aperture ring is adjusted was stuck at one end. When I pushed it with my finger it returned to the other side, as if the spring was weak or something. After that the camera has returned to normal function. Actually, not quite normal but almost. The lever is still a bit sticky so as I stop down the lens the numbers in the viewfinder sometimes stop at f/9 or f/11 even though the lens is set to f/22. But at least I now know the cause and will take it in for adjustments. Probably just needs some lubrication or something.

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