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03-03-2012, 02:39 PM   #16
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Lowell Goudge's Avatar

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Go back to the beginning.

With no A contacts, the camera does not know maximum and minimum aperture. As a result in Av mode the camera always holds the aperture open regardless of the aperture ring setting. As a result all shots are metered wide open and shot wide open in Av mode

In manual mode, the green button function stops the lens down to the selected aperture and meters (sets shutter speed) to match the aperture when stopped down, then when you shoot the camera lets the lens stop down.

In many ways, M42 lenses are easier to use because you manually stop the lens down and the viewfinder darkens, but in Av mode at least the camera meters for the stopped down position.

It is not really a big issue, you don't need to meter evy shot. I simply meter off something mid grey in the scene with spot metering with the same lighting as the subject, and let the camera pick the shutter speed, then until lighting changes you have correct exposure

03-03-2012, 03:55 PM   #17
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I wouldn't go disfiguring any M lenses by removing their aperture levers. That it has one is a feature. Having the viewfinder darken makes focusing much more difficult. This is why they started making M lenses in the first place. The camera uses that aperture arm to hold the diaphragm wide open so you can focus, and it releases it when you shoot, so that it closes to the aperture selected on the lens. Manual mode and green button are by far the best way to do this on a DSLR. I'd suggest you forget about using Av with these lenses.
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