Originally posted by hahifuheho a 50mm f/1.4 M42 Super Takumar with my K200D in the Av mode
Does any one knows why this might be happening?
I've not got a K200D, but I guess it is similar to the K100D in this respect. In Av there will be metering errors. Different lenses have different errors, and the errors vary with the aperture used. However, the camera will meter correctly in M when using the green button (on the K100D that is the AE-L button).
However, there is a workaround. If you short the camera contacts with a piece of Aluminium foil between the lens and camera mount the camera will meter correctly. I have tried this with my Karl Zeiss lenses and my Takumars and it works. However, if you regularly change lenses it can be tedious since the foil gets ripped. I've used shims - the metal that you get in shop security tags is suitable - but they are easy to lose (and before now I've cut my thumb on the corner of the shim when focusing, so I always cut off the corners). Consequently, I usually just use M mode and the green button, it's much easier.
(The only time when the short-the-contacts trick is essential is when you want to do "focus trap". In this case the camera is in AF mode, you depress the shutter and turn the focus ring and when something comes into focus the camera takes a shot - a kind of poor man's AF with MF lenses! This does require the contact shorting.)
Richard