Mamiya 645 AFD & Valeo and over exposure

[BigWooha]

Hi all

Hope somone out there can help me with this before I go nuts.

I was using my 645 AFD with a Leaf Valeo 22wi back and tried using a 150mm 3.5N manual lens for some head shots. The strobes were being triggered by a set of Bowens Pulsars attached to the 645 hotshoe

With the apeture ring manually stopped down to match my light meter off I went, only to see nasty over exposed shots.  

I tried switching the A.M lever on the lens from A to M (which I belive is only for DOF preview) and hey presto slightly under exposed but pretty close.

I switched over to my 80mm AF lens and all was well. So I'm pretty confident it's something to do with the lens or me being stupid.

I'm still getting to grips with this kit can anyone explain why it would be overexposed when set to A?

Thanks
G

[amsp]

The switch needs to be on M, then you have to manually stop down the aperture. There is no auto-aperture using the old lenses on an AFD.

[BigWooha]

I thought that might be the case, thanks for the help