*istD overexposure with manual lenses

[Peter Smekal]

Hi folks,
I was trying out some of my K and M lenses on the *istD: 24/2.8, M28/2.8,
35/2.8, M50/1.4, M85/2. I was really looking forward to use some of these
old pearls. The strange thing is that I get very overexposed pictures with
the M50/1.4 and the M28/2.8. I am using the M mode + the green button.
Firmware is updated. Any explanation?
Peter