Having problem with FD lens and adapter - help!

When mounting and unmounting FD lenses, the adapter should be set to the "Open" position (counterclockwise when looking into the front element of the lens).

If you mounted the lens while the adapter was in "Lock", you may have mashed the adapter's aperture release pin with the aperture lever of the lens. That may in turn be putting pressure on the nFD style bayonet. You may need to apply quite a bit of torque to get the lens back off. If/when you do, see whether the pin in the adapter is bent. If it is, you can probably straighten it and try again.

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Nex-7 with kit lenses, Contax G 35, and a number of legacy lenses (mostly Canon FD)