Upload & Sell: On
Hm, yeah. The old 50/1.4 uses the really crappy first-generation focus-position-encoder. It's not really a good tool to judge camera shot-shot variation on...
Even the APS kit-lenses Canon makes now uses a lot higher res encoders. Like about three times more accurate focus positioning. :-)
At least one of us (that would be me) would absolutely kill to get some more information about focus encoders and encoding systems.
I know Nikons are generally magnetic and Canon's optical, but that's the extent of my knowledge (other than a thorough working knowledge of how to ruin them during lens disassembly).