It may be that any adapter to go from an M-42 lens to the Minolta SR mount will require some glass in the optical path to achieve focus at infinity. Both of the Minolta Adapters for the M-42/Contax/Pentax/UTM lenses and the Leica M-39 lenses are simple machined adapter rings without any glass, and specifically state in the instructions that they are for use in close-up work only, and will not achieve focus at infinity.
The lens registration distance for the Minolta Maxxum/Dynax AF lens mount and the later Sony DSLR AF lens mount is longer than the Minolta SR lens mount, so the same comments will apply there also.
Hmmmmm nope, both the Minolta SR and AF mounts focus to infinity with plain non-glass adapters. I use a large number of Pentax Takumar lenses with both and have no issues.
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