@engardeknave
"Dude. They are using the M42 adapter as a new mount."
"It also seems unlikely to me that the conversion in the video is going to result in a lens that focuses precisely to infinity without any change in the length of the lens. There are some other adapters they could be using that may vary in width by a half-millimeter or so, which would affect focus."
My conversion kit are not the M42 mounts. The conversion plate used in my kits was designed specifically to convert the FDn lenses into native Ef mounts while maintaining the camera bodies original crop factor while achieving infinity focus. There are two of us that have taken this approach toward converting FD lenses; designing from scratch; to achieve the best possible alignment, matching the original mount design. These parts are CNC machine to +/- .001 on equipment that can maintain +/- .0001 or tighter. The bottom of the conversion plate is designed to self center on the lenses to maintain the correct axial alignment as well. This is something you will not get by using a modified M42 mount.
"Dude. They are using the M42 adapter as a new mount."
"It also seems unlikely to me that the conversion in the video is going to result in a lens that focuses precisely to infinity without any change in the length of the lens. There are some other adapters they could be using that may vary in width by a half-millimeter or so, which would affect focus."
My conversion kit are not the M42 mounts. The conversion plate used in my kits was designed specifically to convert the FDn lenses into native Ef mounts while maintaining the camera bodies original crop factor while achieving infinity focus. There are two of us that have taken this approach toward converting FD lenses; designing from scratch; to achieve the best possible alignment, matching the original mount design. These parts are CNC machine to +/- .001 on equipment that can maintain +/- .0001 or tighter. The bottom of the conversion plate is designed to self center on the lenses to maintain the correct axial alignment as well. This is something you will not get by using a modified M42 mount.