Originally posted by stevebrot Define "infinity"...
Many vintage lenses were adjusted at the factory to an arbitrary standard based on focal length (e.g. 2000x or similar). Such works fine with optical viewfinders,* but not so well when using 1:1 magnification in digital live view. Most lenses allow for adjustment of infinity focus and with some it is as easy as shifting the focus dial a few degrees. On others, some disassembly may be required.
Steve
* Consider degrees of arc for a 28mm lens along with average visual acuity and very quickly, 60m and the horizon start to look pretty much the same in the viewfinder, even for a sensitive split-image focus aide. Several of my 28mm lenses dial in at about that distance.
I have a wonderful Orion-15 6/28 lens in Soviet rangefinder M39 mount. Many copies of it are reported as being unable to achieve "infinity" focus on adapted mirrorless platforms, and it isn't easily adjustable without shaving down the hard stop pins inside. Mine is exactly the same. I thought about shaving the pins, but for the sake of originality, I just live with it. The result is, distant detail isn't quite as defined as it otherwise could be, especially when viewing images at 1:1 reproduction on my displays. At some point, I'll shave an L39 adapter specifically for that lens...