Confused by OM 50mm lenses

Don't forget, a proper lens hood in daylight can make a tremendous difference.

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Just as a follow up, I have continued looking for a sharp 50mm...the Pentax M 50/1.4, contrary to popular opinion, is sharper by my testing than the 50/1.7, which in turn was sharper than the Oly MIJ 50/1.8. The M 50/1.4 hit its peak at f4, ie, it was diffraction limited by f5.6. In contrast, pun intended, the MIJ didn't hit its peak contrast/resolution until f8.

Doesn't do a bit of good if it doesn't mount on an OM-1

There were five different mechanical versions of the /1.8 OM 5cm.