I had a big old Omega enlarger, gotten from some junk pile, with only half its condensers, and for a lark I took the top off, and left the one condenser lens in place, and fitted the lens board with a Nikon mount made from an old T adapter. The result was a surprisingly amusing monster lens. A rough estimate was that it was about a 200 mm F 2+ singlet capable of macro focusing. The chromatic aberration was surreal, but it actually became tolerably sharp when stopped down (with construction paper waterhouse stops). I gave it to one of my kids to mess with, and haven't used it since I started doing digital photos, so I haven't got much to show, but if you are stuck with an old condenser enlarger, and can't get rid of it, there are ways to have some fun anyway.