Schneider-Kreuznach made quite a few very small enlarging lenses and most of them are really good. The 50mm f4 with 4-bladed aperture, 50mm f4.5, and 80mm f5.6 are few of them. When I tried the 80/5.6 on the Canon 5D Mark II, I was very surprised to find out how good it is. Enlarging lenses are optimized for close up use, but even at infinity, the lens is extremely sharp, from corner to corner on full frame. Not too many lenses can make that claim, and let's not forget that tiny enlarging lenses like this are extremely cheap in the used market. Admittedly, the use of this lens is kind of limited. Even though the focal length is good for portrait, but the small maximum aperture makes it unsuitable if you want shallow depth of field. It's not long enough as a telephoto lens, but if you do make use of it, the optical quality is simply amazing, especially when stopped down to around f8 or f11.
If you like to fiddle with old stuff, it might be worth the $5 to pick one up in the flea market, or photo show. This focal length and the 75mm, is about the shortest focal length you can use on the Canon EOS mount and still get infinity focus. Anything shorter can only be used as macro lenses with a bellows on EOS.
Small Wonder next to a penny - Photo taken with 5D II & EF 40mm f2.8 STM. Click for larger.
On the helicoid - Photo taken with 5D II & EF 40mm f2.8 STM. Click for larger.
New BridgePoint Hospital in the evening. Canon 5D II & Schneider Componon 80mm f5.6.
Silhouette - Canon 5D II & Schneider Componon 80mm f5.6.