Out of several, I have two classic vintage 50mm lenses.
1. Carl Zeiss Jena 50mm, f/2.8 Tessar
The lens mount has been converted from M42 to Nikon F mount. Through an adapter I use it on my Fuji-X1. See how it performs:
2. The second lens is Yashica Yashinon DX 50mm f/1.4. Also converted from M42 to F mount and the following is by using it on Fuji X-E1:
Both are lovely lenses and give quite pleasing out put. both draw similarly too and I thank much different than my Minoltas, Nikkors and Fuji.