Here are a couple for observation. The Jena 50/2 is no slouch but, IMHO, the 50 1.5 outshines between 2.8 and 5.6, and the full open f1.5 painterly "look" or "glow" is not quite attainable with the the F2 Sonnar. Still, they are both wonderful lenses to use.
Opton Sonnar 50 / 1.5 wide open at about 1m on Tri-X @1600
Jena Sonnar 50/2 wide open at about 1m on Ektar 100
EDIT: I should add that I use a 1A or 1B skylight on every lens, so the warmth in these photos is not accurately representative of these lenses sans filter.