Originally Posted by gorbas
It's really important to bear in mind that the lens was not developed with digital sensors in mind. Because film tends to be much more forgiving, a lot of the "legendary" lenses from that period 50s and 60s, maybe early 70s -- basically the golden era of manual focus lenses -- perform pretty poorly on digital, while continuing to be incredibly charming on film.
I'm sure someone could offer you a correct and more in-depth explanation of the physics, but I know it has a lot to do with film having physical depth, as well as emulsions not requiring perfectly aligned photons to expose them. A good way to think of it would be the increased ease of hitting a paper plate with a baseball (film), in comparison to hitting the back of a bucket that was turned horizontally on its side (digital).
It's unfortunate that you were so discouraged...