Your motto could be.
Originally Posted by Q.G.
I commit to my motto, however. :-)
Realistically, I don't think there's any "optimal" FL, however the FL is most definitely attached to how much space the photographer shares with the subject - which is further picked up on by the viewer of the images produced from it.
In terms of 135, a 50mm can convey separation, whereas a 20-35mm can convey involvement or immersion because you had to be close to pull off a good shot.
Sometimes separation is pertinent - however most of the time immersion is much more powerful. Mainly because it takes involvement and commitment.
Caveat emptor: I'm not a rocks and trees photographer.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.