For what it's worth I made good experiences with not taking one single source too serious. I'd rather have a look at several sources if possible, look where they agree and what doesn't fit the picture and trying to find out why things might disagree. Ken is not very fond of 50mm lenses after all and says "I no longer even own any 50mm lenses". I think that is a good reason to take his judgement with more than the usual pinch of salt.
Originally Posted by Paul_Baker
PS.: Neither vignetting nor falloff should be reagerded an exact term as used buy photographers. If you try to do so you will run into trouble faster than you can say Waxahatchie.