[Leica] sharpness, was New 50 R Summilux

[Mark <mark@steinberg.net>]

Chris Bitmead wrote:
> 
> 
> A fast 50mm will never be anywhere near as sharp as a fast 80mm
> lens. It is a fact of life that no 50mm f1.4 lens will measure up
> to an 80 f1.4 lens.

why ?

is this a function of how "sharp" is defined ?

if "sharp" is defined as:

"the breadth of a hard edge on a negative or slide"

(in other words, the ability of a lens to cast an image of a
hard edge onto a film accurately)

surely the influence of the lens design would play a much greater
factor than the focal length ? (this talk of APO lenses for instance,
if the lens is "non-APO" then there would be a color cast along the
edge (thereby broadening it) ? and i don't see APO short-focal-length
lenses, so is it axiomatic that short focal lengths don't require 
color correction in the same way long-focal-length lenses require it ?)

or am i being stupid ?

m