In article <310CD1E5.774@AISystems.be>, Jan.Rosseel@AISystems.be says...
(most of post deleted)
>Some people go to a great extent to "proof" the quality of their lenses.
>I once heard a professional photographer say that Leica lenses had more
>depth of field than other brand lenses. So, Leica can actually beat >laws of physics thesedays? Wow...

Hmmm.... Actually, he may have been right.... (I am joking! ;-), ;-)
Since DOF depends on the perception of relative sharpness, if there
is no good reference (like an area of the photo that really IS sharp),
a softer lens may appear to have greater DOF than a really sharp one.
So, too, may a lens that renders the out of focus image with sharpish
edged circles of confusion appear to have different DOF from a lens
that renders the circles softly.
Hope This Helps