"bmoag" wrote in
:

Sorry to rain on your parade: it is optically impossible to confirm
perfect, let alone optimum, focus on the small screens built into live
view cameras. The image will always appear to be sharper than it
really is on these tiny screens.
You can test this yourself easily, but that would require a discipline
of thought and technique . . . .

I can see the focus change on my 50D zoomed in 10x, rotating the barrel as
little as stiction allows.