[Leica] RE: RE: who knows where I want to focus?

[Jim Brick <jim_brick@agilent.com>]

Hey Félix,

Look at some lens resolution charts for Canon and Nikon lenses. They list
resolution in two columns. On column for autofocus, one column for manual
focus. Manual focus resolution is ALWAYS better than autofocus resolution.
Why? Because an autofocus mechanism is incapable of "critical" focus. How
do I know this? Because this is part of my work. I just wrote some
autofocus algorithms and the electronic signal data that is returned from
the AF sensors is incapable of making perceptual differences between being
critically sharp and "just" being in focus. You either build a signal
histogram in software or you get a digital voltage peak at the point where
the camera electronics thinks what you are looking at is in focus. To the
AF sensor, it's just numbers, and lots of them. No critical human brain
involved.  These sensors have a high rate of subject failure. They don't
know what it is, specifically you want to focus on as they only see voltages.

AF is OK for some tasks. But totally inept at many. And the problem is that
you won't know it until you get the film processed. When you personally are
focusing, well, the camera will deliver focus on exactly the part of the
subject that you wanted in focus. Why? Because that is where you personally
focused.

Jim

At 12:19 AM 6/2/01 +0200, Félix López de Maturana wrote:
>"I'll gladly stand by my original statement, I already have the best
>autofocus system ever devised, my brain (both sides), my right eye and one
>of my hands (which one, is camera dependant)."
>
>Austin,
>
>Glorius...Perhaps  you had to register this mechanism : the perfect
>autofocus Austin's brain (both sides and up and down), eye and hand. Maybe
>Canon or Nikon or other damned rubbish camera maker do wish to purchase it
>it...
>
>Kind regards
>
>Félix