R8 Autofocus Hypothesis

[Michael Reichmann <michael.reichmann@alphanet.net>]

The article below was posted today to the Photoforum on Compuserve.  It
was posted by a fellow named Donald Ingram, 100664.2005@compuserve.com .

I am reporting it here (without his express permission, but since it was
on a public forum I'm presuming he won't mind), because it really is
quite thought provoking, even if not necessarily accurate.

Michael

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The Leica R8 already has built in AF

How does it work and why are Leica keeping quiet ?

The camera's metering uses a multi-element CCD sensor to obtain
average/spot/multi-segment readings. There are sufficient elements in
the sensor array to obtain contrast difference information for autofocus
use.

The R8 has a series of electronic contacts on the lens mount:  these are
used to power the focus motor and electronics in the new lenses.  These
lenses or rather focus mounts ( for the 300 f 2.8 and 400 f2.8 heads
first) contain a small embeded micro controller which 'speaks'  to the
camera body to continiously read out the data from the CCD
focus/metering array. The information from the camera body is processed
in the lens and is used to drive the high speed ultra-sonic linear motor
in  the mounts internal focusing system. Options such as AF tracking
mode are set  on the lens mount rather than on the camera body. 

The 2 large lithium batteries in the camera are required to provide
sufficient current for the motor when the motor drive is detatched.

Leica has taken this route in order to get the R8 on the market in time
for Photokina, but has not yet had time to develop the hardware/firmware
for the lens mounts. The AF mounts will not reach the market until next
year provided  Leica can first get the focus system's software routines
to work reliably.  However if the CCD meter/contrast system proves to be
too much of a compromise they can still pretend that the camera was
never intended to auto focus. 

If all goes well and the AF mounts are launhed, Leica will no doubt
state that AF is only realy needed in these particular lenses ( i.e.
those used by sports/action photographers) and the AF is actually
unnecessary in wide angle lenses and can be a hinderance in macro
lenses. 

Now I will come clean: all of  the above is all educated guesswork. 

But if I was the electronics engineer working on the project, that's how
I would split the task up.

Has anyone else reached the same conclusions or even seen a factory
prototype ?