[Leica] Re: CL lenses on the Leica M

["Doug Richardson" <doug@meditor.demon.co.uk>]

In his book "Leica CL", Theo Kisselbach (who I believe was a former
head of the Leica Academy) says:

"Screw-mount Leica lenses and bayonet mount lenses for the Leica-M
cameras have a differential helical motion, i.e. the contact surface
for the range-finder roller is displaced parallel in focusing. In
order to achieve a compact, light construction with the Summicron-C f/
2,40 min and Elmar-C f/4, 90 min lenses for the CL this system was
dispensed with. Both the CL lenses have high curvatures. Consequently,
although they can certainly be used on the M-cameras it is possible
that the rangefinder will in some cases show certain small
inaccuracies. Before using the CL lenses on M bodies, therefore, you
should check whether the rangefinder control is accurate. The thing to
check is whether at infinity setting the two images are perfectly in
register."

Regards,

Doug Richardson