Re: Lenses for CL

[Paul Schliesser <paulsc@eos.net>]

>Also, I've been told that the 90mm f4 lens that is intended for the CL is a 
>restricted f2.8 Elmarit, and close examination of the aperture blades 
>seems to 
>confirm this.  Why would Leica have done this?  Someone suggested to me that 
>this is something to do with the limitations of the rangefinder, but other 
>than a lens physically blocking the rangefinder I can see that any lens 
>could be a problem.
 

Simon,

The CL rangefinder has a shorter baseline, which means that it is not as 
accurate as the rangefinder in the other M-series cameras. This is 
basically the distance between the two rangefinder windows, but the 
magnification of the viewfinder also factors into the "effective" length 
of the base. The further apart they are, (or the wider the baseline) the 
greater the difference in angle between them as you focus at a certain 
point, and the more precisely it can measure that distance. The smaller 
rangefinder was a compromise made with the CL in order to make the camera 
more compact.

Because it cannot focus as precisely, Leitz chose to use a slower lens 
for the 90mm, because f/4 gives you a little more depth of field to make 
up for the less-accurate focusing.

This is also, I believe, the reason that they made an f/1.4 75mm lens 
instead of an f/1.4 90mm for the M-series. The 75mm is supposed to be at 
about the limit that the M rangefinder can focus with precision at f/1.4, 
whereas the d-o-f for a 90mm lens this fast would be too shallow to be 
useful.

You could use a 90mm f/2.8 on the CL, just don't use it wide open (or at 
least be aware that you are taking a risk with focusing wide open). You 
can also use some common sense; for instance, if you focus near infinity 
you will not have as much of a problem as when you are focused at close 
range.

You can use collapsable lenses, just don't collapse them while they are 
on the camera! The meter is pretty delicate, and you can easily damage 
it. Some wide angle lenses protrude far enough into the camera body to 
foul the meter, so you should avoid them.

- - Paul