Re: [Leica] Re: MR meter for M3

[InfinityDT@aol.com]

In a message dated 10/1/98 5:55:40 PM EST, dkhong@pacific.net.sg writes:

> Hi friends
>  
>  I am exploring the possibility of attaching a working meter on my M3.
>  Which models are suitable for this camera?   
>  
>  I understand that some of the old meters use mercury batteries and some are
>  selenium types. Would it be preferable to get a selenium model since
>  mercury batteries are no longer available in many countries?
>  
>  Dan K.

                         All the Leicameters designed for "M" models will
couple to the shutter-speed dial and work.  Finding a selenium meter that
still works is getting harder and harder.  Then, they have about 1/2 the low-
level sensitivity of the later CdS models. They made a booster cell attachment
for it, to some avail, but it was not very ergonomic to say the least.  The
selenium models also read a large angle of coverage, so they're easily fooled
by contrasty light.  Unless you keep them covered when not in use, they
fatigue from prolonged exposure to bright sunlight, and [temporarily] become
inaccurate.  You are certainly better-off with a MR or MR-4 meter (both CdS
types) which read an area equal to the 90mm frame-lines in the .72-finder M's,
so probably the 135 frame in your M3 would be a rough approximation.  I
understand that the on-switch of the MR (switch is small, T-shaped, on the
meter's flat side) is not longer obtainable, so it's more difficult to repair.
The MR-4 (last one made, up until the mid 80's) has the top-mounted switch,
which is nicer if you ever use it with the M4-series as it leaves room for
working the rewind crank.  CdS meters are slower-reacting than the more modern
silicon cells, but they're just as accurate.  Using the Leicameters, you still
have to take the camera from your eye to read the meter and set the aperture;
also, you can't mount a shoe-flash or accessory viewfinder along with the
meter.  One in good shape will run close to US$200.  All of them took mercury
batteries.  They can be adjusted for the voltage of the alkaline replacements,
but not for the discharge curve.  Mercurys are linear, i.e. they maitain
constant voltage until they die.  Alkalines lose power as they discharge,
which without a regulator means the meter readings become less accurate.  The
zinc-air "Wein" cell replacements don't have that problem, but they are
expensive and short-lived.  There's a company in Arizona called CRIS that
sells an adaptor the size of a PX13 or PX625 into which you put a MS76
(silver-oxide) battery.  They say it has micro-circuitry that matches the
mercury performance exactly.
After all, I have to say that I much prefer a handheld meter.  I use the
Sekonic L-408 digital that reads 5-deg spot and incident, ambient and flash,
shutter or aperture-priority, and it has a memory function for multiple
readings.  It takes one AA cell, fits your hand, and it's splashproof.  I use
it even with the M6 whose metering area is often too large especially with
wideangle lenses.