RE: [Leica] arggghhh... rant at Keeble & Shucat...

["Clive Moss" <chmphoto@sbcglobal.net>]

> -----Original Message-----
> From: owner-leica-users@mejac.palo-alto.ca.us 
> [mailto:owner-leica-users@mejac.palo-alto.ca.us] On Behalf Of 
> Eric Welch
> Sent: Thursday, July 31, 2003 8:44 PM
> To: leica-users@mejac.palo-alto.ca.us
> Subject: Re: [Leica] arggghhh... rant at Keeble & Shucat...
> 
> 
> No, that's not true. The longer the focal length the less accurate a 
> rangefinder is. Because the base of the rangefinder (based on the 
> distance between the two windows that make up its base) 
> determines the 
> accuracy of that rangefinder.

Exactly correct. Nothing to do with the lens that is attached.

> It becomes smaller in proportion to the 
> focal length as the latter increases.

Also true

> Thus less accurate in absolute 
> terms.

Not true.

> Why do you think Leica sells bodies with different viewfinder 
> magnifications?

This does have an impact on accuracy -- but nothing to do with the lens
attached to the body.

> Why is an M6 more accurate than a CL? Because of the 
> rangefinder base! 
> It's wider on an M body. Why is it harder to focus accurately 
> with a 75 
> Summilux wide open than a 50 Summilux? It's in part because the depth 
> of field is shallower. But it's also harder to place that plane of 
> perfect focus where you want.

All true

> Because the rangefinder is less 
> accurate 
> with that lens because the "base" is narrower for the 75 than 
> it is for 
> the 50 in proportion to the focal length.

Nope. The base does not change. It does change relative to the focal length,
but so what?
 
> This is basic physics.

Nope. It is Geometry and Trigonometry.
Remember the days of separate rangefinders? Little gizmos based the same
principle as current Leica rangefinders that we clipped into the accessory
shoe, took a reading, and manually transferred the reading the lens. Lets
say the actual distance was 20 feet, and the measured reading was 19' 6".
The inaccuracy of 6" is constant, no matter what the lens is. For some
lens/aperture combinations -- good enough. For others, not good enough. The
accuracy/inaccuracy is the same. Increasing the magnification of the
viewfinder will enable you to discern smaller errors, and thus improve
accuracy -- but independent of the lens in use.

This really is not worth arguing about. I do not enjoy these kind of
quibbles, so I will stop quibbling. We do actually agree about the basics --
that it is more difficult to hit exact focus using a rangefinder with large
aperture, long lenses than with shorter, smaller aperture lenses.

I will close by saying that I checked out your web site. Some super pictures
there.
Peace.
- -- 
Clive
(Who are Keeble & Shucat anyway?)
http://clive.moss.net

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