Re: [Leica] RF myth? Magnifying glass over viewfinder

[Gaifana@aol.com]

A lens a short distance away from the eyepiece does make a difference. One 
too close will just act as an eyesight corrector. Look at all the SLRs with 
focus magnifiers - they do work. In the 1950s Canon used a variety of zoom 
finder that had 0.75 for 35mm, 1.0x for 50mm and 1.5x for longer lenses, 
presumably with the idea of boosting accuracy.

Which brings me to another idea - why are people so hung up with effective 
base length? Very simply geometry dictates that the wider the actual base 
length, the better distance-differentiation at long distances (let's call 
this theoretical accuracy). All Leica M bodies and the Hexar RF share the 
same basic geometry (and if I am comparing the drawings correctly, exactly 
the same design).

Effective base length is the product of the finder magnification and the 
actual base length. I can only conclude that this has nothing to do with 
theoretical accuracy and everything to do with practical accuracy, viz. 
longer effective base length means more magnification means it is easier for 
a human to focus the lens. That's where the HM or the M3 has an advantage 
over an M6. It's easier for *people* to focus. The rangefinder is not 
inherently more accurate. By analogy, a gun with a scope on it is not more 
accurate than one without.

But then you have to add the tolerances (or multiply) to get another factor 
in the accuracy equation. A Leica-style RF has 130 parts. That's a lot of 
tolerances to add up.

Dante

In a message dated 12/8/99 2:03:29 PM, le@ilog.fr writes:

<< Hi,

It's maybe a stupid question but I'd appreciate some explanation.

Assuming that I put a good quality magnifying glass between the viewfinder
and my eye and the RF is fitted with a demanding lens as the 75mm.

- -  Does that improve my focus ability thanks to a better vision of both
images merging. But it's of no use because the actual focus accuracy is
still the same because the internal prisms are the key factors.

- - that does improve the actual focus accuracy. Then why no one talks about
it ? >>