[Leica] BESSA R3A or M7

[billgem at hotmail.com (Bill Marshall)]

On Saturday, Richard wrote:
>"I know nothing about lens & camera design, so several questions come to my 
>mind: - focus accuracy - it can't solely be based on the RF baselength, can 
>it? The RF mechanism must be incredibly precise to translate the small 
>amount of helical movement into RF patch matching? Also, how about the 
>helical tolerances of the lenses themselves. We know the CV lenses are 
>"good enough" & they have the know how to make a 35/1.2 lens, but are there 
>any potential issues there?"

Richard, isn't this precisely the point? The RF mechanism must be incredibly 
precise. Let's say hypothetically that allowable tolerances result in a 
focusing error of 1 mm. With a Bessa base line of 37 mm this is an error of 
2.7%, while on the longer ZI base line of 75 mm, the error is only 1.3%. So, 
the effect is twice as great with the shorter base line. The longer base 
line has minimized the impact ot tolerances or operator error.

How about the helical tolerances of the lenses themselves. We know that CV 
lenses are "good enough" . . . Isn't this exactly the issue at which Leica's 
marketing is directed. "Buy our lenses because they have tighter 
tolerances." CV good enough? I think that Leica would say; "Good enough for 
the customer base for which they are targeted, but where critical focusing 
is required, only Leica build quality will suffice."