[Leica] Leica RF patch size

[lrzeitlin at aol.com (lrzeitlin at aol.com)]

Ric and Richard,



There are two kinds of rangefinders typically used in cameras. One is the 
superimposed image type in which a RF patch image is overlaid on the 
viewfinder image and the RF image is shifted until there is no discrepancy. 
This type is used in the Leica screw mount cameras and the Contax. The other 
is the split image rangefinder in which the viewfinder image is split in 
half by a line running across its center. One half of the image is shifted 
until vertical lines show no offset. Kodak favored this kind of RF. It is 
also used in the split image finder assists of SLR's. The split image RF is 
more accurate than the superimposed image type since the human eye is better 
at sensing sharp breaks in a line than the precision of superimposition. The 
downside of the split image viewfinder is that it demands some type of 
straight or sharp lines in the scene. Accuracy of the split image RF is what 
makes its use possible in SLRs where the base length is only the diameter of 
the lens used.




The RF of the Leica M series is a composite. It is a superimposed image 
finder but the edges of the RF patch are sharp enough to permit use as a 
split image finder if desired. You can't do that with the fuzzy RF patch 
edges in the Barnack Leicas or in the Contax II.




It wouldn't be too hard to make a RF patch the size of the viewfinder. It's 
just that most photographers prefer to have an unadorned optical viewfinder 
for better composition.




Larry Z










I would think it is the size of the mirror.

One could build a viewfinder that was all split image, but it would be  
a bitch to look at two images all the time.

ric


On Sep 7, 2009, at 5:32 PM, Richard Man wrote:

> what determines the size of the RF patch? Is it the RF window on the
> front + the optics of the RF mechanism?
>
> For example, what does it take to build a RF patch 4x area that of
> Leica's? Will that make the RF mechanism too large or may be it will
> require a greater distance between RF window and the VF?
>
> Just idle wondering.