Voigtlander Viewfinders
Voiglander produces the largest selection of accessory viewfinders designed for full frame 35mm cameras. SEARCH by the original designed focal length such as "Viewfinder 12mm"
(remember the mm immediately after the focal length, no spaces), or format such
as M43, NEX or RD1. Crop factors vary with camera format: The Leica 8/8.2 have a crop factor of 1.3x, the Epson RD1 and NEX 1.5x, the M43 2x.
For example shooting a 12mm lens: on a full frame camera like the M9, use a 12mm viewfinder.
For a Leica 8/8.2, 12x1.3=15, so the closest would be a 15mm viewfinder. For the
1.5x RD1 and NEX, 12x1.5=18mm, so use a 18mm viewfinder. For the 2x M43,
12x2=24, so use the 25mm viewfinder. Clicking the CART item from search or
category will give you a 2nd, detailed cart. Linked from that you will
find linked a detailed INFO page.