The first one is what you see with your eyes.

*magnification number are all measured with 50mm lenses in infinity.

The top right is the viewfinder of ZX-M. 92%, 0.77X, 1.7 stops brightness lost.

The bottom left's the FM-10. 92%, 0.84X and 1.9 stops

The bottom right's the OM2000. 86%, 0.94X and 1.9 stops.

* for your information, here are the viewfinder spec. of some MF and AF cameras.

Contax AX ____95%__0.73X__2.2 stops

F5 __________ 99%__0.75X__2.4 stops

R8 __________98%__0.76X__1.6 stops

G2 __________91%__0.54X (with 45mm lens)__rangefinder

Elen IIe_______90%__0.72X__2.0 stops

ZX-5n________92%__0.78X__2.0 stops