Nikon Viewfinders
Viewfinders have two three important statistics:
 Viewfinder frame coverage tells you how much of the 35m frame is
shown. A 100% viewfinder shows the entire 35mm frame.
 Viewfinder magnification tell you how much the images are magnified
relative to naked eye, using the 50mm lens as a standard. The higher the
magnification, the easier it is to manually focus a lens.
 Eyepoint tells you how far away you can see the viewfinder along
with all the information. A high eyepoint is better for those wearing
glasses.
Amongst Nikon film and FX digital SLRs, the FM2N is one of the better
cameras for manual focusing due to the high magnification of the
viewfinder image of .86%. Compared with this, the magnification in the
D3 is .70%, whereas the F6 magnification is .74%. Nikon sells viewfinder
magnification accessories that increase the viewfinder magnification,
while reducing the eyepoint. The DK17M adapter increases magnification
by 1.2x and can be used in the F6/D2/D3 series cameras. The DK21M is
meant for the prosumer DX SLRs.
Nikon, and all other vendors, cheat when they report the viewfinder
magnification of APSC format DSLRs. A 0.94x magnification for the D300
sounds good until you realize that this is in terms of a 50mm lens,
which is actually equivalent to a 75mm lens on the full frame cameras.
To get a real sense of the viewfinder magnification of an APSC camera,
you need to know the magnification when using a 33mm lens, but no
manufacturer will tell you that. Some people assume that to get the
APSC equivalent magnification, you just need to divide 0.94x by 1.5,
giving you 0.63x, but I am not convinced that this is the right formula.
Visual comparison tells me that the D300 has close to effective
magnification of .75% when using a 35mm lens. I asked Nikon Support for
the formula to work out the magnification but they were not able to (or
not willing to) provide me one.
Viewfinder Specifications
Camera 
Viewfinder magnification using 50mm at infinity 
Viewfinder Coverage 
Eyepoint 
Nikon FM2N 
.86x 
93% 
14mm? 
Nikon FM3A 
.83x 
93% 
14mm 
Nikon F 
.8x? 
100% 

Nikon F2 
.8x? 
100% 

Nikon F3 
.8x 
100% 

Nikon F3HP 
.75x 
100% 
25mm 
Nikon F3AF 
.8x 
92% 

Nikon F4 
.7x 
100% 
22mm 
Nikon F5 
.75x 
100% 
20.5mm 
Nikon F6 
.74x 
100% 
18mm 
Nikon D3 
.70x 
100% 
18mm 
Nikon D5
 .72x  100%  17mm  Nikon D850
 .75x  100%  17mm 
Nikon D700 
.72x 
95% 
18mm 
Nikon F90x 
.78x 
92% 
19mm 
Nikon F100 
.76x 
96% 
21mm 
