Nikon F5 and D3 Shared Genes

Viewfinders have two three important statistics:

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 DK-17M adapter increases magnification by 1.2x and can be used in the F6/D2/D3 series cameras. The DK-21M is meant for the prosumer DX SLRs.

Nikon, and all other vendors, cheat when they report the viewfinder magnification of APS-C 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 APS-C 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 APS-C 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