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 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.

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 |