Quote - The 50mm matching human eye has more to do with viewfinder than anything else.

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 SLR is not going to give the same magnification in a medium format camera, nor in a DX format DLSR.

 

The "normal" focal length of a given film or sensor format is roughly its diagonal. For 35 mm film, it's actually 43,27 mm, for classic middle format (6 x 7) it's 88,87 mm. What remains constant (apart from the aspect ratio) is the angular field.