A question of optics

When I look at the view from old 35mm Nikon FG film camera with an 85mm lens, it is about the same as the view on my Olympus XZ-1 with the zoom lens at full tele, or 112mm,

Practically, it doesn't matter -- I can use the XZ-1 as a monochrome viewfinder for the FG without any problems... I don't need an exact preview match.

But I'm curious. 112 minus 85 leaves 27mm missing... more than differences caused by the FG's 93% viewfinder. What's going on?

I don't know optics. Am I incorrect to expect close angle-of-view similarity between two lenses that are very different in physical size? If so, why?

Thanks in advance for thinking about this...

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Jonathon Donahue -- Olympus XZ-1 tips at http://jon404.com