They hardly relate at all. The coverage circle is determined by the design of the lens itself.

Angle of view is a completely different thing; it's a function of focal length and format size.

BTW, that's not "format diameter" in your equation, it's "d" which is the length of film in the direction you want to calculate angle of view. This is required because most film formats are rectangular and therefore have a different angle of view for the long side vs. the short side. The correct equation is alpha = 2arctan (d/2f), and it works for all formats. Don't forget to use consistent units of measure for "d" and "f."

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