Chloe writes:

Enlargement ratio has SFA to do with depth of field. It's all about
focal length and aperture.

Focal length, aperture, focal distance, and circle of confusion, surely?
All of those enter into the real formulas.

And the choice of suitable circle of confusion is conventionally based
on film size and intended degree of enlargement; those last two
amounting to "enlargement ratio".
--
David Dyer-Bennet, ; http://dd-b.net/
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