As Michael Everson has told us, Dick Weltz said, on Typo-L:
> The florin sign, incidentally, is also used sometimes in type
> to indicate the f-stop of a camera lens,
> in which cases it is generally followed immediately by / .
I regard that as a misunderstanding.
The aperture of a lens is normally expressed as a fraction of its
focal distance, e. g. a=f/8 means that the focal distance is 8 times
the aperture. In due course, the various aperture settings on a camera
lens will be marked with fractions, such as "f/11", "f/8", "f/5.6" &c.
(if not the denominators alone, viz. "11", "8", "5.6" ..., are used).
In scientific typesetting, names of entities, such as "a" and "f"
in the above equation, are normally set in italics, whilst numbers,
operator-symbols, function names and units of measurements are set
in roman. In "f = 50 mm", e. g., the "f" (focal length, a physical
entity) would be in italics, "=" (an operator), "50" (a number), and
"mm" (a unit of measurement) would be in roman.
Likewise, the "f" in an aperture setting, such as "f/5.6", would be
in italics. It would definitely not be a florin sign, though its glyph
is similar, if not even indistinguishable from an italic "f".
Dipl. Phys. Otto Stolz
(This is one of the rare cases I make use of my degree :-)
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