It of course depends on the shape of all other letters…

For ideal* readability not even Italics should have a descending "f".

* But never perfect!

hhp

Julia, willkommen bei Typophile!

For ideal* readability not even Italics should have a descending "f"

thats quite nonsense. Never mind!
obviously Hrant is eager to hard-proof a newbie ;-)

Fedra demonstrates that a descending f (and possibly: ſ, ß) can work pretty well. By the way, it is also possible with serif faces. Did it myself.

Thanks for your replies.

Andreas, danke :-)

I also think that a descending "f" does not necessarly worsen the readability. I noticed several serif typefaces where it appears more common to me. I fear that it might look a little incorrect in sans typefaces, although fedra is a positive example, like Andreas said.

It's really quite simple: it has nothing to do with "incorrect",
it's that we read "expected" boumas and a descending "f" destroys
those pre-built expectations. How quickly can we build a given
bouma expectation that over-rides (or at least coexists with) all
our previously built expectations? Good question. Until somebody
can convincingly answer that question with "in minutes", I will
stick with the view that a descending "f" harms readability.

Now, it's entirely OK to sacrifice some readability (it's never
perfect anyway) intentionally* but it's not OK to pretend no
price is being paid. THAT is nonsense, as is thinking that one
can evaluate readability by reading a little bit.

* I've done that myself in Patria by making
certain letters atypically wide, in order to
reinforce the character of the face.

hhp

I've designed many types, some quite unconventional, but have never considered roman "f" with descender as an option.

However, I've given descenders to some italic sans "f"s, in genres where it's not the norm, to signify an "old style" sensibility.
e.g. Alphaville, Figgins Sans and Sensibility.

That's not to say I consider the "f" in Fedra a mistake, it's just not my thing.

That surprises me some Hrant. I would have thought you'd be in favor of it, since it provides extra information to the eye since no letters (except þ) have both an ascender and a descender. Or does it cause too much relationship to the written form where it does descend (always cursive, sometimes print)?

a descending "f" destroys those pre-built expectations

Hrant, why do you think it destroys expectations? Italics have their own style, changing many upright forms. I believe reader expectations are mainly determined by the kind of design he/she was used to –and italic f with descender is an usual form since long time.

I agree that a no-descending italic f may be more coherent, but I do not see readability sacrifice in it. Anyway, this is an interesting question.

I have another kind of worry. Descending italic f is hard to diferentiate from f with descending left hook (Unicode 0192, companion to uppercase 0191). This may justify a no-descending f in a font supporting non-European languages. (Actually, many less used Latin characters conflict to the usual way italics and swashes are designed.)

Julia, for the reason above I do not recommend to use a tail if the font aims wide language support.