Writing f-numbers with a hooked f?

I noticed that f-numbers are sometimes written using ƒ or "hooked f"

instead of f, so that searching for, say, ƒ/1.4 on Google gives different

search results from f/1.4. Does anyone know the history behind ƒ vs f?

There is a <a href="http://en.wikipedia.org/wiki/%C6%91">Wikipedia article on

ƒ</a> but it doesn't contain any references to photography or optics.

It is apparently a 20th century typographic convention that grew up over time: http://en.wikipedia.org/wiki/F-stop#Typographical_standardization

Jin, that's useful information, thank you! I usually use f-number as a convention when writing about aperture settings in general, and f/something when I am mentioned a specific setting. Thus, I would write "I used f/5.6 as my f-stop." If I am reading your reference correctly, then I had been doing it right. I've never known how to do the elongated 'f' on a standard US keyboard.

Wigwam,

 

It's simple. In a word processor (nearly any word processor), select the letter or group of letters and press CTL-SHIFT-I, or select "Italic" from the font pull-down menu. In Photo.net, you have to know a little HTML, which is also done with a "standard US keyboard". If you're referring to a "standard US typewriter", I'd have to check in my attic or The Smithsonian ;-)

Test, Test, Test

In HTML, there's a difference between <em>f </em>(<em>f</em>)

and <big></big> (). The first is a lower case "italic F" while

the latter is a lower case "Latin F with Hook." The difference is more apparent with a sans-serif font.

<a href=" F-numbers when writing by hand</a>

It's common to use italic and other typographical differentiations of an alphabet when describing mathematical terms. The 'hooked f' in this case means 'focal length' when calculating aperture diaphragm openings. They're calculated as a ratio of the focal length to keep us photographers from going through the number crunching of exposure when we change from one focal length lens to another.