# Are there two different versions of the \mathcal{F} character?

I've seen two different versions of the \mathcal{F} character:

Version 1:

Version 2:

Notice that the top horizontal line of the F curves down on the left much more in version 1 than it does in version 2.

Which of these is the preferred \mathcal{F}? I know that some of the calligraphic capital letters were improved at one point, but I don't know which version is the improved one.

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Hi MSC, please note that you can include images using one of icons on top of the edit box. You have now enough reputation points to do this. –  Martin Scharrer Feb 16 '11 at 23:19

The final version of Computer Modern's mathcal F is the second one. To see it, you can compile with metafont the file cmsy10.mf (located in [texmf]/fonts/source/public/cm/; be sure you have the latest version). Here is the result, after conversion in dvi format with gftodvi:

If you compare the type 1 versions of Computer Modern, you see that the Bluesky/AMS and Latin Modern versions both have the right version. However, old versions of Latin Modern have the wrong mathcal F:

This means that if you use a recent TeX distribution, you should always have the final version ofthe mathcal F.

As an aside, my version of Computer Modern Typefaces, although recent, still shows the old version:

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Thank you. Is there also a new-style bold \mathcal{F}? My system uses the new-style normal \mathcal{F} but the old-style bold \mathcal{F}. I've noticed this discrepancy in a few other PDFs I've found on the web, too. –  MSC Mar 10 '11 at 17:40
@MSC: yes, the bold also has a new version, but it's not in the Bluesky/AMS fonts. You can find it in the latest version of Latin Modern. So if your TeX distribution is recent, using \usepackage{lmodern} will ensure you're using the latest versions. –  Philippe Goutet Mar 10 '11 at 20:24

If you include the command \usepackage{eucal}, then \mathcal{F} will produce the curlier one and \CMcal{F} will produce the other. It's up to you to decide which you prefer.

To more directly answer your question: Including the command \usepackage{eucal} changes the \mathcal command so that it will produce the curlier one; omitting that package will make \mathcal produce the less curly one.

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It is not possible to use the eucal package to switch between the two versions show by MSC. Both of MSC's examples come from the Computer Modern font whereas eucal uses the Euler font, which is completely different (the most visible difference being that it is upright instead of slanted). –  Philippe Goutet Feb 17 '11 at 12:13
Oops! I guess I should have looked more closely at those "F"s. –  Phil Hirschhorn Feb 18 '11 at 1:17