Otf vs. ttf

mauro sacchetto
mauro sacchetto Posts: 353
in Font Technology

On the net, many treatises talk about the .otf format as "stronger" or "more stable" than the .ttf, and the fact that the .otf have features that the .ttf do not have, like ligatures, small caps, alternates etc.
See for example this page (I don't know how old):
Yet many .ttfs allow me to use those features not only with LaTeX, but also on LibrOffice. Now what is the current situation? I don't want to open the usual inconclusive flame, but are there reasons to prefer .otf to .ttf?

Comments

  • Hrant Հրանդ Փափազեան Papazian
    Hrant Հրանդ Փափազեան Papazian Posts: 2,044
    edited May 2019
    One thing that makes OTF more robust is not the fault of any format per se, but that people can design imperfect cubic bézier curves that translate incorrectly to quadratic (most commonly, missing inflection points) and you often don't notice until it's too late.
  • mauro sacchetto
    mauro sacchetto Posts: 353
    A "very technical" reason, even if relevant to the designer.
    But, from the point of view of the simple user, can the two formats now be considered equivalent?
    Among other things, if I'm not wrong, the rendering of .ttf on Windows at low resolutions is better than that of .otf, which instead presents problems that require special precautions
  • Erwin Denissen
    Erwin Denissen Posts: 299
    edited May 2019
    TrueType is a scalable font technology designed by Apple Computer, and has been superseded by the OpenType format. However people still refer to TrueType fonts, while in fact 99.9% of all fonts that come with Windows are OpenType fonts.

    There is no such thing as an .otf or .ttf format as those are file extensions. Historically .ttf was used by fonts with TrueType based outlines, and .otf for CFF based outlines, but .otf fonts can also contain TrueType based outlines, so the extension can't make the distinction between TrueType or CFF based.

    Both TrueType and CFF based flavors are called OpenType fonts nowadays, hence it is the OpenType specification. What counts is the availability of OpenType layout features, which can be included in both flavors.

    You can use a font manager to see which OpenType features are available in a font.


  • mauro sacchetto
    mauro sacchetto Posts: 353
    But why, if I save a font file in ttf, do I seem to have less rendering problems in Windows than in the .otf format? Or does this imply something wrong with my procedure?
  • Erwin Denissen
    Erwin Denissen Posts: 299
    That has nothing to do with OpenType features, but strongly relates to the outline format, the hinting, and the rasterizer.
  • mauro sacchetto
    mauro sacchetto Posts: 353
    ok, very clear and definitive answer. Thank you
  • André G. Isaak
    André G. Isaak Posts: 632
    mauro sacchetto said:
    But why, if I save a font file in ttf, do I seem to have less rendering problems in Windows than in the .otf format? Or does this imply something wrong with my procedure?
    While the .otf extension can technically include either Postscript (CFF) or TrueType outlines, most font design applications assume you want Postcript if you output as .otf and TrueType if you output as .ttf. That's why you see a difference.

    Windows typically does better with TrueType fonts provided they are well-hinted. On the Mac, you likely won't see a difference. I can't comment on rendering in Linux.
  • mauro sacchetto
    mauro sacchetto Posts: 353
    There is a large debate about Linux rendering and its tools.
    From a practical point of view, I see all very well on Linux,
    without all the troubles od Windows rendering

  • Claudio Piccinini
    Claudio Piccinini Posts: 681
    Erwin Denissen said:
    […] Historically .ttf was used by fonts with TrueType based outlines, and .otf for CFF based outlines, but .otf fonts can also contain TrueType based outlines, so the extension can't make the distinction between TrueType or CFF based.

    And not historically? I mean, if there is the .TTF extension I assume there is Truetype hinting (and additional points), even now that the format is superseded and all are de facto compliant with the Opentype specifications.
    I thought that the extensions were preserved because the outlines and (auto)hinting were actually different.
  • Claudio Piccinini
    Claudio Piccinini Posts: 681
    John Hudson said:
    The .ttf extension was preserved because the TrueType OT format was designed to be backwards compatible to systems that didn't support OpenType Layout tables, so it was possible to install a TrueType OT font on an older system that wouldn't recognise the .otf extension and have it function just like older TrueType fonts with the .ttf extension.

    This backwards compatibility aspect of TrueType OT fonts has persisted even to the most recent versions of the OT format. It is possible to install a variable OT font on older systems without OT variation support and the default instance of that variable font will function as a simple, static TTF.
    Thanks much for the learned input. That’s also more or less what I remembered, now that you remind me!

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