I need some inputs about the difference between .ttf and .otf, I know about how the formats have different curve logics, but what does that really do to the final output and how the fonts work? Is .ttf vs. .otf only a matter of taste and design preferences or?
As this is not a tool-(glyphsapp)-specific question, you could use external information:
The difference for the user is becoming less and less.
- Hinting is the biggest difference.
- Many consumer software environments prefer TTFs over CFFs, or do not even recognize CFFs.
- Some special problems with complex paths (performance, PostScript errors) in CFFs. TTFs may be safer to use, generally.
- As a designer you have more control over the CFF outlines because this is what you edit and what is exported into an .otf, while TT outlines are a result of automatic conversion.
- CFFs work a little better in professional DTP apps such as InDesign.
There are a number of other technical and compatibility differences between the different font formats, but these don’t directly affect most designers. OpenType fonts are related to TrueType fonts, but they incorporate a greater extension of the basic character set, including small capitalization, old-style numerals, and more detailed shapes, such as glyphs and ligatures . Moreover, it can also be scaled to any size, are clear and readable in all sizes, and can be sent to any printer or other output device that is supported by Windows. So, OTF is undoubtedly the more robust of the two options. It has more features that are intended to allow typesetters and designers flexibility to provide incremental changes designed to improve the overall look of a piece.
All of the mentioned features of OpenType fonts are also available in TrueType fonts. The confusion might be that “TrueType” fonts has changed meaning in the last 20 years. Nowadays, both are very similar and differ only in the way outlines are defined and stores (quadratic curves (TrueType) and cubic curves (CFF)).
Hinting is the biggest difference
In what way? I’m told (and based on my experience with TTFs) that CFFs are easier to hint and the quality of PDF and generally screen viewing of OTFs are superior to TTFs. Is that true?
In OTF (CFF PostScript), “hints” really are hints. You indicate stems, baselines, cap lines, x-height, and other features of your font that you consider important. You leave it to a “smart” rasterizer to preserve these features as best it can at various resolutions.
In TTF, there are actually instructions, not “hints”. The rasterizer is “dumb” and must be told what to do with the outlines by the instructions. The instructions have to take into account the resolution of the output device (in pixels per em), whether it is grayscale or monochrome or RGB (which can have subpixel antialiasing).
TTF gives you very precise control of how a font will be rasterized, but strategies that work for monochrome displays may not work well for grayscale or RGB and vice versa. If a new kind of device comes out, you may need to update your fonts to take advantage of it.
OTF hints give you less control, but are device independent. You hint a font once and it is done forever. If a new device comes out, you don’t have to update the font to take advantage of it. The smart rasterizer for that device will use your hints and do the best it can with them.
Most of this is a non-issue on Apple platforms. Apple mostly ignores hints in either format and uses its own methods for improving the appearance of fonts on devices. Hinting mainly affects Windows, Linux, and Adobe apps, which use their own rasterizer rather than the one built into the OS.
Oh yes I know! I had no idea about this issue until I saw my TTF fonts on the Windows! terrifying!
I think it is more so for Arabic script or other scripts that cannot provide an identifiable measurement criteria such as stems etc.
But few years back I used an excellent tool for auto-hinting and things improved substantially. Still nothing like the look on the Mac.