First is the new Apple-created Maps, which is one of Apple's big gambles in some time. It's also included in the new screens of Siri. You can find it featured prominently in the restaurant recommendation page, for example.
Avenir is included in OS X too. In fact, you can find three typefaces of the family Avenir, Avenir Next, and Avenir Next Condensed , all in a variety of weights. Apple is not using it in any OS X application or at least I can't find it anywhere. Would Avenir take an special role in OS X too? Perhaps Apple will unify all of its system typefaces one day, if iOS and OS X finally merge into a single operating system. And perhaps that day everything will be Avenir—I hope not, since Helvetica Neue is much prettier and more legible.
And if you're wondering why it matters when a company chooses one typeface to replace another, just remember: it could have been Comic Sans. The strokes of the letterforms kind of bleed together as you saw in the above example.
Additionally, tracking smarts are built into the platforms. I just said that the higher x-height of San Francisco makes it easier to read on-screen, so what good could it do to make the cap height smaller?
This has the added benefit of making the x-height seem even larger, relative to the cap height which may encourage developers to use larger text sizes. This is part of what makes San Francisco the perfect typeface for Apple. After all, it boasts 51 variations. But, San Francisco has a healthy set of options, optimized for display on screens.
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Each of them have multiple weights in their display and text versions. San Francisco has a wide range of variations. The implementation of San Francisco across the various platforms makes it easier for developers to choose monospaced, or proportionally-spaced numerals. A situation where monospaced numerals above are more ideal than proportionally spaced numerals.
You can opt out of them with a simple API shortcut.
Since Apple devices are often displaying the time, it makes sense that, in San Francisco, the colon is now vertically-centered by default developers can opt out in their code. This allows the counters the spaces inside of the letters to be larger — which means more pixels to communicate the form.
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Tiny, text-sized type on a tiny screen presents different typographic challenges than larger, headline-sized type on a giant screen such as a TV. Small text needs to be readable, and large text needs to be beautiful. These goals are sometimes at odds with one another. Notice how the body copy blends together in the display version.
Conversely, the body copy in the text version is comfortable to read. However, the headline set with the text version is clunky due to more spacing, and heavier strokes , while the headline set in the display version casts a more even texture, thanks to some of the adjustments illustrated below. Some of the adjustments made between the text and display versions of San Francisco. Source of Glyph outlines.
The letters are often too close together, especially at smaller sizes. This makes it hard to read in large blocks of small text. The strokes of the letterforms kind of bleed together as you saw in the above example.