Google for example using letter-spacing on lowercase on Roboto
because if the type is smaller, it gives it a bit more room to breathe and makes it easier to read
This is their own font, why make it unreadable in small sizes?
Letter spacing and type size is a fixed linear relationship. If they made more legible in small sizes (i.e. more space overall between characters in the font files), then they'd have to recommend reducing the letter spacing at medium point sizes, and further reducing the letter spacing at large point sizes.
Basically a font has its own expected usages and specs like letter-spacing, kerning and tracking is set based on that usage. Fonts like Helvetica Now and Apple SF has variation for small text, whose letter-spacing is significantly looser than its default variation.
https://developer.apple.com/design/human-interface-guidelines/ios/visual-design/typography/ Yeah, you are right, thank you. But how to specify this numbers? Do we have a rule or it's only eye measured?
there are no hard rules for this stuff, it's about eye and subjective taste
Just, Why not?
Upcase makes it easier to read, I always do this with button size lower 12. In the case of Overline, because it's small so we need upcase to read or maybe just make this bigger, 12 for example. Just don't know why the Google button size is 14px, it's really big.
You call 14px font big? Oh my.
What is this, text for ants?
In my point, button text 14px and upcase is really big :)
14px is as small as I'd go for anything in a
<p></p>and I wouldn't consider that 'big'. Button text below 12px seems crazy small to me. Most people prefer 16px+ for reading.