On the font front, this has taken a bit of a left turn. I’d originally been looking at the Noto Sans family of fonts as a means of creating some sort of single universal/fallback font. Well, that plan is dead. The font editing software I have (FontForge) can’t output the result of merged fonts without losing multiple anchor points (which destroys Thai and Hindi and makes me very nervous about the rest), so these separate Noto fonts need to stay separate in order to be usable.

Nevertheless I’m really growing to like these fonts – particularly the variant called “Noto Sans SemiCondensed SemiBold”, which really seems to have ideal proportions for subtitling IMO. Here is a very quick and dirty mockup showing Arial (current) on top, Noto Sans SemiCondensed Medium in the middle, and Noto Sans SemiCondensed SemiBold on the bottom. And no, that’s not even a real subtitle for what Han’s saying. You can click the image for a larger image.

The main differences are:

Stroke thickness. I find thicker subtitles (within reason) to be more readable, but it can have side-effects, such as seeming bigger and brighter at the same point size.
Letter width. Arial is a little wider than Noto SemiCondensed. I’m not sure it makes a difference readability-wise.
Color. To counteract the fact that thicker fonts appear brighter – sometimes too bright – at the same color as a thinner font, I’ve chosen to make the new fonts slightly dimmer (still effectively white unless you break out the Photoshop, we’re not talking about going back to the days of yellow DVD subs). You’ll see that the middle Noto font seems approximately the same brightness as the top, but the bottom seems much brighter. In fact, the bottom two are the same brightness, both slightly dimmer than the top.
Consistency between scripts. Right now we use a modernish utilitarian style for Latin/Cyrillic/Greek, but a more traditional style for Arabic and Thai. If we went all-in on Noto Sans, everything would be more stylistically similar.

Things to look for: the new subs might seem bigger and brighter–but I don’t want them to seem too big or bright. i.e. Would we need to back off the boldness and go back to medium weight? Reduce the brightness a bit more? Something else? Is there a better type of mockup which would be more useful?