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Re: [csswg-drafts] [css-fonts] Proposal to extend CSS font-optical-sizing (#4430)

From: arrowtype via GitHub <sysbot+gh@w3.org>
Date: Wed, 10 Jun 2020 22:09:01 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-642293376-1591826940-sysbot+gh@w3.org>
> they treat `1 CSS px = 1 physical pt`

Maybe someone else should also test this, but ... 

I don’t think that is even close to true on my Apple devices?

(Unless, perhaps, I am misunderstanding what you mean by “treat as equal.” I guess maybe there could be some kind of argument that a user tends to be closer to a laptop screen than to a printed page, and therefore treating as equal is attempting to match arc radians? Annecdotally, however, the opposite is true for me: I tend to read papers from maybe 16"–20" away, but I sit about 32" from my screen.)

Below is a photo comparing:

- [the same page](https://codepen.io/thundernixon/pen/ZEbVBrz) with 12px font-size on a MacBook Pro 16" at default scaling & 100% zoom and an iPhone XR at default scaling (with `initial-scale=1` in the `head`)
- the same text set in the same font at 12pt on macOS Pages at 100% zoom, and then printed out onto standard letter-size paper without scaling.

The rendered font size of text really is consistent between the 12px in Safari & 12pt in Pages (sorry, I didn’t properly match the line height, but I checked with a screen capture overlay). However, 12px on the iPhone is far smaller, and 12pt on a printed page is far larger.


Even if I scale up my MBP display to its largest setting, the 12px type is still quite a bit smaller than 12pt printed text.


The closest I can get to a screen:physical match is if I 1) scale to the second-largest screen setting and 2) set the CSS to 12pt. But, even then, the printed size is still slightly larger.

Just to be sure this wasn’t some weird inconsistency in my own font, I also tested it with Times New Roman. Again, the apps match 12px/12pt on the same screen, but the physical size of printed 12pt text is about double the physical size of text on screen.


Or, have I completely missed the point of what you and Myles meant?

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Received on Wednesday, 10 June 2020 22:09:03 UTC

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