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

From: Christoph Päper via GitHub <sysbot+gh@w3.org>
Date: Wed, 03 Jun 2020 05:37:03 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-637965330-1591162622-sysbot+gh@w3.org>
@nicksherman [CSS **1**](https://www.w3.org/TR/CSS1/#length-units): 

> Pixel units (…) are relative to the resolution of the canvas, i.e. most often a computer display. If the pixel density of the output device is very different from that of a typical computer display, the UA should rescale pixel values. The suggested _reference pixel_ is the visual angle of one pixel on a device with a pixel density of 90dpi and a distance from the reader of an arm's length. For a nominal arm's length of 28 inches, the visual angle is about 0.0227 degrees.

What was fixed retroactively is the relationship between physical and pixel lengths.

I always thought that 1 arc minute would make a nice unit, as it is the nominal optimum visual acuity. The reference pixel is about 1.362 arcmin or 1′22″. The mentioned 1 mm/m is about 3.44 arcmin. 

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Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4430#issuecomment-637965330 using your GitHub account
Received on Wednesday, 3 June 2020 05:37:06 UTC

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