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by voyou
5206 days ago
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You're right, and the article linked here is wrong. The CSS spec doesn't say that px is an angular measurement, and the formula given that is supposed to convert between px and radians has no basis in the spec. The spec specifically defines px as a length; angular measurements only become relevant in calculating the reference pixel, which is a length used to define the size of 1px in circumstances where physical pixels are significantly different in size from the physical pixels of a computer monitor. |
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> It is recommended that the reference pixel be the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the reader of an arm's length. For a nominal arm's length of 28 inches...
It would seem that the reference pixel is simply 1/2688 of the typical distance between your eyes and the device. If a device is meant to be used at half the "arm's length" distance (14 in), the reference pixel on that device would be only half as large. If a device is meant to be used at 3x times the distance (84 in), the reference pixel would be 3x larger. Much easier than angular diameters.