Re: <DKIM> Re: Pixels Per Inch needs to be standardized 🔍

nicolas.mailhot at nicolas.mailhot at
Wed May 4 20:04:53 UTC 2016

----- Mail original -----
De: "Jasper St. Pierre" 

> What are the dimensions of a projector, whose pixels-per-inch or
> dots-per-inch value is a distance of how far away the projector is for
> the wall, 

Please, not the projector strawman again.

Any perpendicular screen surface is trivial to handle, once you add the viewing distance to the mix. And those are 95% of the cases at least, and the only ones needing calibration in the first place.

Thus, for each screen:

1. detect kind of screen (projector, tv, set-top monitor, laptop screen, smartphone screen) → udev job via edid and other hardware hints

2. auto-set typical viewing distance (use THX or SMTPE recommandations for projectors, they're about the same anyway. It will just works for users that followed the recommandations, those with non-standard setup can do 3)

3. let the user and the app environment provide a more accurate value if they want (via sensors, user input, user lies, whatever). One distance value! One field or slider! No harder than the zoom slider DEs expose now, and a lot more universal (so user prefs need not be hardware-specific)

4. expose the resulted computed horizontal and vertical pixel angle for an eye at viewing distance of the center of the screen

5. let apps do smart things with the result

And you're done. Handles 100% of the sane cases of known screens, lets app people invent smart autozoom strategies, loads simpler than the colour calibration, that people actually do despite the hardships, more accurate than hardcoding magic values with no relationship with actual hardware.

Hell, even manufacturers of dumb analog amps have known for a long time it is not too hard to ask users for speaker distances, because consummers would rather input distance once, than have unbalanced sound (because speed-of-sound << speed-of-light, even small differences matter).

Why are we still arguing that computer UI is harder to do than analog amp UI ?

Nicolas Mailhot

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