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Re: [ambient-light] Security and Privacy considerations for ALS

From: Alexander Shalamov via GitHub <sysbot+gh@w3.org>
Date: Tue, 20 Jun 2017 15:20:56 +0000
To: public-device-apis-log@w3.org
Message-ID: <issue_comment.created-309793367-1497972054-sysbot+gh@w3.org>
> Source?

Maybe it was me :smile:. I did some research after I checked [light-level related discussions](https://github.com/w3c/ambient-light/pull/26#discussion_r113921653).

> As an aside, the note in the light-level section (copied below) is well worth a read (and might help either find alignment if some of the use cases match or, on the contrary, clarify that they're orthogonal concerns):

Note basically says, light-level is not mapped to real world lux values and should not be used (blindly) to e.g., adjust contrast of page because:

- Different schemes might be required for E-Ink and LCD displays
- Brightness of the screen is unknown
- Sensors might be inaccurate
- FOV of the sensor might be different from viewing angle of the screen

I [still think](https://bugs.chromium.org/p/chromium/issues/detail?id=642731#c25) it would be tricky to implement interoperable light-level feature that would work reliably for intended use-cases, e.g., to adjust contrast of the web page.

@lknik Thanks for spending your time to check the proposal.

> But indeed the lower values in lx are the most "informative", as you say.

Sorry, maybe I didn't explain properly. Values in a range of [0-50] might be useful to destinguish between dark environmental conditions, for example 'Full moon' vs 'Overcast sunset'. I'm not sure whether it would be big problem if we would loose sensitivity in that range. So, those values are not that informative.

I hope after origin trials we would get more information whether 'high precision' mode is required for ALS, then we can adjust accordingly, e.g., define permission policies based on precision of required data.

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