How to avoid wide-lens backfacing camera on new phones?

[jan-ivar]

From a stackoverflow question, newer phones have multiple back cameras. How would an app distinguish between them, specifically: avoid or pick the often unsuitable wide-lens camera?

While getUserMedia does support device selection using constraints, I see no reliable difference in constrainable properties between a wide-lens camera and its regular counterpart.

Proposal: A new focalLength constraint.

This would be the distance between sensor and lens (I'm no photographer or device expert, but this seems to often be an inherent property of the lens, e.g. on the Samsung S10).

This would be different from the existing (and similar-sounding) focusDistance, which is distance from lens to object.