Comment by ssl-3

It sees it poorly. IR is deliberately (though imperfectly) filtered in the optical path.

The dim purpleish glow from a remote that is seen through [many] digital cameras would be quite bright if this IR filter weren't in place.

It doesn't have to be that way, but it usually is that way anyway -- as a design intent.

Cameras used for surveillance, meanwhile, often lack these filters. They're designed with more of a focus on getting any kind of image at all, including when working with infrared illuminators in the absence of visible light. Some even have mechanical elements that move filters out of the optical path for night mode.

This differs tremendously in comparison to a camera that is designed to produce very beautiful visible-light photographs.

(This all conspires to mean that IR is kind of a non-starter for this sort of cell phone camera hack.)