About 8 or 9 years ago I saw a self checkout pos provider demo a camera/screen system that would do basic images processing constantly to try and take pictures when people are clearly visible. A couple of low res, low colour palette, cropped images per user are much much easier to store. This was at a security conference.

Fair enough, sounds like a reasonable compromise, but I still question the entire premise of having these cameras in the first place, especially since they do not film the area where items are being handled. Tallying a loss of stock to a specific person would seem to be really quite difficult to do with only a set of photographs of the faces of everyone who utilised the self-checkouts within a certain period.