Our old remote sensor here "sees" the picture on the wall through a two step process. First, the lense of his eyeball gathers radiation (i.e. light) information which has come from some external light source (a lamp, perhaps) and is then reflected off the picture through his eyeball lense and onto his retina. The eyeball-lens-retina arrangement remotely senses this radiation information. The brain is responsible for interpreting this information from nerve connections to the optic nerve, and leads to the human interpretation of the scene viewed.