Having begun with bus tickets I end with a lavatory roll, or at least its central tube. This is my own optic, without mirror or lens. Use it in the manner of a spyglass, isolating the paintings in a gallery from frames or surrounding distractions. You will be amazed to share immediately the artist's viewpoint and vision. In a gallery light sources in pictures argue both with each other and the light source of the room itself. Homing in on a single view you cut out this visual noise. Space doubles: landscapes and still lifes come awake before your single eye. You are in effect bringing a portable camera oscura and pointing it back at a painting.
Try it on a Hockney.