IMAGINE HOLDING a magnifying glass before an object on the table, such as the letter, “B”, in the Budweiser label. While holding the line of site, and drawing the magnifier nearer to the eye, the “B” magnifies for a while, then explodes to white; promptly returning in reverse orientation and shrinking as you continue advancing the glass toward your eye.
The spot where it “explodes to white” is the plane of focus for this lens. This is where a plate in a camera would record a photographic image. However…
It is a strange place to be — in focus — because it is impossible to see anything.
Thwarticus 