After passing through the afocal system,
the image—whether enlarged or
shrunk—is still unfocused. That task is
the job of the last element in the zoom
lens: an unmoving, focusing lens. This
element has nothing to do with the size
of the image; it is not involved in zoom-
ing in or out. The final element focuses
the image so it hits the image sensor as
a sharp picture, whether it’s a close-up,
normal, or wide shot.5
The dance of the elements magnifies or diminishes the image. When the negative ele-
ment is closer to the front of the lens, the zoom is in telephoto mode. As the negative
lens nears the fixed, rear positive element, the afocal system turns the zoom into
wide-angle.4
CHAPTER 4 HOW LIGHT PLAYS TRICKS ON PERCEPTION^57