CHAPTER 4 HOW LIGHT PLAYS TRICKS ON PERCEPTION^59
The software built into the camera
compares each blank pixel with the
colored pixels nearest it. The soft-
ware runs the adjacent-color values
through a formula to determine
which color the blank pixel area
would most likely be if the picture
were a true zoom.3
The software fills the missing pixels with
colors based on its educated guess to pro-
duce an approximation of what an optical
zoom lens would have picked up.4
Spy in the Sky
In a common scene in movies and
television, a blurry photograph is
enlarged again and again until
the identity of the enemy spy is
revealed. That’s fiction. In reality,
only so much detail can be drawn
from a picture if the visual informa-
tion is not there to begin with. The
formulas, or algorithms, used by
a camera’s digital zoom or by
photo editing software vary in
their complexity and the speed
with which they can be computed.
They also vary in the results they
produce. Here are some compar-
isons between images shot with a
lens zoom and the common types
of software enlargements used for
digital zooms.