HOW YOUR CAMERA MAKES AN IMAGE
HOW YOUR CAMERA MAKES AN IMAGE
The preceding description might sound complicated. In reality, though, the process
an imaging chip employs to capture an image is even more complex.
First, the light coming through the lens is passed through several filters. These
include an infrared filter (some cameras use a very slight infrared filter, making
them ideal for infrared photography, , “Shooting”) and a
low pass filter, both of which help ensure better color and fewer artifacts. The image
is also blurred ever so slightly.
This last fact often causes some photographers to turn pale, particularly those
who have just spent lots of money on very sharp lenses. The blurring is there to help
in the demosaicing process. Even though an individual pixel is extremely small, it is
theoretically possible for a single pixel, or line of pixels, to be a separate color from
its surrounding pixels. This could confuse a demosaicing algorithm, so a slight blur is
applied so the colors of individual pixels are smeared ever so slightly into their
neighbors.
After you take a picture, the data is read off the image sensor, amplified, passed
through an analog-to-digital converter , and then passed to your camera’s
on-board processor. There, it is demosaiced to produce a color image. However,
straight demosaicing does not produce an accurate, attractive color image. A little
more calculation is required.
COMPLETE DIGITAL
PHOTOGRAPHY
FOURTH EDITION
BEN LONG
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