When you look around, the images that you see
are a result of light bouncing off of objects and
then entering your eyes. Cameras capture this
light in several ways. In the past, cameras
contained rolls of film on the inside. The film
contained chemicals which would react with light
and change color. When you took a picture, the
camera would let the light in for a short amount
of time. The chemicals in the film would react
with the incoming light and change color, with
brighter light causing the film to become darker.
This produced what was called a negative, a
reverse image of the picture that you took, where
bright sections of your picture are dark and dark
sections are bright.
To convert the negative image to the actual
photo, the negative was taken to a room, called a
darkroom. In the darkroom, light is made to shine
through the negative onto another sheet of paper
treated with chemicals, which react with the light
and produce the true image on the paper.
This process for taking pictures took a long
time to produce the final picture, so eventually
the Polaroid Corporation invented a camera which
combined all the chemical steps into the camera
and produced the picture immediately. These
cameras were called Polaroid cameras, or instant
Today, most cameras work in an entirely
different way. When you take a picture, light
enters the camera and hits a grid of thousands of
crystal photosites. Each photosite absorbs
the light energy, and converts it into an
electrical signal. This electrical information
corresponds to the brightness of light at that
part of the picture. The brightness information
from each photosite is then sent to an inkjet or
laser printer for printing.
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