Section 1 The Basics
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Copyright Goodheart-Willcox Co., Inc.
Image Quality (Resolution/
Compression) Settings
Digital cameras can produce images at
different quality levels to meet particular
photographic needs. An image to be used in a
book or displayed as an 11″ × 14″ inkjet print has
different requirements from a 4″ × 6″ snapshot or
an image to be displayed on a web page.
The quality level for JPEG image files is
typically described as large, medium, or small,
and is based on the size of the output that can
be produced from that file. See Figure 2-17.
The definition of large, medium, and small,
in turn, depends on the camera’s resolution.
A large quality image from a 12Mp camera
is approximately 4000 × 3000 pixels and can
produce an excellent inkjet print approximately
9″ × 12″ in size. In contrast, a large quality print
from a 6Mp camera is approximately 3000 × 2000
pixels and can produce an excellent 7″ × 10″ print.
The medium and small sizes are relative to the
large size—for a 12Mp camera, a medium quality
would produce a 7″ × 10″ print, and a small
quality print would be 4″ × 5.5″.
Compression is the “squeezing” of an
electronic file to reduce its size. The size reduction
allows more images to be stored on a memory
card, faster copying from camera to computer,
and faster transmission via e-mail. Compression
of JPEG files is called lossy, since some image
data is discarded in processing. The amount of
discarded data affects image quality—the more a
file is compressed, the greater the data loss. The
amount of compression applied to an image file
can be selected from a camera menu.
Sophisticated cameras may offer the ability
to capture RAW images, Figure 2-18. These
images include all of the information captured
by the camera’s sensor and are not compressed
or processed in any way. With special computer
software, RAW images can be adjusted and then
converted to a conventional image file, such as
JPEG or TIF.
On-Board (Built-In) Flash
With the exception of high-end professional
models, virtually every camera available
today includes an on-board flash, Figure 2-19.
Jack Klasey/Goodheart-Willcox Publisher
Figure 2-16. Automatic white balance usually provides
good results, but some situations call for selecting one of
the other preset white balances from the camera’s menu.
Jack Klasey/Goodheart-Willcox Publisher
Figure 2-17. Relative sizes of high-quality prints that could be made from large, medium, and small JPEG files produced
by a 12Mp camera.