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Microsoft Picture It! Companion Guide
11
Chapter 2: Making the Most of Your Camera
Compression
You’ve seen one way to reduce photo file size: lower the resolution at which
you shoot the photo. You can also reduce file size by having the camera
compress the photo file as it saves the file to the camera’s memory. Compres-
sion consolidates similar information in the photo, and discards some informa-
tion. With JPEG compression, for example, series of similarly colored pixels
are grouped together and considered to be the same color. In the code that
makes up the file, the color information for these grouped pixels only has to be
listed once instead of hundreds, or even thousands, of times. This shortcut can
reduce file size considerably. Taken to extremes, a photo in highly compressed
JPEG format might be 95 percent smaller than the same photo in an
uncompressed format.
Although compression does reduce file size, it also reduces photo quality.
Slight to moderate compression might not noticeably reduce photo quality, but
high compression produces visible areas of splotchy color called artifacts. Even
with slight compression, artifacts become more pronounced each time the
photo is saved and compression is applied.
The left photo has been saved with lossless compression, so all of the image quality is
retained. The photo on the right was saved with heavy JPEG compression—which is not
lossless—and the compression significantly reduced the image quality.
File size and
photo quality
Lowering resolution
and increasing
compression both
reduce file size and
photo quality. Bearing
this in mind, you can
use file size as a rough
way to judge photo
quality.