Datasheet

5
■ CHIPS AND PIXELS
JPEG is a file format that was developed to reduce file size by using mathemati-
cal algorithms that simplify the pixel structure in the bitmap image. This process is
considered lossy because some image detail is “lost” during the process. Digital cam-
eras apply a conservative level of compression or size reduction, and this is generally
considered visually lossless. This does not mean that there is no loss—just that the loss
is not apparent at first glance. Even the best JPEG file does not carry the same amount
of information or image detail as a noncompressed or unaltered version.
The main advantage to shooting JPEGs is that by compressing the file size, you
can fit many more images onto a memory card (so you don’t have to change cards as
often). Because the files are smaller, they also write faster and enable faster shooting
speeds. This can be important for shooting wedding candids, news, sporting events,
and any other fast-breaking action. The disadvantage to shooting JPEGs is that you
have to accept the camera’s interpretation—of color, contrast, etc.—and you limit the
potential quality of the image. You give up some flexibility and quality for speed and
convenience.
JPEG Compression Artifacts
JPEG compression works by simplifying adjacent tones; similar tones are assigned the same
value. This can cause distinctive “blocky” artifacts and “messy” edges, which are most notice-
able in extreme magnifications. JPEG artifacts can become a problem when image files are
sharpened for print output or scaled up from smaller sizes. For most work destined for offset
lithography (magazines and newspapers), JPEG artifacts don’t pose a problem because they
are obscured by the printing linescreen.
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