Glossary
Experienced photographers may be familiar with traditional
fi lm-based terms and acronyms, many of which have their origins
in the disciplines of optics, chemistry, and physics. The language
of digital imaging has its roots in the fi elds of computing and
commercial printing and has shown itself to be remarkably
inventive in creating new buzzwords at the drop of a microchip.
Here’s a brief introduction to some of them that a digital pho-
tographer might fi nd useful.
AF Autofocus, automatic motorized focusing.
AI Focus AF In cameras such as Canon’s EOS-1D and
40D, this is an Autofocus mode that automatically switches from
One-Shot Autofocus to AI-Servo Autofocus when a subject
moves.
AI Servo AF Autofocus mode for moving subjects with focus
tracking and shutter priority.
Aliasing Sometimes when a graphic is displayed on a monitor,
you will see jagged edges around some objects. These extra
pixels surrounding hard edges—especially diagonal lines—are
caused by an effect called aliasing. Techniques that smooth out
these “jaggies” are called anti-aliasing.
Analog Information presented in continuous form, corre-
sponding to a representation of the “real world.” A traditional
photographic print is an analog form, but when this same image
is scanned and converted into digital form, it is made up of
bits.
Average metering Through-the-lens (TTL) metering that
takes into consideration the illumination over the entire image.
BIT Binary digit. Computers represent all data—including
photographs—using numbers or digits that are measured in
bits.
Bitmap Collection of tiny individual dots or pixels—one for
every point or dot on a computer screen.
BMP Often pronounced “bump,” it’s the fi lename extension
for a Windows-based bitmapped fi le format.
