At one time, the dominance of the digital single-
lens reflex (SLR) camera seemed unassailable. It
gives the clearest, most precise view of the subject
with accurate feedback on focus. But the SLR has
lost ground to compact interchangeable lens
cameras using high-resolution electronic viewfinders.
Entry-level SLRs
The entry-level SLR is fully capable of professional
quality results but is built to offer many features at
low cost, using the APS-C or Four Thirds sensors.
These cameras will accept most, if not all, of the
lenses and accessories that can be used on larger
SLRs but are smaller, lighter, and generally offer
lower specifications than their professional
equivalents. Therefore, they make good back-ups to
professional gear. All current models offer HD video
recording in addition to a full range of stills settings.
Professional SLRs
There is no clear line between entry-level SLRs and
professional-level SLRs, as different models are
used by both amateurs and professionals. The larger
cameras—such as the EOS-1D series from Canon,
Some systems offer more than
50 interchangeable lenses.
Peppering of
buttons on camera
may take some
time to master.
Pentaprism cover conceals
a pop-up flash unit.
The most reliable, sturdy,
and consistent performance
can be expected from
todays SLR cameras. All the
technology used is highly
refined and all controls are
easy to access, allowing for
fluid, versatile photography
at professional levels for
affordable prices.
35mm film area
A camera lens projects a circular image. The sensor captures a
rectangular area centered on this image. If the rectangle extends
to the edge of the circle of light, the sensor captures the full field
of view. But if the capture area falls short of the edge, the field of
view is smaller. Many SLR cameras accept conventional 35mm
format lenses but use sensors that are smaller than the 35mm
format (around APS, or about 24 x 16mm). The result is that the
field of view is reduced, which in turn means the focal length is
effectively increased, usually by a factor of around 1.5x. This means
that a 100mm lens used on full-frame 35mm is effectively a
50mm lens when used with an APS-sized sensor. The convention is
to relate the actual focal length to the 35mm format equivalent.

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