Digital photography - Lenses
for Digital Cameras
The lens is
one of the components in digital cameras that
play a big part in image quality. Get the best you
can afford -- good quality lenses are essential for
getting the most out of digital photography.
Lenses are available in
various focal lengths which decide field of view and
depth of focus. As they become longer they can focus on
smaller areas but require more precise focusing to obtain
a sharp image. Longer lenses are also more susceptible to
movement and will likely blur images if the camera is
moved during a shot.
Long lenses are sometimes
called telephoto lenses. Because of their reduced field
of view, the images shot with telephoto lenses are
magnified compared with shorter lenses. Similarly,
shorter lenses give a wider field of view, so very short
lenses are called wide-angle lenses.
A 50mm lens is considered
normal for traditional 35mm cameras but digital image
sensors are much smaller than a frame of 35mm film, so
shorter lenses on digital cameras will capture the same
field of view as the 50mm lens on a 35mm camera. The
specifications of a digital camera lens will often
include a reference to how the focal length compares to a
35mm camera.
Almost every digital camera
has an optical zoom function that changes the focal
length of the lens. They are rated as a multiplier – a 3X
zoom will enlarge or reduce an image by 3 times from the
longest to the shortest setting.
Some cameras are also equipped
with a digital zoom. These work by cropping the image
digitally and then spreading the result over all the
photosites on the image sensor. This is inferior to
optical zoom and should not be used. Better results can
be obtained by editing the photo using computer
software.
Most digital cameras in the
mid-range and better have the ability to add lens
converters. These give you more options for digital
photography by allowing you to attach various types of
lenses and filters.
In addition, many digital
cameras can accept lenses made for film cameras. Because
of the difference in size between film and image sensors,
however, these lenses do not produce the same results as
with film cameras. A telephoto lens designed for film
will have a larger magnifying effect, and a wide angle
lens will have less effect on a digital
camera.
Lenses are quite expensive.
They should be kept in cases and covered with caps when
not in use. Most lenses come with caps but you may have
to buy extras in case they are lost. They are widely
available and fairly inexpensive.
Lens
hoods
Lens hoods are useful for
controlling the amount of light entering the lens. They
result in images that have less contrast – useful for
some outdoor situations.
Lens cleaning
kits
Lens cleaning kits are
available but should be used as infrequently as possible.
Avoid touching the lens with your fingers as the oils in
your skin can cause permanent damage to the lens coating.
Wipe fingerprints with a soft cloth but first remove dust
particles with a blower. Larger dust can be removed with
a soft brush.
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