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There
are two major components of digital cameras that play a big part
in image quality – the image sensor and the lens. 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 determine 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 'normal'
lens is one that produces an image similar to what the human eye
sees. There is no standard length for a normal lens
because field of view is directly connected with the size of the
image sensor that captures the photo. 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 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 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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