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aspherical lens complex allows freedom of design, improved
performance, a reduced number of component lenses and
a compact size. |
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This
lens provides high optical performance while maintaining
a compact size. For example, the 12-24 mm F4.5-5.6 EX
DG ASPHERICAL lens widens the range of wide-angle lenses,
and it provides distortion-free images with image reproduction
performance equivalent to that of a single focal length
lens. Aspherical lenses allow the production of high-quality
images from compact, lightweight telephoto zoom lenses.
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| OS
(Optical Stabilizer) Function |
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function utilizes a built-in mechanism that compensates
for camera shake. It dramatically expands photographic
possibilities by alleviating camera movement when shooting
by hand held camera. |
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Developed
with Sigma's own technology, the OS (Optical Stabilizer)
function uses two sensors inside the lens to detect both
vertical and horizontal movement of the camera. This function,
which works by moving an optical image stabilizing lens
group, to effectively compensate for camera shake, helps
to set our lenses apart from the rest. To handle all types
of shooting conditions, the system has two optical stabilizer
modes. Mode 1 determines camera shake in vertical and
horizontal panning and compensates for image blurring.
It is therefore effective for taking general photography
or for shooting landscapes and other static subjects.
Mode 2 detects vertical camera shake and compensates for
blurring. It is effective for panning the camera to photograph
moving subjects such as motor sports.
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| This
lens uses a motor driven by ultrasonic waves to provide
a quiet, highspeed AF. |
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| To
ensure stability in focusing, this lens moves the inner
lens group or groups without changing the lens' physical
length. |
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| This
lens is equipped with a system that moves the rear lens
group for highspeed , silent focusing. |
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| Conventional
focusing has normally been performed by moving either
all lens groups as a fixed unit or only the first lens
group. AF cameras are now widely used, even for close-up
photography. Consequently, demand has arisen for a focusing
system that will keep the length of the lens unchanged
while showing little fluctuation of aberration. In response
to this demand, SIGMA has developed a new inner focus
system that moves two lens groups inside the telephoto
and telephoto MACRO lenses. This system has floating elements
that substantially improve the close-up capability of
the lens. The super wide angle lens having a large front-lens
uses a rear focusing system to move the rear-lens apparatus
and enhance the floating effect, and the18-125 mm F3.5-
5.6 DC lens uses an inner focusing system to move the
secondary lens apparatus. SIGMA has also succeeded in
attaining a minimum shooting distance of 19.7 inches/0.5
m throughout the entire zoom range of this lens. The rear
focus system ensures high-speed focusing with the APO
135-400 mm F4.5-5.6 RF and APO 170-500 mm F5-6.3 RF telephoto
zoom lenses. |
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 Although
telephoto zoom lenses can be used closer to the object
than single-focal length telephotolenses, there is still
a minimum shooting distance. SIGMA has made this minimum
distance smaller and developed the zoom MACRO lens for
taking close-up photographs of the same quality as those
taken with a regular MACRO lens, while maintaining the
performance specific to an APO lens. Rather than carrying
around the cumbersome accessories required for close-up
work, the photographer can now take photographs at amagnification
of 1:2 (one half lifesize) using a telephoto lens, by
quickly shifting from the normal setting to the full macro
setting. |
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| In
order to attain the highest quality images, the APO lens
has been made using special low-dispersion (SLD) glass
and is designed to minimize color aberration. |
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| SIGMA's
APO zoom lenses minimize color aberration. As the refractive
index of glass depends on the wavelength of light, color
aberration occurs when different colors form images at
different points. This problem often occurs with telephoto
lenses, but the Special Low-Dispersion (SLD) glass and
Extraordinary Low Dispersion (ELD) used in SIGMA's APO
lenses helps to compensate for color aberration, thereby
allowing them to produce of sharp images. |
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| Conv
(APO Teleconverter EX) |
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This
lens can be used with the APO Teleconverter EX. It can
increase the focal length and will interface with the
camera's AE (automatic exposure) function.
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The
exterior of this lens is EX-finished to denote the superior
build and optical quality, and to enhance its appearance.
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These
are large-aperture lenses with wide angles and short minimum
focusing distances. With an abundance of peripheral illumination,
they are ideal lenses for Digital SLR Cameras whilst retaining
suitability for traditional 35mm SLRs.
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| These
are special lenses designed so that the image circle matches
the smaller size of the image sensor of most digital SLR
cameras. Their specialized design gives these lenses the
ideal properties for digital cameras, the compact and
lightweight construction is an added bonus! |
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 SIGMA's
tele-macro mechanism lets you select a magnification of
up to 1:2 at the telephoto end simply by engaging a switch.
With a minimum shooting distance of 19.7 inches (50 cm)
over the entire zoom range, turning on the Macro switch
at the telephoto end allows the focus ring to enter the
macro range,allowing close-up photography. Since close-up
photography with a magnification of up to 1:2 is possible
without attaching a close-up lens or changing to a macro
lens, this mechanism gives you extra versatility in photography.
When the Macro switch is engaged, the zoom control ring
is fixed at the telephoto end. |
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| The
floating system is used to control the focus. This system
moves the different lens groups in the optical system
to different positions, thereby minimizing the telescoping
distance and the fluctuation of aberration at different
shooting distances. This system is particularly effective
for macro lenses (which encompass a wide range of shooting
distances) and wide angle lenses (for Single-Lens Reflex
cameras) whose lens composition is asymmetric. SIGMA uses
the floating system for the MACRO 50 mm F2.8EX DG lens
and the large-aperture wide-angle 28 mm F1.8 EX DG ASPHERICAL
MACRO lenses. |
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| The
DF (Dual Focus) system disengages the linkage between
the internal focusing mechanism and outer focusing ring
when the focusing ring is moved to the AF position. This
system provides easy and precise handling of the lens,
since the focusing ring does not rotate during autofocusing.
The wide focusing ring also enables easy and accurate
manual focusing. |
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