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FLD (“F” Low Dispersion) glass,
which has the highly desirable
anomalous dispersion characteristics
of fluorite. Careful arrangement
of these exclusive low-dispersion
glass elements gives Sigma lenses
superlative image rendition
untarnished by residual chromatic
aberration.
Sigma’s aspherical lens technology
contributes to outstanding
optical performance and compact
dimensions. These aspherical lens
elements compensate for the
spherical aberration and distortion
which cannot be completely
eliminated using conventional
spherical lens elements alone.
They are also key to reducing
the size and weight of high-power
zooms and other large lenses while
improving image quality. Sigma
has two kinds of aspherical lens
technologies. Hybrid aspherical
lens elements are made by forming
a polymer in an aspherical shape
on a glass lens surface. Glass mold
aspherical lens elements are made
by direct forming of the glass lens
material.
Sigma’s own Super Multi-Layer
Coating suppresses flare and
ghosting by preventing reflections
within the lens. All DG and DC
lenses in the current Sigma range
feature this original technology.
In digital cameras, flare and
ghosting may also be caused by
reflections between the image
sensor and lens surfaces. Here too,
Sigma’s Super Multi-Layer Coating
is highly effective, assuring images
of outstanding contrast.
SIGMA LENS TECHNOLOGY
Furthermore, since the front of the
lens does not rotate, polarizing filters
can be used with extra convenience.
The Hyper Sonic Motor (HSM) is an
original Sigma development that uses
ultrasonic waves to drive the auto-
focus mechanism. Its extremely quiet
operation helps avoid disturbing
photographic subjects. High torque
and speed assure rapid auto-focus
response. Sigma uses two types of
HSM: Ring HSM and Micro HSM.
The Ring HSM configuration permits
manual fine tuning of focus (manual
override) by turning a focusing ring
after auto-focus operation.
The polygonal shape of
a conventional iris diaphragm causes
out-of-focus light points to appear
polygonal. A rounded diaphragm is
designed to produce rounded out-
of-focus light points when opened to
near maximum aperture.
This creates attractive bokeh effects
in many situations, such as when
photographing a subject against an
out-of-focus surface of water from
which light is being reflected.
Sigma’s original Optical Stabilizer
(OS) technology uses two sensors
inside the lens to detect vertical
and horizontal motion.
By adjusting particular lens elements,
the OS compensates for detected
movement, thereby minimizing blur
caused by camera shake. This can
provide stabilization equivalent to
using a shutter speed four stops
faster. Since stabilization takes place
within the lens, what you see in the
viewfinder is the resulting stabilized
image. This lets you confidently
judge focus and composition.
Two OS modes are available,
depending on the lens.
Mode 1 detects and corrects vertical
and horizontal motion, ideal for
shooting with the camera in a fixed
position. Mode 2 detects and corrects
only vertical motion, making it ideal
for panning, as when shooting motor
sports, for example.
Camera shake correction mechanism OFF
Camera shake correction mechanism ON
This system adjusts the distance
between lens groups while focusing,
thereby reducing the amount of lens
movement required. The result is less
variation in aberration at different
shooting distances. Benefits are
particularly great in macro lenses
because they cover a wide range of
shooting distances, and in wide-angle
lenses which employ asymmetric
configurations of lens elements.
In a conventional lens, focusing
requires an extension of the entire
lens or the front lens group. However,
to better accommodate auto-
focusing mechanisms and close-
up photography, a need has arisen
for lenses that do not change their
length during focusing or suffer
from focus-dependent variation in
aberration. Therefore, Sigma has
developed focusing systems that
only move elements within the lens
barrel. These incorporate smaller and
lighter moving lens elements which
help improve auto-focus speed. With
their unchanging barrel length and
small variation in the center of gravity,
these lenses also enhance balance
and stability for the photographer.
The degree to which light is refracted
(bent) by glass depends on the
light’s wavelength (color). This fact
causes different colors of light to
focus at slightly different points.
The result is chromatic aberration,
the color fringing that is particularly
noticeable in telephoto lenses. Most
chromatic aberration can be removed
by combining a high-refractivity
convex lens element with a low-
refractivity concave element. But
residual chromatic aberration known
as “secondary spectrum” can only
be corrected with selected low-
dispersion glass materials.
In addition to ELD (Extraordinary Low
Dispersion) glass and SLD (Special
Low Dispersion) glass, Sigma uses
Exclusive low-dispersion glass
Original technology minimizes
secondary spectrum
Aspherical Lens
Effective correction of spherical
aberration and distortion
Sigma lens development is
dedicated to one thing: creating
great photographs. The key is
core technology research, which
lets us refine our advanced
processing and fabrication
technology, while finding
unconventional solutions to
optics challenges.
It is only when a lens can
deliver an excellent image
that you may appreciate
features of mechanical design
or control technology that
support operational comfort
and convenience. Technology
should be dedicated to ever
more faithfully capturing
precious moments and beautiful
scenes, with functionality
commensurate with this ability.
The scrupulous care with which
we approach all facets of
technology is reflected in the
extraordinary quality of each
and every Sigma lens.
Each of Sigma’s more than
40 lenses incorporates
original Sigma technology and
expertise gained from decades
of experience, guided by an
uncompromising philosophy.
Here we introduce Sigma's
technology, developed and
perfected to meet the varied
and sophisticated needs of
photographers while stimulating
fresh photographic creativity.
Each of Sigma’s more than
40 lenses incorporates original Sigma technology
and expertise gained from decades of experience,
guided by an uncompromising philosophy.
20mm F1.8 EX DG ASPHERICAL RF
Rear Focus System
Floating System
MACRO 50 mm F2.8 EX DG
28 mm F1.8 EX DG ASPHERICAL MACRO
Optical Stabilizer (OS)
Original Sigma technology
counteracts camera shake
Hyper Sonic Motor (HSM)
AF drive motor for rapid focusing
and quiet operation
Rounded Diaphragm
Designed to optimize bokeh
near maximum aperture
Inner and Rear Focus
Focus systems for optimized
performance
Floating System
Advanced focusing mechanism
reduces lens movement and
aberration variation
Super Multi-Layer Coating
Proprietary multi-layer coating
technology to virtually eliminate
ghosting and flare
SLD, ELD or FLD glass element
Ordinary glass
Small secondary spectrum
Large secondary spectrum
Chromatic Aberration Correction
APO 70-200mm F2.8 EX DG OS HSM
18-250mm F3.5-6.3 DC MACRO OS HSM
Inner Focus System
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