Canon EOS Rebel T2i Brochure page 16

Taken with EF 100-400mm f/4.5-5.6L IS USM
Optical Image Stabilizer Mode 2
panning of fast-moving subjects. Additionally,
and Mode 3
Mode 3 gives the equivalent effect of a shutter
The standard settings of the Optical Image speed four stops faster, further positioning a
Stabilizer are set so that it is most effective user for action photography.
when photographing stationary subjects. However
Hybrid Image Stabilizer
when panning with a moving subject is attempted
(tracking of the subject horizontally or vertically), During normal shooting situa-
the shake-correction of the OIS may inadvertently tions, sudden camera move-
over-compensate and interfere with framing. To ment in rotational camera angle can cause
help resolve this, Canon developed Optical significant image blur. During macro or close-up
Image Stabilizer Mode 2. In this mode, if you photography however, the image blur caused by
move the lens to follow a subject for a pre- linear camera shake—when the camera moves
determined time, the Optical Image Stabilizer parallel to the subject—is more pronounced.
does not correct for the intentional panning Optical Image Stabilizer is optimized to counteract
while continuing to correct any camera shake rotational or angular camera shake and works
that's perpendicular to the panning motion. The well for most camera shooting situations. To
result is a virtually smooth viewfinder image as help compensate for linear camera shake, a new
you follow the moving subject. Optical Image acceleration sensor determines the amount of
Stabilizer Mode 3 activates IS only when the shift-based camera movement. The new Canon
shutter button is fully pressed, allowing for easy Hybrid Image Stabilizer technology employs a
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Linear Camera Shake
highly sophisticated algorithm that combines
the feedback of both the acceleration sensor
and angular velocity sensor (found in current
OIS technology) and moves the image stabilizer
lens elements, effectively compensating for both
rotational and linear camera shake. Hybrid IS
dramatically enhances the effects of Optical
Image Stabilizer especially during macro shooting,
which may be difficult for conventional image
stabilization technologies.
Diffractive Optics
with virtually instantaneous stops and starts.
Canon's use of diffractive optics (DO) results in USM lenses also draw minimal power from the
high-performance lenses that are much smaller and camera, ensuring longer battery life. Canon makes
lighter than traditional designs. Canon's unique two types of Ultrasonic Motor lenses. Ring-type
multilayer diffractive elements are constructed USM lenses, found in
by bonding diffractive coatings to the surfaces of large aperture and super-
two or more lens elements. These elements are telephoto designs, permit
then combined to form a single multilayer DO manual focusing wit hout
element. Conventional glass lens elements disperse first switching out of the
incoming light, causing chromatic aberration. auto mode. Micro USM
The DO element's dispersion characteristics are designs bring the perform-
designed to cancel chromatic aberrations at various ance benefits of Canon's
wavelengths when combined with conventional USM technology to a
glass optics. This technology results in smaller wide assortment of
lenses with no compromise in image quality. affordable EF lenses.
Canon has also developed a new triple-layer type
L-series Lenses
DO lens that uses an advanced diffractive grating
to deliver excellent performance, with superb Most highly regarded among professional photog-
control of color fringing. This configuration is ideal raphers, Canon L-series lenses are distinguished
for zoom lens optics and provides significant by a bold red ring around the outer barrel. What
makes them truly distinctive, however, is their
remarkable optical performance — the result of
sophisticated Canon technologies, such as Ultra-
low Dispersion UD glass, Fluorite and Aspherical
elements and Super Spectra Coating.
Fluorite / UD Elements
Reducing color fringing, or chromatic aberration,
has been one of the great challenges in the design
of telephoto lenses. L-series telephoto lenses –
EF 400mm f/4 IS DO USM •f/4 • 1/1250 sec.
like the EF 70-200mm f/2.8 IS II USM and EF
Refractive Optical Element
300mm f/4L IS USM – employ Canon's Ultra-low
Chromatic aberrations
Refractive Optical Element
and Multi-Layer Diffractive Dispersion glass to minimize this effect, providing
Optical Element Combined
much improved contrast and sharpness. Even
Image formation in the blue, green
and red wavelength order
more effective at suppressing chromatic aberration
Multi-Layer Diffractive Optical Element
Chromatic aberrations reversed from
that of a refractive optical element
Chromatic aberration canceled out
Image formation in the red, green and
blue wavelength order
Red Green Blue
Correction of Chromatic Abberation by the Multi-Layer Anomalous
dispersion
Diffractive Optical Element.
reductions in size. A good example is the
EF 70-300mm f/4.5-5.6 DO IS USM lens, which
is 28 percent shorter than the EF 70-300mm
f/4-5.6 IS USM lens.
Comparison of optical characteristics between
Ultrasonic Motor
Canon developed the world's first lens-based are Fluorite elements, used in high-end super-tele-
Ultrasonic Motor (USM) to power the lens autofocus photo L-series lenses. Composed of crystallized
mechanism. Instead of large noisy drive trains calcium fluoride (CaF
powered by conventional motors, Canon USM although costly, has roughly the corrective power
lenses employ the minute electronic vibrations of two UD-glass elements, giving these L-series
created by piezoelectric ceramic elements. The lenses their spectacular performance and relatively
focusing action of the lens is fast and quiet, compact design.
EF LENSES
Aspherical Elements
Wide-angle lenses and fast normal-focal-length
lenses often suffer from spherical aberration.
When the light rays coming through the center
of the lens do not converge at the same point as
light rays coming through the lens edge, the
Ring-type USM
Spherical aberration Convergence of parallel light
of spherical lens. rays by an Aspherical lens.
image appears blurred because there is no sharp
Micro USM
point of focus. Canon's Aspherical elements use
a varying curved surface to ensure that the entire
image plane appears focused. Aspherical optics
also help to correct curvilinear distortion as one
might find in ultra wide-angle lenses. Canon
designs aspherical elements with extremely
precise variable curvature of one or both sides,
making possible lighter, more compact lenses.
Subwavelength and Fluorine
Anti-smear Coatings
The Subwavelength Coating (SWC) is a new
proprietary lens coating that helps control ghost
and flare to a
far greater
degree than
with earlier
coating tech-
nologies.
Utilizing SWC
technology on
EF 24mm f/1.4L II USM
f/6.3 •13 sec.
large-curvature
lens elements that are mainly found
in wide-angle lenses, will significantly minimize
Red
the occurrence of ghosting and flare caused by
Glass
Blue
reflected light in environments that have posed
problems. SWC is used on the latest Canon wide-
angle lens, EF 24mm f/1.4L II USM. The Fluorine
Red
anti-smear coating keeps soiling, smears and fin-
Blue
gerprints to a minimum for easy cleaning.
Fluorite
Focus Preset
optical glass and Fluorite
Focus Preset enables you to program a focusing
distance in the camera's memory. Normal picture
taking and focusing are unaffected by preset
), a single Fluorite element, distances. For example, at a soccer game, you
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Focus Preset the goal area. Shoot normally
elsewhere on the field, but once the action moves
toward the goal, the user can instantly return to
the preset distance by turning a ring on the lens.
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