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
image appears blurred because there is no sharp
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
large-curvature
lens elements that are mainly found
in wide-angle lenses, will significantly minimize
the occurrence of ghosting and flare caused by
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
anti-smear coating keeps soiling, smears and fin-
gerprints to a minimum for easy cleaning.
Focus Preset
Focus Preset enables you to program a focusing
distance in the camera’s memory. Normal picture
taking and focusing are unaffected by preset
distances. For example, at a soccer game, you
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.
with virtually instantaneous stops and starts.
USM lenses also draw minimal power from the
camera, ensuring longer battery life. Canon makes
two types of Ultrasonic Motor lenses. Ring-type
USM lenses, found in
large aperture and super-
telephoto designs, permit
manual focusing wit hout
first switching out of the
auto mode. Micro USM
designs bring the perform-
ance benefits of Canon’s
USM technology to a
wide assortment of
affordable EF lenses.
L-series Lenses
Most highly regarded among professional photog-
raphers, Canon L-series lenses are distinguished
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 –
like the EF 70-200mm f/2.8 IS II USM and EF
300mm f/4L IS USM – employ Canon’s Ultra-low
Dispersion glass to minimize this effect, providing
much improved contrast and sharpness. Even
more effective at suppressing chromatic aberration
are Fluorite elements, used in high-end super-tele-
photo L-series lenses. Composed of crystallized
calcium fluoride (CaF
2
), a single Fluorite element,
although costly, has roughly the corrective power
of two UD-glass elements, giving these L-series
lenses their spectacular performance and relatively
compact design.
33
32
Taken with EF 100-400mm f/4.5-5.6L IS USM
Diffractive Optics
Canon’s use of diffractive optics (DO) results in
high-performance lenses that are much smaller and
lighter than traditional designs. Canon’s unique
multilayer diffractive elements are constructed
by bonding diffractive coatings to the surfaces of
two or more lens elements. These elements are
then combined to form a single multilayer DO
element. Conventional glass lens elements disperse
incoming light, causing chromatic aberration.
The DO element’s dispersion characteristics are
designed to cancel chromatic aberrations at various
wavelengths when combined with conventional
glass optics. This technology results in smaller
lenses with no compromise in image quality.
Canon has also developed a new triple-layer type
DO lens that uses an advanced diffractive grating
to deliver excellent performance, with superb
control of color fringing. This configuration is ideal
for zoom lens optics and provides significant
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.
Ultrasonic Motor
Canon developed the world’s first lens-based
Ultrasonic Motor (USM) to power the lens autofocus
mechanism. Instead of large noisy drive trains
powered by conventional motors, Canon USM
lenses employ the minute electronic vibrations
created by piezoelectric ceramic elements. The
focusing action of the lens is fast and quiet,
Ring-type USM
Micro USM
Chromatic aberration canceled out
Chromatic aberrations reversed from
that of a refractive optical element
Image formation in the red, green and
blue wavelength order
Red
Green
Blue
Multi-Layer Diffractive Optical Element
Refractive Optical Element
and Multi-Layer Diffractive
Optical Element Combined
Refractive Optical Element
Image formation in the blue, green
and red wavelength order
Chromatic aberrations
EF 400mm f/4 IS DO USM •f/4 • 1/1250 sec.
Correction of Chromatic Abberation by the Multi-Layer
Diffractive Optical Element.
Comparison of optical characteristics between
optical glass and Fluorite
Glass
Red
Blue
Red
Blue
Fluorite
Anomalous
dispersion
EF LENSES
EF 24mm f/1.4L II USM
f/6.3 •13 sec.
Convergence of parallel light
rays by an Aspherical lens.
Spherical aberration
of spherical lens.
Optical Image Stabilizer Mode 2
and Mode 3
The standard settings of the Optical Image
Stabilizer are set so that it is most effective
when photographing stationary subjects. However
when panning with a moving subject is attempted
(tracking of the subject horizontally or vertically),
the shake-correction of the OIS may inadvertently
over-compensate and interfere with framing. To
help resolve this, Canon developed Optical
Image Stabilizer Mode 2. In this mode, if you
move the lens to follow a subject for a pre-
determined time, the Optical Image Stabilizer
does not correct for the intentional panning
while continuing to correct any camera shake
that’s perpendicular to the panning motion. The
result is a virtually smooth viewfinder image as
you follow the moving subject. Optical Image
Stabilizer Mode 3 activates IS only when the
shutter button is fully pressed, allowing for easy
panning of fast-moving subjects. Additionally,
Mode 3 gives the equivalent effect of a shutter
speed four stops faster, further positioning a
user for action photography.
Hybrid Image Stabilizer
During normal shooting situa-
tions, sudden camera move-
ment in rotational camera angle can cause
significant image blur. During macro or close-up
photography however, the image blur caused by
linear camera shake—when the camera moves
parallel to the subject—is more pronounced.
Optical Image Stabilizer is optimized to counteract
rotational or angular camera shake and works
well for most camera shooting situations. To
help compensate for linear camera shake, a new
acceleration sensor determines the amount of
shift-based camera movement. The new Canon
Hybrid Image Stabilizer technology employs a
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.
Linear Camera Shake