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Aspherical Elements
Wide-angle lenses and fast normal
focal-length lenses often suffer from
another optical problem; spherical
aberration. Spherical aberration
occurs when the point of focus of the
light ray coming through the centre of
the lens does not align with the point
of focus of the light ray coming
through the lens edge. Since there
is no sharp point of focus, the image
looks blurred. Canon’s Aspherical
elements change the curvature from
centre to edge, to
align the points
of focus of the incoming
light rays so
that the entire image plane appears
focused. Aspherical optics also help
to correct curvilinear distortion as one
would find in ultra-wide-angle
lenses. Finally, Aspherical elements
have
an extremely precise variable
curvature of one or both sides,
allowing for more compact and lighter
lens designs.
Canon’s exclusive Super Spectra
Coating
and anti-reflective material
inside of lens barrels virtually
eliminate internal ghosting and flare
in all L-series lenses. Weather sealing
keeps dust out,
and allows for
photography in
less-than-perfect
weather conditions.
EF Mount
In designing the EF lens mount,
Canon engineers gave photographers
a lot more than simply a way to
quickly attach an interchangeable
lens to a camera body. As the
communication conduit between
camera and lens, the fully electronic
mount system has none of the shock,
operational noise, abrasion, play,
lubrication requirements, slow
response, or diminished precision
caused by lever operation, or design
restrictions related to linkage
mechanisms used to transfer data. A
lens operation self-test system, using
the lens’s built-in microcomputer, can
even warn of malfunctions through
the camera’s LCD readout to help
ensure high reliability.
The EF mount allows for high-speed
focus, precise aperture control and
preview, automatic compensation
with lens extenders, and forward
compatibility with new lens
technologies like USM, IS and more,
as they are developed by Canon.
Specialty Lenses
Canon’s EF Lens system includes
many special purpose lenses, ranging
from full-frame fisheye, Tilt Shift,
macro, and everything in between.
FISHEYE
Perfect for super wide-angle and
special effect photography, Canon’s
full-frame fisheye can focus as
close as eight inches (0.2m),
and is tack-sharp throughout its
focus range. Up to three gel filters
can be inserted into its built-in rear
filter holder.
MACRO
To bring small things into full-sized
view, Canon’s EF lens lineup has a
number of options for true close-up
and macro photography. With four
macro lenses for precision, and three
screw-on Close-up Lenses for
convenience, in addition to Life-Size
Converter EF and two Extension
Tubes, Canon’s macro lenses and
close-up accessories can uncover
detail that would be impossible to
detect by the eye and give new
perspective to extremely minute
subjects such as insects or the petals
of a small flower.
TS-E LENS MOVEMENTS
TS-E lenses are capable of tilt and
shift movements, which greatly
expand picture-taking possibilities,
bringing many of the advantages
of technical view cameras to the
EOS system. Tilt movements alter
the angle of the plane of focus
between the lens and film plane,
making broad depth-of-field possible
even at large apertures or vice versa;
shift movements move the lens’s
optical axis in parallel, allowing the
photographer to change or correct
the perspective of their photograph
at almost any angle.
Image Stabilizer
Canon’s Image Stabilizer (IS)
technology
makes hand-held
photography possible in more
low-light situations than ever before.
When camera shake occurs using
normal lenses without Image
Stabilizer technology, the image
projected
to the focal plane also
shakes, often resulting in blurred
images at shutter speeds less than
1/focal length. When this same
movement occurs with an IS lens
attached, a special group of lens
elements automatically shifts its
position, thereby compensating for
the shake and stabilising the image.
Here’s how Canon’s original Image
Stabilizer technology works:
A high-speed
microcomputer
built into the lens
analyses electronic
signals emitted by
vibration-detecting
gyro sensors
and controls a
mechanism that
moves the image
stabilising lens
group
parallel to
the focal
plane,
resulting in a
sharper image.
This compensation
effectively adds up
to three shutter speed steps to your
hand-held shooting capability,
depending on the IS lens you choose.
Canon’s IS lenses are perfect for low
light, or situations where a tripod is
not convenient.
Diffractive Optics
Canon’s use of diffractive optics
result in lenses that are both
high performance and more compact
than those with
traditional refractive
designs. While
conventional glass lens
elements
disperse incoming light,
thereby causing
chromatic aberration,
Canon’s unique multi-layer diffractive
elements work together with
conventional glass optics to cancel
the effects of dispersion and minimise
or eliminate chromatic aberration.
Here’s how it works: Diffractive
coatings are bonded to the rear
surface of one lens element and the
front surface of another. These
elements are attached to each other
to form a single multi-layer diffractive
optics (DO).
The DO element’s dispersion
characteristics are reversed when
compared with conventional optics,
making it possible to cancel chromatic
aberrations at each wavelength when
conventional and DO elements are
combined. In addition to chromatic
aberration correction, this
technology
also results in smaller lenses,
with no
compromise in quality. For example,
the EF 400mm f/4 DO IS USM lens is
approximately 27% shorter and 36%
lighter in weight than a conventional
400mm f/4 telephoto lens
would be,
yet the quality of the resulting
image
is comparable with one that an
L-series lens would produce.
Ultrasonic Motor
In order to achieve critical autofocus,
the elements within a camera lens
have to move quickly, quietly and
precisely. With this in mind, Canon
developed the world’s first lens-based
Ultrasonic Motor (USM), which spins
the lens motor with ultrasonic
oscillation energy. Instead of a large,
noisy drive-train system, electronic
vibrations created by piezoelectric
ceramic elements power the
mechanical action of the lens,
providing constant torque, with
virtually instantaneous stops and
starts. USM lenses are both faster
and quieter than conventional
motor-driven autofocus systems, and
draw minimal power from the camera,
draining far less critical battery power.
Canon makes two
types of Ultrasonic
lenses. Ring-type
USM-equipped
lenses, found in
large aperture and
super telephoto
designs, allow
manual focusing
without switching
out of the auto
mode. Micro USM designs bring
the performance benefits of Canon’s
USM technology to a wide assortment
of affordable EF lenses.
L-Series Lenses
No lenses have a better reputation
among professional photographers
than those in Canon’s L-series.
Identifiable by a bold red ring around
the outer barrel, these lenses are
distinctive in their performance
through use of optical
technologies like
Ultra-low Dispersion
UD glass, Fluorite
and Aspherical
elements and Super
Spectra Coating.
FLUORITE/UD ELEMENTS
Avoiding colour 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/2.8L IS USM and
EF 300mm f/4.0L IS USM utilise
Canon’s
Ultra-low Dispersion glass to
minimise
this effect. The design of
UD glass pro
vides outstanding
contrast and
sharpness and
minimises the
splitting
of colours
as they pass
through the
elements, resulting in cleaner colour
throughout the image.
Even more effective at suppressing
chromatic aberration are Fluorite
elements, used in high-end super-
telephoto lenses like the EF 300mm
f/2.8L IS USM and EF 400mm f/2.8L
IS USM. A single Fluorite element
has the corrective power of two UD
glass elements, giving these L-series
lenses their spectacular performance
and relatively compact design.
CANON LENS TECHNOLOGY
1: No camera shake
2: Lens front shakes
downward
3: Image stabilising
group counteracting
downward camera
shake
Group 1
(focusing
group)
Group 2
(Image
stabilising
group)
To
Object
Film
Plane
Direction of
Group 2
Movement
Group 3 to 6
ring-type USM
micro USM
fluorite and UD glass
Glass
Fluorite
Anomalous
dispersion
Red
Blue
Comparison of optical characteristics
between optical glass and Fluorite
EF 15mm f/2.8 Fisheye •f/16 •1/640 sec.
without Tilt
Shift Lens
with Tilt Shift Lens
With a normal lens
With a TS-E lens
Red
Blue
EF 100mm f/2.8 Macro USM •f/5.6 •1/6 sec.
Ring-type USM
Micro USM
Gear unit
Micro
USM II
EMD
electronic mount -
camera side
electronic mount -
lens side
spherical aberration of
spherical lens
convergence of parallel
light rays by an
Aspherical lens
various lens actuators
using shift movements to focus tall building
aspherical lens example
spherical
lens
example
Canon EF Lens: The Heart of the EOS System
At the core of the EOS system, Canon’s renowned EF lens series offers infinite
choices
and features for any project, and any budget. With over 50 lenses
ranging from fisheye to super-telephoto, with both fixed-length and zoom
lenses to fit any photographer’s needs, EF lenses have proven their worth in
every photographic context.
Canon designs and manufactures each of their lenses to provide high image
quality throughout the entire image area, with natural background blur, and
consistent colour regardless of the lens chosen. All Canon EF lenses are
designed to be quick, quiet, and highly reliable. With these priorities in mind,
Canon’s designs have remained on the cutting edge of technological
innovation – if a technology does not exist, Canon invents it. Here’s a closer look
at some of the technologies that Canon has incorporated into their EF lenses.
multi-layer DO element construction
How the Image
Stabilizer Works
EF 400mm f/4 IS DO USM •f/4 •1/1250 sec.
Image Stabilizer ON
with Image
Stabilizer OFF
1514
EOS CAMERAS
EF LENSES SPEEDLITES POWER SUPPLIES
DIGITAL
ACCESSORIES
SHOOTING
ACCESSORIES
PERIPHERALS
CASES AND STRAPS
EF LENSES
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