Canon Digital Camera Lens System Manual - Seite 8

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CANON LENS TECHNOLOGY

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.

Image Stabilizer

Diffractive Optics

Canon's Image Stabilizer (IS)

Canon's use of diffractive optics

technology makes hand-held

result in lenses that are both

photography possible in more

high performance and more compact

low-light situations than ever before.

than those with traditional refractive

When camera shake occurs using

designs. While conventional glass lens

normal lenses without Image

elements disperse incoming light,

Stabilizer technology, the image

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.

with Image

Stabilizer OFF

Here's how it works: Diffractive

coatings are bonded to the rear

surface of one lens element and the

Image Stabilizer ON

front surface of another. These

elements are attached to each other

projected to the focal plane also

to form a single multi-layer diffractive

shakes, often resulting in blurred

images at shutter speeds less than

optics (DO).

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:

multi-layer DO element construction

A high-speed

1: No camera shake

The DO element's dispersion

microcomputer

Group 1

Group 2

built into the lens

characteristics are reversed when

(focusing

(Image

group)

stabilising

compared with conventional optics,

analyses electronic

group)

Film

making it possible to cancel chromatic

signals emitted by

Plane

Group 3 to 6

aberrations at each wavelength when

vibration-detecting

Object

conventional and DO elements are

2: Lens front shakes

gyro sensors

downward

combined. In addition to chromatic

and controls a

aberration correction, this technology

mechanism that

also results in smaller lenses, with no

moves the image

3: Image stabilising

group counteracting

stabilising lens

compromise in quality. For example,

downward camera

the EF 400mm f/4 DO IS USM lens is

group parallel to

shake

approximately 27% shorter and 36%

the focal plane,

Direction of

lighter in weight than a conventional

resulting in a

Group 2

Movement

400mm f/4 telephoto lens would be,

sharper image.

yet the quality of the resulting image

How the Image

This compensation

Stabilizer Works

is comparable with one that an

effectively adds up

L-series lens would produce.

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.

EF 400mm f/4 IS DO USM •f/4 •1/1250 sec.

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

Ultrasonic Motor

aberration, has been one of the great

challenges in the design of telephoto

In order to achieve critical autofocus,

lenses. L-series telephoto lenses like

the elements within a camera lens

the EF 70-200mm f/2.8L IS USM and

have to move quickly, quietly and

EF 300mm f/4.0L IS USM utilise

precisely. With this in mind, Canon

Canon's Ultra-low Dispersion glass to

developed the world's first lens-based

minimise this effect. The design of

Ultrasonic Motor (USM), which spins

UD glass provides outstanding

the lens motor with ultrasonic

contrast and

oscillation energy. Instead of a large,

sharpness and

noisy drive-train system, electronic

minimises the

vibrations created by piezoelectric

splitting of colours

ceramic elements power the

as they pass

mechanical action of the lens,

through the

elements, resulting in cleaner colour

Ring-type USM

throughout the image.

Micro USM

Gear unit

Even more effective at suppressing

chromatic aberration are Fluorite

Micro

USM II

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

EMD

glass elements, giving these L-series

various lens actuators

lenses their spectacular performance

and relatively compact design.

providing constant torque, with

virtually instantaneous stops and

starts. USM lenses are both faster

Comparison of optical characteristics

and quieter than conventional

between optical glass and Fluorite

motor-driven autofocus systems, and

draw minimal power from the camera,

draining far less critical battery power.

Canon makes two

types of Ultrasonic

Glass

lenses. Ring-type

Anomalous

dispersion

USM-equipped

lenses, found in

ring-type USM

large aperture and

super telephoto

designs, allow

Fluorite

manual focusing

without switching

fluorite and UD glass

micro USM

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.

Aspherical Elements

EF Mount

Wide-angle lenses and fast normal

focal-length lenses often suffer from

In designing the EF lens mount,

another optical problem; spherical

Canon engineers gave photographers

aberration. Spherical aberration

a lot more than simply a way to

occurs when the point of focus of the

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,

spherical aberration of

convergence of parallel

spherical lens

light rays by an

lubrication requirements, slow

Aspherical lens

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

spherical

even warn of malfunctions through

lens

the camera's LCD readout to help

example

ensure high reliability.

aspherical lens example

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

electronic mount -

is no sharp point of focus, the image

camera side

looks blurred. Canon's Aspherical

elements change the curvature from

The EF mount allows for high-speed

centre to edge, to align the points

focus, precise aperture control and

of focus of the incoming light rays so

preview, automatic compensation

that the entire image plane appears

with lens extenders, and forward

focused. Aspherical optics also help

compatibility with new lens

to correct curvilinear distortion as one

technologies like USM, IS and more,

would find in ultra-wide-angle

as they are developed by Canon.

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

Red

Coating and anti-reflective material

Blue

inside of lens barrels virtually

eliminate internal ghosting and flare

in all L-series lenses. Weather sealing

keeps dust out,

Red

and allows for

Blue

photography in

less-than-perfect

weather conditions.

Specialty Lenses

TS-E LENS MOVEMENTS

TS-E lenses are capable of tilt and

shift movements, which greatly

Canon's EF Lens system includes

expand picture-taking possibilities,

many special purpose lenses, ranging

bringing many of the advantages

from full-frame fisheye, Tilt Shift,

of technical view cameras to the

macro, and everything in between.

EOS system. Tilt movements alter

the angle of the plane of focus

FISHEYE

between the lens and film plane,

Perfect for super wide-angle and

making broad depth-of-field possible

special effect photography, Canon's

even at large apertures or vice versa;

full-frame fisheye can focus as

close as eight inches (0.2m),

shift movements move the lens's

optical axis in parallel, allowing the

and is tack-sharp throughout its

focus range. Up to three gel filters

photographer to change or correct

the perspective of their photograph

can be inserted into its built-in rear

filter holder.

at almost any angle.

EF 15mm f/2.8 Fisheye •f/16 •1/640 sec.

electronic mount -

MACRO

without Tilt

lens side

To bring small things into full-sized

Shift Lens

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

EF 100mm f/2.8 Macro USM •f/5.6 •1/6 sec.

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.

using shift movements to focus tall building

with Tilt Shift Lens

With a normal lens

With a TS-E lens