Canon EOS Rebel T1i Brosur - Halaman 17

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Floating System

Dust- and Water-Resistant

Construction

Typical lenses correct for optical aberrations

only at commonly used focusing distances. Not

Most L-Series EF

surprisingly, at other focusing distances, especially

telephoto lenses are

close range, aberrations can compromise image

highly dust- and

water-resistant thanks

TS-E 24mm f/3.5L Floating System

to rubber seals at the

Focal plane

switch panels, exterior

Closest

shooting

seams, drop-in filter

distance

compartments and

Floating

lens mounts. Moving

parts, such as the focusing ring and switches,

are also designed to help keep out environmental

contaminants, providing reliable performance

under harsh conditions.

Floating Effect

(TS-E 24mm f/3.5L)

TS-E Movements

Tilt Movements alter the angle of the plane of focus between the lens and focal plane, and Shift Movements move the lens's

optical axis in parallel.

Astigmatism

quality. Rather than using fixed spacings, Canon's

floating system dynamically varies the gap

between key lens elements based on focusing

distance. Most aberrations are effectively sup-

pressed throughout the focusing range, assuring

high image quality in all shooting situations.

Circular Aperture

Canon lenses featuring circular aperture diaphragms

Reverse tilt and shift greatly reduces the range on which focusing

employ curved blades to create a smoothly rounded

is possible.

opening as the lens is stopped down. As a result,

most out-of-focus background highlights are

rendered as natural-looking rounded shapes

rather than as distracting polygons. These lenses

deliver smooth, consistent stop-down action

(even at 10 fps), near-silent operation and

excellent optical characteristics.

Inner and Rear Focusing

An inner focusing lens has the focusing lens

The lens's tilt mechanism is used to achieve a pan focus effect

group(s) in front of the diaphragm, while a rear

that allows focusing all the way back.

focusing lens has the focusing lens group(s) behind

Tilt Movements –Using a normal lens, shallow or deep focus is

the diaphragm. Both designs allow for compact

controlled by the size of the aperture used to adjust depth-of-

optical systems that produce faster AF. And because

field. Canon TS-E lenses can help achieve this by the tilting of

the front of the lens does not rotate to focus, filter

the lens barrel in relationship to the focal and subject planes.

This allows for the appearance of extremely deep focus even at

orientation remains constant.

wide open apertures, and shallow focus at smaller apertures.

AF Stop Feature

Pressing the AF Stop button (featured on several

EF IS telephoto lenses) momentarily locks the AF

to help prevent the focus from shifting to a passing

obstruction. After the obstruction has cleared, the

focus will still be on the subject, and you can quickly

resume shooting. AF Stop buttons are positioned at

Using Tilt Movements to Focus an Oblique Subject Plane

four locations around the lens grip for easy access.

EF 24mm f/1.4L II USM •f/2.8 •1/30 sec.

Full-Time Manual Focusing

Canon EOS cameras with EF lenses deliver impec-

cable AF precision. Manual focusing capability,

nevertheless, can enhance flexibility. Canon EF

lenses with full-time manual focusing enable the

photographer to manually tweak focus without

switching out of AF mode. Since AF action does

not cause the focusing ring to turn, it can be made

wider for improved grip and comfort.

Shift was used to adjust the image to keep the building

perpendicular all the way to the top.

Without using shift causes the image of the building to lean in at

the top.

Shift Movements – By keeping the camera level, and

using the shift function to raise the lens instead, this per-

spective effect can be corrected. With the camera's focal

plane set parallel to the building, shifting the lens upward

will obtain a more rectangular-looking building.

Depth-of-field with tilt movements

Plane of optimum focus

Film plane

With a normal lens

Using Shift Movements to Focus Tall Building

–

EF 8

15mm f/4 Fisheye •f/4 •1024 sec.

–

EF 8

15mm f/4 Fisheye •f/5.6 •1/200 sec.

Specialty Lenses

Fisheye — With its unique focal length range,

the EF 8-15mm f/4L Fisheye USM is the world's

widest fisheye zoom lens. It delivers 180°

diagonal angle of view images for all EOS SLR

The diagram below shows the relationship between each

image size and a 180˚ angle of view for each focal length.

Focal Length: 8 mm

Approx. 10 mm

Full size

Circular fisheye

Full-frame fisheye

Approx. 12 mm

Approx. 15 mm

APS-H

Full-frame fisheye

*The red circle for each forcal length is the size of a 180˚ angle of

view on the image plane.

cameras with imaging formats ranging from full-

frame to APS-C, and provides 180° circular fisheye

images for full-frame EOS models. This new Canon

lens has a wide zoom range feature that provides

a truly elevated level of creativity and performance

for users shooting artistic compositions or

FOCAL LENGTH COMPARISON

15mm Fisheye

14mm

180°

114°

With a TS-E lens

85mm

100mm

28° 30'

24°

panoramic landscapes, as well as astronomy

and sports.

EF-S Lenses — Designed for the Canon EOS 7D,

EOS 60D and all EOS Rebel models with APS-C

sized sensors (with a 1.6x crop factor), Canon's

EF-S lenses take advantage of the sensor's smaller

size to help deliver optimized performance in

compact, lightweight designs. The EF-S 15–85mm

f/3.5-5.6 IS USM is a perfect example of this

technology. With a compact design, a 35mm

equivalent range of 24–136mm, and Optical

Image Stabilizer technology, it's a superlative

walk-around lens... possibly the only lens you'll

need to enjoy basic Canon digital SLR photography.

TS-E — TS-E lenses are capable of tilt and shift

movements, which bring 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 larger apertures;

shift movements slide the lens's optical axis along

the film/sensor plane, enabling photographers

to correct or alter perspective at almost any angle.

Macro — Canon's EF lens lineup has a number of

options for true close-up and macro photography.

APS-C

With five 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 is nearly

impossible for the unaided human eye to detect.

Full size

EF Mount

In designing the EF lens mount, Canon engineers

gave photographers a lot more than a way to quick-

ly attach a lens to a camera body. As the commu-

nication conduit between camera and lens, this

fully electronic mount system has none of the

shock, operational noise, abrasion, play, lubrica-

tion requirements, slow response, lever operation

17mm

20mm

24mm

28mm

104°

94°

84°

135mm

200mm

300mm

400mm

18°

12°

8° 15'

EF LENSES

limitations, or other design restrictions related

to mechanical linkage mechanisms. A self-test

system, using the lens's built-in microcomputer, can

even warn of malfunctions through the camera's

display. The EF mount makes possible high-speed

autofocus, precise aperture control and preview,

automatic compensation with lens extenders, and

both forward and backward compatibility with

new lens technologies—such as USM and IS—as

they are developed by Canon.

About Macro Magnification

A life-size macro lens—that is, a

1x magnification—records an

image on film at its actual size. If

you're photographing fruits, for

example, and it has a diameter of

1 in., it will occupy 1 in. of your

actual slide or negative. With a

digital SLR, at 1.0x magnifica-

0.25x

tion, the image projected onto

your camera's sensor will like-

wise be the same size at the sen-

sor plane as the actual subject

itself. Other macro lenses have

lower or higher magnifications.

A lens with 0.5x magnification

will produce an image on film

0.5x

that is half the size of the

actual subject. Your 1 in. fruit

then would only occupy 0.5 in.

on film.

In the other direction, a 5x

magnification lens will convert

the 1-in. fruit to a 5-in. diameter

1.0x

image. Since the entire image

won't fit in the frame of your

film, you will have an enlarged

image of a detail of the fruit.

Magnification is not the same as

focal length. A 50mm lens and a

180mm might both be macro

lenses with, for example, 1.0x

3.0x

magnification. The advantage of

the longer lens is that it allows

greater distance from a subject,

while allowing the same magnifi-

cation in the final image. The

180mm lens is ideal for shooting

tiny subjects without disturbing

them; the 50mm is better choice

5.0x

for copying flat documents.

35mm

50mm

70mm

75°

63°

46°

34°

500mm

600mm

1200mm

6° 10'

5°

4° 10'

2° 5'