Reference Guide

ManualsBrandsCanon ManualsDigital CameraEOS 1

page

5

ELECTRONIC DATA COMMUNICATION

IN

THE

EOS SYSTEM

From

the

start,

the

EOS

system

was

designed

to

make

full

use

of

electronics

as

the

best

way

to

increase

its

functional

capabilities.

This

involved

some

major

commitments

at

the

design

level.

Among

them

was

the

concept

of

placing

intelligent

circuitry

in

each

component

of

the

system,

including

lenses,

accessory

backs,

and

flash

units.

Where

some

manufacturers

have

chosen

to

rely

on

ROM

(Read-Only

Memory)

chips

in

their

AF

lenses,

Canon

has

added

a

full-featured

microprocessor

including

RAM

(Random

Access

Memory)

that

is

used

to

control

the

built-in

focusing

motors

and

aperture

drive.

Similarly,

the

flash

microprocessor

controls

the

automatic

zoom

head

and

many

other

features.

By

distributing

the

computing

tasks

among

the

various

accessories,

functional

capabilities

are

increased.

Another

important

use

of

electronics

resulted

in

Custom

Function

Control

with

the

EOS

630

and

EOS-I.

The

photographer

can

tailor

basic

camera

operations

to

his

or

her

personal

preference.

This

type

of

control

was

never

available

in

previous

Canon

SLRs.

Finally,

the

increase

of

"clock

speed"

(the

rate

at

which

computation

is

carried

out)

has

produced

a

number

of

benefits.

The

most

obvious

of

these

is

far

quicker

AF

operation,

and

the

previously

impossible

Focus

Prediction

capability

now

built

into

the

EOS

630

and

EOS-I.

ELECTRONIC

FOCUS

PRESET

Selected

large-aperture

EF

telephoto

lenses--the

200mm

f/l.8L,

the

300mm

f/2.8L,

and

the

600mm

f/4.0L--have

a

focus

preset

function

that

can

"lock

in"

a

focus

setting.

The

photographer

can

focus

on

other

shots,

then

when

necessary

return

immediately

to

the

preset

focus

with

a

quick

turn

on

a

special

ring.

Focus

preset

works

in

manual

focusing

as

well

as

Autofocus,

so

it

can

be

used

at

all

times.

EVALUATIVE METERING

Evaluative

metering

differs

from

center-weighted,

partial

area,

or

spot

metering

by

analyzing

a

total

of

6

zones

which

cover

the

entire

picture

area.

The

luminance

(brightness

level)

of

each

zone

is

'

measured

and

the

resulting

data

is

"evaluated"

by

an

exclusive

algorithm

(mathematical

program)

which

sets

an

exposure

value

according

to

subject

size,

pattern,

and

contrast.

Particularly

useful

in

backlit

scenes,

evaluative

metering

is

equally

effective

in

horizontal

and

vertical

compositions.

It

can

be

used

in

any

exposure

mode

(except

Bulb)

with

any

EF

lens.

In

bright

light,

evaluative

metering

favors

highlights,

but

in

dim

light,

it

exposes

for

the

shadows.

In

the

'

EOS

630

and

the

EOS-I,

a

newer

algorithm

provides

improved

exposure

accuracy

with

transparency

films.