Pentax 645 645 Manual - Page 55

Programmed

AE

Diagram

The

Pentax

645's

shutter/aperture

combination

in

the

Programmed

AE

mode

is

shown

in

the

chart.

The

green

line

represents

the

variation

of

shutter

speed

and

aperture

combination

with

the

standard

75mm

f/2.8

lens

(w/ISO

100

film).

Note

that

only

the

shutter

speed

slows

down

after

the

lens

reaches

its

limit

of

f/2.8

in

combination

with

a

speed

of

approx.

1/60

sec.

Using

a

lens

with

a

different

maximum

aperture,

the

exposure

program

varies

the

aperture

and

the

shutter

speed

in

combination

until

reaching

the

maximum

aperture

of

the

lens

in

use.

For

example,

with

an

f/4

lens

the

program

adjusts

the

combination

as

shown

by

the

green

dotted

line.

When

using

a

lens

with

a

different

maximum/minimum

aperture,

or

film

with

a

different

ISO

film

speed,

refer

to

the

fine

green

and

dotted

green

l

ines

seen

in

the

Programmed

AE

diagram.

The

limit

of

the

meter

coupling

range

will

vary

if

a

lens

other

than

the

75mm

f/2.8

standard

lens

is

utilized.

Meter

Coupling

and

Shutter/Aperture

Coupling

Range

Meter

coupling

range

indicates

the

range

of

subject

luminance

within

which

the

built-in

exposure

meter

functions

to

control

exposure.

The

shutter/aperture

coupling

range

is

that

part

of

the

meter

coupling

range

within

which

the

shutter

speed

and

f/stop

can

be

combined

for

proper

exposure

control.

With

the

75mm

f/2.8

standard

lens

and

ISO

100

film,

the

meter

coupling

range

extends

from

EV

3

(f/2.8,

1

sec)

to

EV19

[f/22,

1/1000]

.

In

the

diagram

at

the

left,

the

diagonal

lines

from

the

left

top

to

lower

right

will

move

in

parallel

depending

on

the

ISO

rating.

The

diagram

within

the

frame

illustrates

the

meter

coupling

and

shutter/aperture

coupling

ranges.

EV

(Exposure

Value)

EV

represents

the

amount

of

exposure

by

a

combination

of

the

shutter

speed

and

lens

aperture,

determined

by

the

film

speed

and

the

brightness

of

the

subject.

53

Pentax 645 645 Manual - Page 55

Shutter/Aperture

Page 55 highlights