Pentax 30465 Operation Manual - Page 17

Distance/light, Intensity, Guide, Numbers

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temperature than tungsten bulbs and can be used freely with daylight films in rooms lit by tungsten bulbs without producing a reddish cast. DISTANCE/LIGHT INTENSITY Brightness (light intensity) drops of as distance from the lighting source increases. As brightness drops off with the square of the distance from the light source to the subject, light intensity at a distance of 2 meters from the camera will only be 1/4 of the value it is a 1 meter. Thus, all else being equal, objects two meters from the camera will require four times the exposure as those 1 meter from the camera. LIGHT SOURCE 3' lm 6' 2m (DISTANCE) 1 1/4 (INTENSITY) ASA 25 32 64 100 125 160 200 400 800 1600 3200 m 10 G. No. 11 16 20 22 25 28 40 56 80 113 ft 30 33 48 60 66 75 84 120 168 240 339 GUIDE NUMBERS: The guide number is the measure of the brightness of the flash in relation to the subject distance. Guide numbers vary depending upon the ASA rating of the film being used. To calculate the guide number in meters, multiply the distance in meters by the f-number. For the guide number in feet, multiply the distance in feet by the f-number. Although all the practical exposure data needed for operating the AF 200S is provided on the control panel, manual guide numbers as well as some additional ASA speeds are listed above. 17

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temperature
than
tungsten
bulbs
and
can
be
used
freely
with
daylight
films
in
rooms
lit
by
tungsten
bulbs
without
producing
a
reddish
cast.
DISTANCE/LIGHT
INTENSITY
Brightness
(light
intensity)
drops
of
as
distance
from
the
lighting
source
increases.
As
brightness
drops
off
with
the
square
of
the
distance
from
the
light
source
to
the
subject,
light
intensity
at
ASA
25
32
64
100
m
10
11
16
20
G.
No.
30
33
48
60
ft
a
distance
of
2
meters
from
the
camera
will
only
be
1/4
of
the
value
it
is
a
1
meter.
Thus,
all
else
being
equal,
objects
two
meters
from
the
camera
will
require
four
times
the
exposure
as
those
1
meter
from
the
camera.
LIGHT
SOURCE
3'
lm
6'
2m
(DISTANCE)
1
1/4
(INTENSITY)
125
160
200
400
800
1600
3200
22
25
28
40
56
80
113
66
75
84
120
168
240
339
GUIDE
NUMBERS:
The
guide
number
is
the
measure
of
the
brightness
of
the
flash
in
relation
to
the
subject
distance.
Guide
numbers
vary
depending
upon
the
ASA
rating
of
the
film
being
used.
To
calculate
the
guide
number
in
meters,
multiply
the
distance
in
meters
by
the
f-number.
For
the
guide
number
in
feet,
multiply
the
distance
in
feet
by
the
f-number.
Although
all
the
practical
exposure
data
needed
for
operating
the
AF
200S
is
provided
on
the
control
panel,
manual
guide
numbers
as
well
as
some
additional
ASA
speeds
are
listed
above.
17