Advertisement
Film Speed Scales Compared
BSI and ASA
Logarithmic
Exposure Index
200 21
0
22
0
23"
24
0
25
0
26
0
27
0
28
0
29
0
30"
31
0
32
0
33
0
34
0
35
0
36
0
37"
ASA and BSI
Arithmetic
Exposure Index
8
10
12
16
20
25
32
40
50
64
80 100 125
160 200 250 320
400
European
Sche
iner
23
0
24
0
25
0
26
0
27
0
28
0
29"
300
31
0
320
33
0
34
0
35
0
36
0
37
0
38
0
39"
400
D IN
°/10
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Weston
Nos
.
6
8
10
12
16
20
24
32
40
50
64
80
100
125 160 200 250 320
Gen. Electric
10
12
16
20
24
32
40
48
64
80
100 125 160 200 250
320
400 500
European H & D
1300 1700 2100 2700
3500
4400
5600
7200 9100 11600
Relat
ive
Exposure
required
I
8.00 6.40
5.13
4.00 3.20 2.56 2.00 1.60
1.
28 1.00 0.80
0.64 0.50 0.40
0.32
0.25
0.20 0.16
Speed figures corresponding to the same film speed are listed underneath each other in the
vertical
co lumns.
The bottom
row
gives a comparison of the light requi red to expose films of d ifferent speeds. Thus a
26°
BSI film needs twice as
much
lig ht as one of
290
BS
I
(a
diffe rence of 3° BS
I).
In practice th is means:
34
Either open up the aperture by one stop, or use the
next s lowe
r
shutter speed
(double
the exposure ti me)
.
Advertisement
