Film Speeds Past and Present
The film speed rating currently in use is ISO (ISO125) which is in practical terms the same as ASA (125ASA), also given is the DIN rating following the ISO with / (ISO125/22°). Other recently used ratings are Weston and Scheiner, an earlier British rating was H&D. Russia had its own rating, Gost, which was only slightly different to ISO (ISO125 is 110Gost). Below is a table of the most used ratings.
ISO/ASA
400
320
250
200
160
125
100
80
64
50
40
32
25
20
16
12
Scheiner
38°
37°
36°
35°
34°
33°
32°
31°
30°
29°
28°
27°
26°
25°
24°
23°
Weston
320
250
200
160
125
100
80
64
48
40
32
24
20
16
12
10
DIN
27°
26°
25°
24°
23°
22°
21°
20°
19°
18°
17°
16°
15°
14°
13°
12°
H&D
13,000
10.000
8,000
6,400
5,000
4,000
3,200
2,500
2,000
1,600
1,300
1,000
800
640
500
400
GOST
360
280
220
180
140
110
90
70
56
45
35
28
22
18
14
11
Avo exposure meter, this gave readings in H&D (Hurter & Driffield), there were two
types, the standard for reflected light and the Avo - Smethurst High - Light which
was pointed at the sun or light source to take the Exposure reading.
