The DIN (Deutsche Industrie Norm) rating system for film speeds is based on a logarithmic scale where each increase by one represents one third of a stop. Most photographers are more familiar with the ASA system which doubles in number with an increase of one stop. However, the ISO rating system used today lists both, as in this example:
ISO 400/27°
The DIN rating comes second and is easily recognized by the degree symbol after it.
Here is a list of the DIN speeds matched with their ASA equivalents:
ASA DIN
3 6°
4 7°
5 8°
6 9°
8 10°
10 11°
12 12°
25 15°
32 16°
40 17°
50 18°
64 19°
80 20°
100 21°
125 22°
160 23°
200 24°
250 25°
320 26°
400 27°
500 28°
640-650 29°
800 30°
1000 31°
1200-1250 32°
1600 33°
3200 36°
6400 39°
12500 42°