====== Before ISO, there is many other film speed system ======

  * https://en.wikipedia.org/wiki/Film_speed

| ISO | cam 2009- | ASA (1960-1987) | DIN (1961-2002) | GOST (1951-1986) |  apex (1960) |
| 25  |           | 25              | 15              | 22 | 3 |
| 32  |           | 32              | 16              | 32 |
| 50  |           | 50              | 18              | 45 | 4 |
| 64  |           | 64              | 19              | 65 |
| 100 |           | 100             | 21              | 90 | 5 |
| 200 |           | 200             | 24              | 180 | 6 |
| 400 |           | 400             | 27              | 350 | 7 |
| 800 |           | 800             | 30              | 700 | 8 |
| 1600 |          | 1600            | 33              | 1400 | 9 |
| 3200 |          | 3200            | 36              | 2800 | 10 |
| 6400 |          | 6400            | 39              | 5600 | 11 |
| 12500 | 12800  | 12500            |                 |      | 12 |
| 25000 | 25600 |  |                 |      | 13 |
| 50000 | 51200 |  |                 |      | 14 |
| 100000 | 102400 |  |                 |      | 15 |
| 200000 | 204800 |  |                 |      | 16 |
| 400000 | 409600 |  |                 |      | 17 |