By understanding that an ISO 800 setting is three stops more sensitive than ISO 100, you now know that you can use a shutter speed that's three stops faster.
Let's say, with ISO 100 film, you're photographing a horse at twilight.
There's enough light to use an exposure of f/4 with a shutter speed of 1/15th of a second.
| ISO 100 | f/4 | 1/15th |
1/15th of a second is a slow shutter speed. The horse will be blurry from camera shake.
So, you switch to ISO 800.
Now you can use a faster shutter speed—three stops faster.
| ISO 100 | f/4 | 1/125th |
Here's how to count the number of stops in this example:
|
1/15th |
to |
1/30th |
is |
1 stop |
|
1/30th |
to |
1/60th |
is |
1 stop |
|
1/60th |
to |
1/125th |
is |
1 stop |
|
Total |
3 stops |
|||
The horse will be sharp—because you're able to use 1/125th instead of 1/15th.
Now, let's look at how Stop is spoken in the country called Lens Opening.
| Back | 14.7 | Next |