Beecher's Handouts /

Language of Stop / 14.7 - Stop & ISO Example

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.