Understanding ISO

       ISO

What is ISO?

ISO is the sensitivity to light. 

How does ISO work technically?

The lower the ISO, the less light is let into the camera. The higher the ISO, the more light is let into the camera. The lower ISO has faster shutter speeds while the higher ISO has slower shutter speeds.

How does ISO work visually in a photo?

When you lower the ISO it causes finer grain, but when the ISO is higher (closer to 6400), their will be "noise" in the photo. Such as grain in the background that wouldn't be seen in a 100 ISO photo.

Relationship to the exposure triangle

Whether or not you change the aperture for the photo, you need to change the shutter speed to balance the photo out. When you change the ISO it will effect the balance of the photograph, making you need to change the aperture and the shutter speed.