What you need to know
- It works with aperture and shutter speed to determine the exposure of a picture.
- It can cause noise on the final image.
What it is
Ever wonder why you’re able to see so good at night? Your eye will cause your iris to open up your pupil. But once it gets too dark this won’t be enough. That’s why your retina was designed with rods and cones. The cones are great at seeing color when there’s plenty of light. The rods are extra sensitive though.
Remember our example of a garden hose being used to fill up the bucket. In this analogy choosing a different sized bucket is setting the ISO.
As ISO gets higher the sensor is more sensitive to light. Speed gets longer more light is let in and the more exposure the image is.
Typical values are 100, 200, 400, 800, 16000 etc…
In most circumstances you want to choose the lowest ISO you can for the light. That’s because as the sensor amplifies the light coming in to make it more sensitive it causes noise. This is very similar to the ISO grain effect from film.
Generally speaking ISO is a tool use to allow choose the Shutter Speed and Aperture you want.
The amount of noise created is dependent on the ISO chosen and you model camera. Generally speaking newer camera and larger sensors have less noise. It’s helpful to know what ISO noise starts appearing for your camera. For my Canon 60D it’s about 1600. For my Canon 6D its more like 12800.
Here’s someone else explaining this concept in a short video on ISO.
This article discusses how you can use this knowledge to get your pictures in focus.
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