What is ISO and Why Should I Care?

Most of us know that one of the keys to great photography is getting the right exposure and that ISO is a vital piece of the equation. But what is ISO, exactly? In the video below, Sareesh Sudhakaran explains all about ISO and why knowing your camera’s native ISO is so important:

The term ISO comes from the International Organization for Standardization (informally known as the International Standards Organization) and its ratings let camera users know how sensitive a sensor is at any given time. This sensitivity allows your sensor to pick up both light and color information from your subject. In low light situations, the sensitivity of the sensor will determine how much (if any) information is recorded. Selecting the proper ISO setting for any given shot ensures that you’ll get the best dynamic range and color performance possible out of your camera.

How you see pixels

Light enters the aperture and tells the pixel to activate.

Native ISO

“Every sensor is designed to operate best at one ISO.”

While most of us have heard that it’s best to shoot with the lowest ISO possible, that’s not always true with all cameras—especially video cameras. Every camera has a base or native ISO–its sweet spot–where each pixel produces the maximum dynamic range and color. For many still photography cameras, this ISO is 100. For many video cameras, however, the native ISO is higher. Shooting above (or below!) this native ISO can affect the quality of your images.

Lucky for us, most modern cameras have a native ISO range we can work from, not just a single setting. This number is the range of ISOs the camera can achieve without using any of the camera’s software. As a result, the results are so similar in photo quality to the native ISO that the differences in dynamic range and color performance are imperceptible. For example, the ideal Nikon D7000 range is from 100 to 6400. Anything above or below this will engage the camera’s software (it’s still shooting at 6400 but will over or under expose to compensate). This is when quality differences may begin to be perceptible. The farther away you are from this range, the more you’ll lose dynamic range and color quality. Finding your camera’s native ISO and range is pretty easy—it should be in your camera specifications.

The takeaway? Just because a camera allows you to raise ISO beyond its ideal range doesn’t mean you should. In fact, according to Sudhakaran, “there’s no instance where raising (or lowering) the ISO from its native ISO is good.” And while your photo needs may not be as absolute as that, knowing your camera sensor’s sweet spot can keep you in range of your best quality images.

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