Today’s Question: Is “native” ISO synonymous with “base” ISO? Is there only 1 “native” ISO?
Tim’s Quick Answer: No, native and base ISO are not necessarily the same thing. A native ISO is an actual amplification setting in the camera that does not require interpolation in processing. The base ISO is the lowest of the native ISO options.
More Detail: Digital cameras offer a wide variety of ISO settings. However, in many cases the options available are not truly “native” options. What that means is that the camera essentially doesn’t have all of the ISO settings you can choose from as built-in amplification options. Instead, the capture data needs to be interpolated to calculate pixel values for non-native ISO settings.
For example, you may be able to select an ISO setting of 160 on your camera. But chances are, the only native ISO settings in that range are 100 and 200. To calculate the pixel data for 160 ISO, the camera could expose based on 200 ISO and then interpolate the data to achieve a final exposure based on a 160 ISO setting.
In many cases a camera will offer native ISO settings in one-stop increments, such as 100, 200, 400, and so on. Values in between are generally non-native, being calculated based on interpolation.
The point is that a camera will generally offer multiple native ISO settings. The base ISO setting is simply (in most cases) the lowest of those native ISO options.