Median Subtract

The Median Subtract command estimates the local background by computing a median-filtered version of the image and subtracting it from the original. The result retains only the features that differ from the local median — typically small bright objects on a smooth background.

When to use

Use Median Subtract as an alternative to Rolling Ball when the background variation is not gradual but is best captured by a local median.

Parameters

Parameter	Description
Radius	Radius of the median filter window in pixels

A larger radius estimates the background over a wider area. The radius should be larger than the largest object of interest so those objects do not distort the background estimate.