Background estimation and subtraction is intimately related to science cases like source detection and measurement. I would like to understand how it is implemented in the stack, and how choices in configuration parameters impact the background model it gives. Following discussions from Alex Drlica-Wagner and Jim Bosch, a notebook that mimics the detection-background subtraction-detection-background subtraction iterative process in processCcd can be helpful in guiding users through inner workings of the stack and flesh out bg estimation.