Variance plane - gen 3 - DECam

Paula · November 24, 2022, 2:31am

Hi all
I was wondering what is the algorithm/formula that creates the variance plane attached to the calibrated exposure? (calexp.variance.array) I haven’t been able to find the script/documentation where this step takes place.

Thanks.

timj · November 28, 2022, 5:49pm

A quick search suggests that it is calculated in isrTask:

github.com

lsst/ip_isr/blob/main/python/lsst/ip/isr/isrTask.py#L516-L521

      
        
            # Variance construction
            doVariance = pexConfig.Field(
                dtype=bool,
                doc="Calculate variance?",
                default=True
            )

@czw can point you at specific algorithms.