In the process of comparing HSC vs. LSST stack single-frame processing runs, we have been running with the Brighter-Fatter correction (BFC) turned off. The reason for this to begin with was that is was not yet available on the LSST stack when we started these comparisons. We also want to isolate as many features as possible in order to confidently assess their individual effects The functionality was ported on
DM-4837 with a default of doBrighterFatter=False. This issue is to continue the single-visit run comparisons (see e.g. DM-5301, DM-6490, DM-6491) with BFC turned on on both stacks.
In particular, we are finding that slight differences in the reference stars selected for a given CCD can result in significantly different psf models. Also, it was noted in
DM-4960 that LSST seems to select reference stars to a brighter cutoff than HSC. If a given field has a larger fraction of bright stars considered in the psf modeling, it is conceivable that it will be more significantly influenced by the BF effect, thus causing the large CCD-to-CCD variations seen in, e.g. DM-6490 (https://jira.lsstcorp.org/secure/attachment/28213/compareVisit-v1322-diff_base_PsfFlux-skyZp.png).