After further work on jointcal, I've realized that the basic definition of PhotoCalib should be multiplicative-instFlux * zeroPoint(x,y, instead of the current division-instFlux * zeroPoint(x,y. Fortunately, PhotoCalib isn't really used in the stack yet, so now is the time to fix it. Minor changes will also be required in jointcal and meas_mosaic creation of a PhotoCalib for persistence.
This shouldn't have any impact on the existing API, just on the internal calculations and persistence.
Not RFCing this, as it was defined this way in the original RFC and we changed it during implementation, and all of the current stakeholders have agreed to the change (slack#dm).