def FWHMeff2FWHMgeom(FWHMeff):
    """
    Convert FWHMeff to FWHMgeom.
    This conversion was calculated by Bo Xin and Zeljko Ivezic (and will be in an update on the LSE-40 and overview papers).
    @param [in] FWHMeff (the single-gaussian equivalent FWHM value, appropriate for calcNeff) in arcseconds
    @param [out] FWHMgeom (the geometric FWHM value, as measured from a typical PSF profile) in arcseconds
    """
    FWHMgeom = 0.822 * FWHMeff + 0.052
    return FWHMgeom
