Random-phase extraction for FO calibrating Cepheids in the J-band. The red triangles show the differences between the mean magnitude based on the F3 template and on single-epoch NIR observations (top panel). The middle panel shows the residuals (green triangles) based on the G2 template, while the bottom panel shows the residuals (black triangles) of the single-epoch measurements. The shadowed areas shows the 2σ of the results (F7: light red; G2: light green; single-epoch: light gray), while the black lines display the mean.