  The measurement of magnitudes with different filters in photometric surveys
gives access to cosmological distances and parameters. However, for current and
future large surveys like the ZTF, DES, HSC or LSST, the photometric
calibration uncertainties are almost comparable to statistical uncertainties in
the error budget of type Ia cosmology analysis, which limits our ability to use
type Ia supernovae for precision cosmology. The knowledge of the bandpasses of
the survey filters at the per-mill level can help reach the sub-percent
precision for magnitudes. We show how a misknowledge of the bandpasses central
wavelengths or of the presence of out-of-band leakages leads to biased
cosmological measurements. Then, we present how to measure the filter
throughputs at the required precision with a Collimated Beam Projector.
