Spectral reflectance of the dust, averaged over the northern ansa (red points), the whole disc (blue points) or the central part of the ring between 0.3′′ and 0.9′′ (green points). The black dotted line corresponds to the scaled flux of the A0V star HR 4796 A to show the transmission of the atmosphere and instrument in the IFS wavelength range. The IFS spectral resolution is 50. The uncertainty is given at a 3σ level.