Evolution of the S/N (relative to its maximum) with the spectral resolution, for a fixed number of pixels (3300 pixels per spectrum here, corresponding to the case of HARMONI) and a correspondingly variable bandwidth. The largest spectral range is set to cover the H and K bands H (from 1 to 2.8 µm) for three different templates of planets signature. These maps include only the photon noise, not considering any wavelength-dependant instrumental transmission, which makes this result quite generic, informative of the planetary spectra properties and not of the instrument specificities. Three different planet temperatures are considered: 500 (left), 1200 (middle), and 1700 K (right).