Notes. HR 8799 c absolute photometry from Marois et al. (2008). The relative photometry for the other planets is derived using two datasets (Sect. 2). For HR 8799 be, there is no clear bias between the two individual measurements and the error on the relative photometry is the average of the statistical errors of the individual measurements. For HR 8799 d, the error on the relative photometry is the quadratic combination of the statistical errors and of the bias (~0.08 mag). The statistical error on the individual measurements includes the fitting error and the stellar flux variations during the observation (1.1%, see text). The error bar on the absolute photometric values includes the uncertainty on the HR 8799 c absolute photometry.