Absolute magnitude in the G band vs. G_BP  −  G_RP colour diagram, corrected for dust reddening, of the 496 798 high-quality sources in common between J-PLUS DR1 and Gaia DR2. The black dots are individual measurements. The coloured solid contours show density of objects, starting on 25 mag⁻² and increasing by a factor of ten in each step. We define three populations on this diagram: main sequence stars (465 583; white area), giant branch stars (30 922; grey area), and white dwarfs (293; blue area).