Graphical explanation of distance and reddening determination method. The distance moduli (m − M)_λ, calculated from observed magnitudes and synthetic photometry in different bands, are plotted (black dots) as a function of their corresponding law coefficient, by which we define the applied extinction law. The slope and the intercept of the fitted line (solid black) are the values of E(B − V) and reddening-free distance modulus (m − M)₀, respectively. The (m − M)₀ level is shown in blue. Differences between (m − M)₀ and each (m − M)_λ represent extinction values A_λ in each band (in mag), and they are also labelled.