  Usually, important parameters of young, low-mass star clusters are very
difficult to obtain by means of photometry, especially when differential
reddening and/or binaries occur in large amounts. We present a semi-analytical
approach that, applied to the Hess diagram of a young star cluster, is able to
retrieve the values of mass, age, star-formation spread, distance modulus,
foreground and differential reddening, and binary fraction. The global
optimisation method known as adaptive simulated annealing (ASA) is used to
minimise the residuals between the observed and simulated Hess diagrams of a
star cluster. The simulations are realistic and take the most relevant
parameters of young clusters into account. Important features of the
simulations are: a normal (Gaussian) differential reddening distribution, a
time-decreasing star-formation rate, the unresolved binaries, and the smearing
effect produced by photometric uncertainties on Hess diagrams. Free parameters
are: cluster mass, age, distance modulus, star-formation spread, foreground and
differential reddening, and binary fraction.
