Diagnostic parameters that we have used to select the sample of NGC 2298 stars with high-quality photometry. The parameters are plotted as a function of the instrumental m_F606W and m_F814W magnitudes. Red circles indicate the median rms_X, Y, and q_F606W,F814W per intervals of 0.4 mag. Red lines separate the well measured stars (thin points) from those that are more likely to have poorer photometry (thick points). See text for details.