Schematic representation of the evolution of GX 339-4 spectra during the rising phase hard state and HtS transition of an outburst. The dotted pink line indicates the RPh hard spectrum, the solid blue line corresponds to the RHS, and the dashed green line represents the HtS transition. The vertical black arrows indicate the transition sequence. Characteristic turnover frequency of each spectrum and the V filter frequency are shown with the vertical dashed lines. Characteristic spectral slopes in the ONIR and X-ray ranges are shown with α_ONIR and α_X.