Cumulative S/N calculated for an emission-line feature (Hα) from the integrated flux obtained by adding the spectra in the sorted order as shown in for the IFS observation of IRAS F06295-1735. High S/N spectra contribute to enhance the S/N of the integrated spectrum until the point at which the inclusion of additional (low-S/N) spectra does not contribute to increase the overall S/N of the integrated spectrum, creating either a plateau or a turn-off, marking the threshold value (range) sought for high quality spectra within an IFS cube (e.g. red vertical line).