Optical sensors based on image acquisition hardware represent a promising technique to measure the chemical composition of an environment or the headspace generated by complex samples. However, this approach is still limited by the fact that only a restricted kind of interactions may change the visible spectrum of an indicator. As a consequence, the receptive field, namely the amount of different chemicals that can be captured by an opto-chemical sensor, is rather restricted. To extend the application of optical indicators we propose to use blends of porphyrins and acid-base indicators as materials for opto-chemical sensors. A suitable choice of the components allows to obtain sensing features that are not correlated to those of the single constituents. This strategy provides a straightforward method to develop sensor arrays for a wide number of practical applications, among them it is investigated here the measure of emissions from human skin.