In order to identify the optimal imaging conditions for the highest contrast in biological tissue, we explored the optical contrast of a phantom as a function of depth and wavelengths of excitation. Our customized optical hardware featured a scanning microscope, and imaging spectrographs equipped with silicon and InGaAs CCD diode array detectors allowed directed comparison of the intensity of NIR (650-900 nm) and exNIR (1000-1600 nm) light transmitted through a phantom (milk). We demonstrated that the contrast depends on the phantom thickness and the wavelength. At low depths (less than 3 mm) NIR light provides the best contrast while exNIR light shows significantly higher contrast in phantoms thicker than 4.5 mm. Our results suggest that distinguishing biological features in deep tissue may benefit from the application of the exNIR for in vivo.