A method for the evaluation of target media parameters in the visible and near infrared is disclosed. The apparatus comprises a light source, an illuminator/collector, optional illumination wavelength selector, an optional light gating processor, an imager, detected wavelength selector, controller, analyzer and a display unit. The apparatus illuminates an in situ sample of the target media in the visible through near infrared spectral region using multiple wavelengths and gated light. The sample absorbs some of the light while a large portion of the light is diffusely scattered within the sample. Scattering disperses the light in all directions. A fraction of the deeply penetrating scattered light exits the sample and may be detected in an imaging fashion using wavelength selection and an optical imaging system. The method extends the dynamic range of the optical imager by extracting additional information from the detected light that is used to provide reconstructed contrast of smaller concentrations of chromophores. The light detected from tissue contains unique spectral information related to various components of the tissue. Using a reiterative calibration method, the acquired spectra and images are analyzed and displayed in near real time in such a manner as to characterize functional and structural information of the target tissue.