An apparatus for and method of calculating an integrated index of a transparent, translucent or opaque material for a desired wavelength range, the method comprising measuring a filtered value of the material as a function of wavelength within the desired wavelength range and calculating a protection index from the measured filtered value. The integrated index is used to quantify the ultraviolet, infra-red, erythemal or aphakic exposure properties of the material. In addition, the integrated index is used to quantify the photopic and/or scotopic response capabilities of the material. Further, the integrated index is used to quantify the differential or mean color indices of the material in comparison to the color spectrum or another material. Moreover, the integrated index is used to quantify the heat flux absorbed by the material.