Either filter transmittance, filter reflectance or a combination of transmittance and reflectance is measured. Intact samples can be imaged in transmittance or diffuse reflectance. The tape was advanced and its gray coloration measured optically by either transmittance or reflectance. Leaf light reflectance goes up and leaf light transmittance goes down. The MPF is roughly the inverse of the transmittance at a given wavelength. This allows glass to block mainly short-wave infrared radiation without greatly reducing visible transmittance. The thermal transmittance of the structure is the reciprocal of the total thermal resistance. ISO 9869 describes how to measure the thermal transmittance of a structure experimentally. An object's transparency is measured by its total transmittance. Complementary to "R" is the "transmission coefficient", or "transmittance", "T". The R-value is the reciprocal of the thermal transmittance (U-factor) of a material or assembly. In microscopy, the transmittance value is sometimes used. Previous rigid endoscopes suffered from low light transmittance and poor image quality. Previous rigid endoscopes suffered from very low light transmittance and extremely poor image quality. These types of products are NFRC-ratable for visible transmittance.