Effect of Elimination of the Specular Component on Efficiency and Error of the Integrating Sphere
John A. Jacquez, Hans F. Kuppenheim · Journal of the Optical Society of America · 1956
Given a perfect comparison type integrating sphere and a standard with perfectly diffuse reflection, the black cups (as used on the General Electric recording spectrophotometer) for eliminating the specular reflection component cause a decrease of efficiency, do not effect the sphere error, but may increase the actual error because the total flux measured is decreased while the instrumental error remains constant.