Using certain simplification and approximation

this paper analyses the measures for improving the uniformity of illuminance of integrating sphere used for the measurement of veiling glare Index(VGI) and light distribution over the field of photographic objectives from the basic theories about the integrating sphere. Experiments and discussions are presented in combination with the development of ZG-2 VGI measurement instrument. It has been shown that the key may of improving the uniformity is to make use of a Lambertian-like source as the illuminance source. By careful consideration and approaches the deviation in the uniformity over half of an integrating sphere of diameter of 1.6 meter can be less than ?3 percent which is much better than the requirement of draft proposal for ISO standard.