Important characteristics of famous exposure meters, which have been in use now in Japan, were tested by authors in conformity with the rule of Japanese Industrial Standards B 7120 (1957). Results and conclusions obtained by author's tests are as follows:
1) Physical meaning of the effective value of sensitive angle, for which the exposure meter shows the 85%, 70% and 50% indication when facing and covering the source of uniform brightness, was discussed and described here.
2) The directional character of sensitivity for each exposure meter was measured, and furthermore the effective value of sensitive angle for them were calculated depending upon the above data.
3) Upon the practical testing of the effective value of sensitive angle, the influence by the diffusing character of milk-white glass used for light source and by the dimension of it was measured and discussed here.
4) It was recognized, that the ordinary milk-white glass sold by the municipality will be satisfactorily used somehow or other for the practical testing, and the result of it coincided fairly with that of calculation.
5) Calibration tests were tried for the famous exposure meters, and it was found that the errors of them were within the limit of the specification of the Japanese Industrial Standards.
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