| 摘要 |
PURPOSE:To attain center preferential average photometry with respect to the photometric characteristic by changing stepwise the reflection factor of a half- transmission part, which branches the optical path in a prism, to adjust the photometric characteristic. CONSTITUTION:The luminous flux focused by a photographic lens 1 is reflected on a mirror 2 to form an image on a focusing screen 4, and this light is reflected on prisms 5 and 6 and is emitted from a surface S6 and reaches an eye 8 through an eyepiece lens 7. A half-transmission part 9 is provided on a surface S3 of the prism 5 to lead a part of the luminous flux to a photodetector 10. Since the reflection factor of the half-transmission part 9 is reduced stepwise toward a surface S1', the dense distribution of light under the center of the picture on the photometric sensitivity distribution is reduced to attain center preferential average photometry. |
