| 摘要 |
<p>PURPOSE:To enable accurate photometry to be performed with simple circuits by performing memory type photometry in such a manner that the integrated current for exposure determination becomes equal to an initial value until shutter curtains become fully open and controlling exposure by the use of the photocurrent amplification factor information outputted in the final after the full opening. CONSTITUTION:A mirror up signal causes a mirror to start ascending. When it ends ascending, the photocurrent amplification information Va having been stored in a microcomputer 11 is inputted from the DA converter 12 of an amplification control circuit 4 to a constant current circuit 2 which in turn supplies the current IREF to a photocurrent amplifying circuit 1, thereby controlling the amplification factor. The substituting characteristic value VB2 determined by the IREF and the photocurrent Ii from a silicon photodiode SPD is sampled (n) times by way of an AD converter 13, and its mean value VB2S is determined. When the front curtain starts traveling, a transistor Q5 is turned OFF by a switching driver 7, by which integration is started and Va is outputted so that VB2 becomes equal to VB2S. After the full opening, controlling is performed by using the final Va. Thereby, the accurate photometry may be performed with the simple circuits.</p> |
