| 摘要 |
A contrast mask for a transparent photographic original may be formed by illuminating a photochromic body (11, 41) through the original with white light. Preferably the photochromic body (11, 41) is optically neutral (grey) and contains a silver halide as a photochromically active substance. Preferably the mask-forming exposure is performed separately from the photographic exposure of a recording medium through the original and the mask, by a different light source (27). The optical contrast range of the mask can be varied in response to the optical contrast range of the original by varying the amount of the mask-forming exposure. This variation is preferably effected by varying the number of flashes of the light source (27). …<??>The photochromic body is preferably incorporated in the holder (1, 33) for the transparent original. …<??>Photographic reproduction apparatus may include an automatic densitometer, the output of which controls the amount of the mask-forming exposure. |
