| 释义 |
halation|həˈleɪʃən|
[irreg. f. halo + -ation.]
a. Photogr. The term used to denote the spreading of light beyond its proper boundary in the negative image upon the plate, producing local fog around the high lights, or those portions of the picture which are brighter than the rest of the image (Cycl. Photogr.).
1859G. W. Perry in Jrnl. Photogr. Soc. Lond. 15 Nov., [The phenomenon] to which, until a better one is found, I have applied the term halation. 1881Athenæum No. 2826. 857 Papers read: ‘Halation’, by Capt. Abney. This was shown not to arise from any turbidity in the glass, but from light being reflected from the back of the plate.
b. A similar effect in television (see quots.).
1937A. T. Witts Television Cycl. 56 Halation, the reflection of image rays by the back of a screen or film. Such reflection produces a blurring of the image as viewed by the observer, or is reproduced on the film. 1940[see blooming vbl. n.1 3]. 1958Chambers's Techn. Dict. Suppl. 983/2 Halation, bright annular area around the cathode-ray tube phosphor spot, arising from internal reflection within the glass support. |