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照相过程可视为具有兆级增益的“固体放大器”。假如我们设法仔细地“调整”它,可能获得更高增益。但是,许多科学照相工作必须在非常低(或非常高)的照度下进行,由于出现所谓“互易律失效”,结果使这种更高增益难于实现。低照度互易律失效(LIRF) 天文研究对象多为暗弱天体。为了记录它们的信息,照相底片的露光时间常达数分钟乃至数小时。此种情况下,欲在照相底片上获得一定光密度的星象,所需要的光能量要比正常曝光时多的多。换言之,在低照度下,照相底片的灵敏度大大降低(可下降10倍以上),出
Photographic process can be regarded as a “solid state amplifier” with a trillion-level gain. If we try to “fine tune” it carefully, we may gain even more. However, many scientific photographic work must be carried out at very low (or very high) illumination levels, with the result that such higher gains are difficult to achieve as a result of the so-called “reciprocity law failure.” Low illumination reciprocity law failure (LIRF) astronomy research object mostly faint objects. In order to record their information, photographic film exposure time of up to minutes or even hours. In this case, to get a certain optical density on the photographic film of the stars, the required light energy than normal exposure more. In other words, under low illumination, the sensitivity of the photographic film is greatly reduced (can be reduced more than 10 times), out