film speed的意思|示意

Film speed　refers to the sensitivity of a photographic film to light, which determines for how long the film will be exposed in order to yield a satisfactory image. As the sensitivity of a film increases, the film speed increases, hence making the necessary exposure time shorter.

一般讲，film speed 指的是一张胶片对光敏感度，这决定了为了获得满意的照片，需要暴露多长时间。当胶片的敏感度增加时，film speed也会增加，这样一来，必要的曝光时间就会变短。

Film speed is usually measured in and expressed as an ASA (American Standards Association) or DIN (Deutsches Institut fur Normung) rating. Typical film speeds range from ISO 25 to ISO 1600. The lower the number, the lower the film speed, meaning the film is less sensitive to light and requires longer exposure time. Higher numbers, on the other hand, represent faster film speeds and shorter exposure times.

一般情况下，film speed 通常用ASA（美国标准协会）或DIN（德国标准化学会）指数来衡量和表达。典型的film speeds 从ISO 25 到ISO 1600不等。数值越低，film speed就越低，这意味着胶片对光更不敏感，需要曝光时间更长。另一方面，数值越高，film speed就越高，曝光时间就越短。

When choosing a film speed, a photographer needs to consider the available light in the environment as well as the desired look of the final image. Generally, higher film speeds are suitable for daylight photography or brightly lit scenes, while lower film speeds are suitable for low light photography or for creating a longer exposure blur.

在选择film speed的时候，摄影师需要考虑当前所处的环境里的可用光照以及最终照片需要达到的效果。一般来说，film speed越高则更适合日光拍摄或照明充足的场景，而film speed越低，则更适合低光照拍摄或创造更长时间的曝光模糊效果。

When film speed is used correctly, it can help create beautiful and interesting images. Photographers should experiment with different film speeds depending on their intended results.

当film speed正确使用时，可以创造出漂亮、有趣的照片。摄影师应该根据他们想要达到的效果，尝试不同的film speeds。