你知道不可见光是什么？
Photographic film is a sheet of plastic (polyester, PET, nitrocellulose or cellulose acetate) coated with an emulsion containing light-sensitive silver halide salts (bonded by gelatin) with variable crystal sizes that determine the sensitivity, contrast and resolution of the film. When the emulsion is sufficiently exposed to light (or other forms of electromagnetic radiation such as X-rays), it forms a latent (invisible) image. Chemical processes can then be applied to the film to create a visible image, in a process called film developing.
link:
http://en.wikipedia.org/wiki/Photographic_film
真是丢任先眼没个够啊！
谢谢你送乐呵！
