Photography is based on principles of light, optics, and chemistry. For the purpose of producing a photograph, these silver salts are distributed in gelatin to make a mixture called an emulsion, which is applied to film or another supporting material in a thin layer. When the emulsion is exposed to light, the silver halide crystals undergo chemical changes and, after further processing, an image becomes visible. The stronger the light that strikes the crystals, the denser or more opaque that part of the film becomes. Most types of film produce a negative image, from which a positive final copy can be printed on sensitized paper. The dense (or dark) areas of the negative translate into light areas on the final photograph. Almost all modern photography relies on this negative-to-positive process.
- photography [fəˈtɔɡrəfi] n.摄影
- principle [ˈprinsəpl] n.原则
- optics [ˈɔptiks] n.光学
- silver salt [ˈsilvə - sɔ:lt] n.银盐
- distribute [disˈtribju:t] v. 分布，散布(over)
- gelatin [ˈdʒelətin,ˈdʒeləˈti:n] n.凝胶
- emulsion [iˈmʌlʃən] n. 感光乳剂
- apply [əˈplai] v. 涂， 搽， 撒
- film [film] n. 胶片
- layer [ˈleiə] n. 垫片，层
- expose [iksˈpəuz] v. 曝光，暴露
- halide [ˈhælaid] adj.卤化物(的)
- crystal [ˈkristəl] n. 晶体
- undergo [ˌʌndəˈɡəu] v. 经历(变迁等)；遭受(苦难等)
- processing [prəuˈsesiŋ] n.处理
- image [ˈimidʒ] n. 影像
- strike [straik] v. 照在……上
- opaque [əuˈpeik] adj. 不反射光线的
- negative image [ˈneɡətiv - ˈimidʒ] n. 底片(负像)
- sensitized paper [ˈsensitaizd - ˈpeipə] n. 感光纸
- translate into [trænsˈleit - ˈintu] v. 转化为
- rely on [riˈlai - ɔn] v. 依赖，依靠
