引言一幅照片在印放之前要选择适宜的照相纸,考虑画面的最大影调范围,即照相纸所能表达景物的最大亮度和最小亮度之比。前者指纯白的、没有银沉积的最小密度部位;后者指最黑的、卤化银全部还原为金属银的最大密度部位。然而,照相纸的最大密度远比透明片的最大密度低,这是因为投射到照 Introduction A photo before printing should choose the appropriate photo paper, taking into account the maximum range of the film, that is, photographic paper can express the maximum brightness of the scene and the ratio of the minimum brightness. The former refers to the white, no silver deposition of the minimum density of the site; the latter refers to the darkest, silver halide all reduced to the largest part of the metal silver density. However, the maximum density of photographic paper is far less than the maximum density of the transparency, because