波拉一步摄影667型黑白胶片的最新进展是,取消以前的照片涂膜过程,称为无涂膜(Coaterless)胶片。黑白胶片的银盐扩散转移法,是硫代硫酸银络盐扩散到含有显影核的相纸接受层上,经显影剂还原成金属银影像。由于硫代硫酸银不可能全部被还原,而硫代硫酸钠也会有少量残留,故在空气中将生成硫代硫酸。而硫代硫酸极易分解成硫酸、亚硫酸、硫、硫化氢等。此种硫化物侵蚀银影而生成淡黄 The latest advancement in Bora’s one-step photography of type 667 black and white film is the elimination of the previous photo coating process, known as Coaterless film. Black-and-white film of the silver salt diffusion transfer method is silver thiosulfate salt diffusion onto the photographic developer layer containing the receiving layer, the developer reduced to a metallic silver image. As thiosulfate can not be all reduced, and sodium thiosulfate will have a small amount of residual, it will generate thiosulfuric acid in the air. The thiosulfate can easily be decomposed into sulfuric acid, sulfurous acid, sulfur, hydrogen sulfide and so on. This sulfide erodes the silver shadow and produces a yellowish color