Sensitising Dyes in Scientific Photography

Abstract

IN his Friday evening discourse at the Royal Institution on January 31, Dr. C. E. K. Mees discussed “Sensitising Dyes and their Use in Scientific Photography”. While the eye is sensitive to the visible spectrum, and the brightest colours to the eye are yellow, green and red, photographic materials are in their nature sensitive only to the blue-violet and ultra-violet regions of the spectrum, to which the eye has little or no sensitiveness. In 1873, H. Vogel discovered that the addition of dyes to photographic materials would make them sensitive for the region of the spectrum which was absorbed by the dye, and although Vogel's discovery was at first received with incredulity, it eventually proved the foundation of the change in photography which has been effected by the introduction of ortho-chromatic and panchromatic materials. Until the beginning of the twentieth century, only ortho-chromatic plates were available, but in 1904 a series of dyes were made in Germany which sensitised plates very readily for those regions of the spectrum which are bright to the eye, notably the red and yellow, and the first commercial panchromatic plates were made in England in 1906.