 This was then placed in register with a viewing screen of the same type as used for exposure, to produce a limited-colour transparency that could be viewed by transmitted light.The Joly process was introduced commercially in 1895 and remained on the market for a few years.However, it was expensive and the commercially available emulsions of the time were not sensitive to the full range of the spectrum, so the final colour image could not achieve the look of "natural colour".