Arrangement for determining the filter setting in colour enlargers

摘要

In the colour analysers which are most commonly used the spectral composition of the light which is emitted by the enlarger lens and is intended for exposing the photographic paper is adjusted in such a manner that the mean value which is taken of the colours over the entire picture is "grey". In the case of colour preponderances in the picture this leads to faulty filtrations. Known arrangements which make it possible to assess and filter the picture with the aid of a video monitor are complex and expensive in terms of apparatus. The novel arrangement shall make it possible to set the filters by means of assessing the picture on the video monitor, while having at the same time a simple construction. The beam bundle leaving the enlarger lens is concentrated by means of a simple convex lens arrangement in such a manner that an image of the negative in the enlarger is produced on the target of a colour video camera by means of its own lens system. In the convex lens arrangement which has to be calculated in a known manner for the focal length of the respective enlarger lens the first lens has to be treated as an auxiliary (supplementary) lens and the second as a field lens.