The present invention relates to apparatus for making test exposures on webs of photosensitive material, particularly for applying test exposures to unexposed fields of photographic films having perforated marginal portions and exposed film frames.
German Offenlegungsschrift No. 1,447,528 discloses the possibility of making test exposures between the perforations in marginal portions or zones of color photographic negatives. Such test exposures are to be used to facilitate the selection of appropriate filters and are to be applied prior to transport of photographic film with exposed film frames through a developing machine. The selection of filter is to be made prior to the making of color prints and should involve the comparison of developed test exposures with a color chart. The aforementioned German printed publication does not disclose any means for applying test exposures to the marginal portions or zones of color film negatives.
The making of test exposures of marginal portions or zones of photographic films with exposed film frames must be carried out with a high degree of accuracy because certain portions of such marginal zones are removed as a result of the making of perforations for film transport and certain other portions of such marginal zones are provided with lettering or other symbols which are normally exposed on photographic film. Thus, the space which is available for the application of test exposures is limited which, in turn, necessitates the making of such exposures with an extremely high degree of accuracy. A very high degree of accuracy is desirable on the additional ground that the test exposures must be detected in a fully automatic way for the purpose of comparison with the aforediscussed color chart. Thus, when a film, one marginal zone or portion of which has test exposures applied thereto, enters the copying apparatus, the locus of test exposures must be ascertained by automatic detector means in order to insure that the copying operation will be carried out at a high speed and will result in the making of acceptable prints. Still further, the color temperature of fields which are provided with test exposures must be constant in order to insure that such test exposures will be capable of adequately serving their purpose in connection with determination of the quantities of printing light in various colors.