Photocopying – Projection printing and copying cameras – Multicolor picture
Patent
1986-02-24
1987-07-07
Hayes, Monroe H.
Photocopying
Projection printing and copying cameras
Multicolor picture
355 35, G03B 2780
Patent
active
046783199
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
In general, this invention relates to the field of color exposure of photographic film bases when producing copies of a film original. In particular, this invention relates to a measuring device for selecting the color composition of the copying light in the case of color exposures in photographic enlarging or copying apparatuses.
When making colored enlargements or colored copies of a film frame original, it is normally necessary for obtaining a correct color reproduction to adapt the copying light with respect to color to the original to be copied. A change in the color composition of the original essentially white light of the enlarging or copying apparatus is caused, for example, by the introduction of subtractive color filters into the path of the rays resulting, depending on the depth of introduction, in a larger or smaller effect on the copying light. In order to determine the type and extent of the required filtering, light measuring apparatuses are used frequently by means of which each film frame original to be copied is measured before the copying in regard to its density and color distribution.
STATE OF THE ART
An apparatus for the selection of filters is known, for example, from U.S. Pat. No. 3,819,275. This apparatus has three photocells sensitized in the colors red, green and blue that generate light-intensity-dependent measuring signals for each of the color components red, green and blue of the copying light. From the measuring signals, the ratio of the parts of two primary colors to the part of the third primary color is determined in a computer unit. Finally, the determined ratios are compared with preset reference values and possible deviations are indicated by an indicating device.
When a light measuring apparatus of this type for determining the required filtering is used in practice, a calibration of the apparatus is first carried out relative to a selected reference original for which in a preceding test series the exposure time and filtering for an optimal reproduction were determined. For this purpose, the enlarging apparatus is brought into the basic setting that was previously determined for the reference original and the light coming out of the reference original in the case of this adjustment is measured in the three basic colors. The measured values as reference values for the film frame originals to be copied continuously are stored in the measuring apparatus. Each of the originals to be copied continuously, before the actual exposure, is measured in the same way and the respective adjusted filtering is followed so long that the indicated measured values correspond to the stored values relating to the reference original.
The described method of operation has the objective of creating the color balance existing in the reference original, by means of the corresponding color filtering of the copying light, also in the case of all other originals to be copied. This process is based on the principle of the so-called "integration on gray" according to which the colors contained in one photograph integrate over the whole picture surface into a neutral gray because the taken picture scene typically contains the same proportions of the three basic colors. Based on this principle, a constant color balance is maintained in the color copies if care is taken that the copying light coming from the individual film frame originals has a constant ratio of the basic color parts.
However, the prescribed method of operation leads to unsatisfactory results when an original has dominant colors. In such a case, because of the complete balancing of the deviation from the neutral gray by means of the filtering a cast in the picture copy is obtained that with respect to color is complementary to the dominant color and thus a color reproduction is obtained in the end effect that is falsified with respect to the original. Practical experience has shown that the number of satisfactory copies of correctly exposed film frame originals that, however, have dominant colors is much higher
REFERENCES:
patent: 3090289 (1963-05-01), Gundelfiner
patent: 3647296 (1972-03-01), Long
patent: 3672768 (1972-06-01), Schaub et al.
patent: 3819275 (1974-06-01), Aimi et al.
patent: 4492457 (1985-01-01), Kawada et al.
Durst Phototechnik GmbH
Hayes Monroe H.
LandOfFree
Measuring device for selecting the filter in photographic enlarg does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measuring device for selecting the filter in photographic enlarg, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measuring device for selecting the filter in photographic enlarg will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1659561