Photocopying – Projection printing and copying cameras – Multicolor picture
Patent
1986-05-22
1988-03-01
Hix, L. T.
Photocopying
Projection printing and copying cameras
Multicolor picture
355 77, G03B 2772
Patent
active
047289929
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
In general, this invention relates to the field of color exposure of photographic emulsion carriers when producing copies or enlargements of a film original and concerns a process and a device for adjusting an enlarging or copying apparatus, in which case adjusting means the adjustment to a basic adjustment that, with respect to a given film paper combination, results in optimal exposure conditions for a selected film frame original having a medium distribution of color and lightness.
STATE OF THE ART ON WHICH THE APPLICATION IS BASED
The adjustment of a color enlarging apparatus with respect to a given film paper combination is not without difficulty and requires a considerable expenditure of time and material since as a rule several attempts must be made and a number of test copies must be produced.
The procedure in this case is usually such that at first in a test exposure, a first copy is made of a selected test orginal and this copy is visually evaluated. From the density errors and/or color errors that such a test copy usually has, the required corrections are determined empirically and the adjustment of the enlarging apparatus is reset correspondingly. The procedure is repeated until a test copy has the desired quality and the adjustment that resulted in this picture is used as the basic adjustment of the enlarging apparatus for the other film frame originals to be copied.
The evaluation of the test copies and especially the correct assessment of possible color abnormalities in view of the determination of the type and extent of the required corrections requires a high degree of experience, and usually different steps are required until the desired result is achieved which in addition depends on the subjective judgment of an operator.
Predominantly from the graphic field, the use of so-called densitometers is known for color density measurements on picture reproductions. Densitometers are especially known for measuring color deviations with respect to a target copy in which given reference values can be stored and the measured values are indicated as a deviation from the stored reference values. However, densitometers of this type are relatively complicated to handle and in addition, because of their high costs, are unsuitable for a wider use by amateurs. In addition, there is the difficulty of an exact conversion of the measured values indicated by the densitometer into a corresponding correction of the exposure time and/or of the color composition of the copying light. The reason is that the adjusting control means for adjusting the color filtering at the enlarging apparatus are usually not graduated in densitometric units and, in addition, during the conversion, the gamma value of the used copying material must be taken into account so that the work with measuring apparatuses of this type also requires specific experience.
DISCLOSURE OF THE INVENTION
It is the objective of the invention to provide a process and a device for adjusting a color enlarging or copying apparatus by means of which the adjustment may be carried out on the basis of objective measurements in a small number of steps without any specific experience, in which case the device must be simple to handle and cost-effective with respect to manufacturing.
Because the copying light of the enlarging apparatus is used to directly illuminate the reference copy and test copy, a change of intensity or of the color composition of the copying light can be perceived directly on the indicating device which provides the possibility of the direct conversion of an indicated deviation between the test copy and the reference copy into a correction of the exposure conditions by correspondingly influencing the copying light. The absence of a separate measuring light source makes the measuring device especially cost-effective and its costs are clearly below those of the known densitometers which mostly use expensive light sources of high constancy.
The use of a reference copy and the carrying-out of the measurement as a comparat
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Vikoler Florian
Vinatzer Alex
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Hix L. T,.
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