Photographic color enlarging system

Claim 2

In a system for making enlarged color prints from color negatives that includes the combination of an enlarger having a source of white printing light and a projection lens; an enclosed passageway between said source and said lens for passage of the light from said source to said lens for projection from the latter; negative holder in said passageway spaced between said source and said lens for supporting a color negative in a position for transmitting therethrough light from said source to said lens; and color correction filters between said source and said negative for correcting color imbalance in the cyan, magenta and yellow colors in said negative: a. generating means for generating first voltage color signals respectively proportional to the saturation of the colors complementary to the red, green and blue colors in a color negative when the latter is in said position in the enlarger; b. a source of a second voltage of opposite polarity to said first voltage color signals; c. means for establishing from said second voltage separate reference voltages respectively of absolute magnitudes equal to the voltage color signal required for the correct printing light for each of the aforesaid colors in said negative; d. means for combining each of said reference voltages with the first voltage for the corresponding color to form an error voltage signal for each color of a magnitude equal to the difference between the reference voltage and the first voltage for each color, having the polarity of the greater voltage; e. electrically actuatable control means for controlling the intensities of the light rays transmitted from said source to a color negative in said holder; and f. means operatively connecting said error signals with said control means for altering the intensities of the rays of printing light transmitted to the color negative for passage through the latter when the latter is in said holder, proportional to the magnitudes of said error voltage signals, whereby the printing light projected through said negative and lens will make a print in which the color is correctly balanced.

Claim 3

In the combination as defined in claim 1: g. means for diverting a small sample of the light from the space in said passageway between said negative holder and said lens and for conducting the sample to said generating means for generating said first voltage color signals from said sample.

Claim 4

In the combination as defined in claim 1: g. said error signal voltages each being in a separate electrical circuit; h. said control means including rotatably supported cyan, magenta and yellow color filters of graduated saturations in said passageway between said source and said negative holder; and i. a servo-motor connected with each filter for separately rotating each filter at a uniform rate and for stopping said rotation when the said error voltage signal and said reference voltage for each color are equal.

Claim 5

In the combination as defined in claim 1: h. the source of said printing light comprising three separate electric lamps and electrical circuit connecting the error signal voltages with each lamp; i. a cyan, magenta and yellow color filter stationarily positioned across the light rays from each source; j. a controller in each of said electrical circuits for automatically increasing or decreasing the light output of each lamp in inverse proportion to the magnitude of the error signal whereby the light output will decrease in quantity with an increase in said error signal voltage and will increase in quantity with a decrease in said error voltage until said error signal voltage for each color is substantially equal to said reference voltage.

Claim 6

In a system for making enlarged color prints from color negatives that includes the combination of an enlarger having a source of white printing light and a projection lens, an enclosed passageway between said source and said lens for passage of light from said source to said lens for projection from the latter, a negative holder in said passageway spaced between said source and said lens for supporting a color negative in a position for transmitting therethrough light from said source to said lens, and color correction filters of cyan, magenta and yellow between said source and said negative for correcting color imbalance in the red, green and blue colors in said negative: a. a light carrier for conducting a sample of the printing light from the space in said passageway between said color negative, when in said position, and said lens to a discharge point for discharge from said carrier, while permitting the remainder of light rays in said passageway to be projected onto printing paper; b. a red, green and blue filter supported for movement, in succession, past said discharge point in intercepting relation relative to the rays of light discharged from said point for transmission of said rays therethrough and means connected with said filters for so moviing them; c. a photomultiplier having a D.C. power supply supported in a position for intercepting the rays of light transmitted through said red, green and blue filters, whereby pulsating D.C. voltages representative of the red, green and blue light rays from said source will be generated; d. means for amplifying the voltages so generated, and means for segregating the amplified voltages into separate groups respectively representative of the sums of said red, green and blue rays; e. conductors for conducting the voltages of said groups to separate summing stations, one for each group, and each conductor including a manually actuatable potentiometer and an electronic integrating network for effecting a smooth D.C. voltage at each summing junction of an amplitude proportional to the magnitude of its generative color; f. a source of fixed voltage of opposite polarity to the voltages of said groups at said summing junctions, and an attenuator for conducting the fixed voltage from said last mentioned source to each of said summing junctions including manually actuatable means for adjusting the voltage from each attenuator to deliver at each summing junction a voltage of an absolute magnitude for providing the correct intensity of printing light for each color in the negative in said holder whereby an error voltage signal will be produced at each summing junction equal to the difference between the two voltages and of the polarity of the larger of the two; g. electrically actuatable control means respectively automatically actuated by said error voltage signals for modifying the intensity of the enlarging light to produce the correct intensity in said enlarging light for each color.

Claim 7

In a system for making enlarged color prints from color negatives that includes the combination of an enlarger having a source of white printing light and a projection lens, an enclosed passageway between said source and said lens for passage of light from said source to said lens for projection from the latter, a negative holder in said passageway spaced between said source and said lens for supporting a color negative in a position for transmitting therethrough light from said source to said lens, and color correction filters of cyan, magenta and yellow between said source and said negative for correcting color imbalance in the red, green and blue colors in said negative: a. a light carrier for conducting a sample of the printing light from the space in said passageway between said color negative, when in said position, and said lens to a discharge point for discharge from said carrier, while permitting the remainder of light rays in said passageway to be projected onto printing paper; b. a red, green and blue filter supported for movement, in succession, past said discharge point in intercepting relation relative to the rays of light discharged from said point for transmission of said rays therethrough and means connected with said filters for so moviing them; c. a photomultiplier having a D.C. power supply supported in a position for intercepting the rays of light transmitted through said red, green and blue filters, whereby pulsating D.C. voltages representative of the red, green and blue light rays from said source will be generated; d. means for amplifying the voltages so generated, and means for segregating the amplified voltages into separate groups respectively representative of the sums of said red, green and blue rays; e. conductors for conducting the voltages of said groups to separate summing stations, one for each group, and each conductor including a manually actuatable potentiometer and an electronic integrating network for effecting a smooth D.C. voltage at each summing junction of an amplitude proportional to the magnitude of its generative color; f. a source of fixed voltage of opposite polarity to the voltages of said groups at said summing junctions, and an attenuator for conducting the fixed voltage from said last mentioned source to each of said summing junctions including manually actuatable means for adjusting the voltage from each attenuator to deliver at each summing junction a voltage of an absolute magnitude for providing the correct intensity of printing light for each color in the negative in said holder whereby an error voltage signal will be produced at each summing junction equal to the difference between the two voltages and of the polarity of the larger of the two; g. electrically actuatable control means respectively automatically actuated by said error voltage signals for modifying the intensity of the enlarging light to produce the correct intensity in said enlarging light for each color.

Claim 8

In the combination as defined in claim 5: h. said cyan, magenta and yellow filters beinG of graduated saturation and supported for rotation across the rays of light from said source to said negative holder; i. said control means including a servo-motor connected with each of said cyan, magenta and yellow filters for rotating them in one direction through progressive changes of saturation.

Claim 9

In the combination as defined in claim 5: h. said means for rotating said red, green and blue filters and being connected with the means for segregating said voltages into said groups for synchronous actuation.

Claim 10

In the combination as defined in claim 5: h. said cyan, magenta and yellow filters being stationary and said source of printing light comprising three separate lamps and an electrical circuit connecting the error signal with each lamp; and i. said control means comprising a controller in each of said circuits for automatically increasing or decreasing the light output of each lamp in inverse proportion to the magnitude of the error signal connected therewith whereby the light output for each lamp will decrease in quantity with an increase in said error signal voltage and will increase in quantity with a decrease in said error voltage until said error signal voltage for each color is substantially equal to said reference voltage.