US3282190A - Photographic colour printing - Google Patents

Photographic colour printing Download PDF

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Publication number
US3282190A
US3282190A US317190A US31719063A US3282190A US 3282190 A US3282190 A US 3282190A US 317190 A US317190 A US 317190A US 31719063 A US31719063 A US 31719063A US 3282190 A US3282190 A US 3282190A
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United States
Prior art keywords
photocell
light
filter
green
colour
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US317190A
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English (en)
Inventor
Neale Denis Manktelow
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Ilford Imaging UK Ltd
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Ilford Ltd
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Publication date
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B27/00—Photographic printing apparatus
    • G03B27/72—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus
    • G03B27/73—Controlling exposure by variation of spectral composition, e.g. multicolor printers
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B27/00—Photographic printing apparatus
    • G03B27/72—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus
    • G03B27/73—Controlling exposure by variation of spectral composition, e.g. multicolor printers
    • G03B27/735—Controlling exposure by variation of spectral composition, e.g. multicolor printers in dependence upon automatic analysis of the original

Definitions

  • This invention relates to photographic printing and in particular to the printing of multicolour photographic transparencies by optical projection on to photosensitive print material.
  • magenta filter produces a reduction not only in the intensity of green light but also in the intensity of blue light due to the unwanted blue absorption of any practical magenta.
  • a cyan filter may afi'ect green and blue light as well as red.
  • red, green and blue light intensities are greatly simplified if the ratio of intensities of two colours may be assessed by a Single operation. As a filter is adjusted to modify the intensity of light of one colour, its eiiect on a second colour is thereby taken into account. If the ratio of red and green light intensities is adjusted by adding or removing a cyan filter, for example the green absorption of the cyan filter is taken into account. The intensity of blue light may be affected by adjustment of the cyan filter, but a subsequent adjustment of blue light intensity by a yellow filter will not greatly disturb the red/ green intensity ratio already established.
  • the sensitivities of practical photocells vary s-ufficiently from day to day to give rise to significant errors in the establishment of a required intensity ratio between two colours. It is therefore preferred to use a single photocell for the assessment of an intensity ratio of two colours. A change in photocell sensitivity will not then affect the assessment of intensity ratio provided the special sensitivity of the photocell remains unchanged, i.e. the sensitivity to any one wavelength remains in a fixed proportion to the sensitivity at any one other wavelength.
  • the photocell is used in a circuit arrangement providing a logarithmic relation between electrical output and incident light intensity, the sensitivity becomes substantially independent on enlarger magnification.
  • light of two colours A and B may be allowed to fall alternately on the photocell, producing output voltages E and E respectively.
  • the difference between the output voltages is thus an indication of the ratio of photocell currents corresponding to the two colours.
  • a method of making from multicolour transparencies prints on photographic material containing at least two components selectively sensitive to two different spectral bands comprises allowing printing light to fall on a photocell, cyclically interposing in the path of said light a filter passing one of said spectral bands but not the other, passing current from said photocell through a logarithmic amplifier, adjusting the relative intensities of light in the two spectral bands to an adjusted proportion which produces in the output of the logarithmic amplifier an alternating component of current of predetermined amplitude and exposing said photographic material by printing light having relative intensities of light in the two spectral bands in said adjusted proportion.
  • the photocell is of the electron multiplier type and is operated at substantially constant collector current, part of the dynode supply voltage to said electron multiplier being applied to a logarithmicamplifier from the output of which an alternating voltage is obtained which is used as a measure of the ratio of intensities of light of the colours. in the two spectral bands.
  • FIG. 1 represents a side elevation of the photocell unit and associated colour selective filters.
  • FIG. 2 represents a plan view of the same unit.
  • FIG. 3 represents the electrical circuit of the photocell power supply and logarithmic amplifier.
  • FIG. 4 represents the A.C. amplifier and meter circuits.
  • FIGS. 3 and 4 constitute a single circuit when that of FIG. 3 is placed to the left of that of FIG. 4.
  • the filter 2- is an Ilford No. 109 Yellow which therefore passes the green and red components of printing light but absorbs the blue.
  • the sector disc 3 rotates at 3,000 r.p.m. and comprises two transparent sectors 5 and 6 of 90 each and two sectors 7 and 8 also of 90 each which are covered with Ilford filter No. 204 Red.
  • red light may at all times pass freely through yellow filter 2 and the disc to reach the multiplier photocell 1'.
  • Green light passing the yellow filter 2 is modulated by rotation of the disc 3, since sectors 5 and 6 transmit green light freely, but sectors 7 and 8 absorb it. It follows, therefore, that the photocell is alternately receiving red light alone and red light and green light simultaneously. This is the condition of the apparatus providing an indication of the ratio of green light to red light.
  • magenta filter 9 (Ilford N0. 502) is I slid into the operative position formerly occupied by the yellow filter 2.
  • magenta filter 9 prevents green light from reaching the photocell. Blue light passing the magenta filter 9 is then modulated by rotation of the disc 3, whereas red light reaches the photocell substantially without modulation.
  • the current emitted by the cathode of photocell 1 comprises a DC. component corresponding to the unmodulated red light intensity and an A.C. component at 100 c./s. corresponding to the modulated green or blue light reaching the cathode.
  • the photocell is'connected in the circuit shown in FIG. 3. This is based closely on the arrangement described by Hariharan and Bhalla and its function has been described by them (100. cit.).
  • the circuit of FIG. 3 continuously controls the amplification of the multiplier photocell so that the collector current of the photocell is substantially constant at any instant. To do this it varies the photocell supply voltage in sympathy with the incident light intensity.
  • the alternating component of the output of the logarithmic amplifier is applied to the grid of the tuned amplifier V8.
  • the anode load of this amplifier is a circuit tuned to the fundamental frequency at which the green or blue light is being chopped, viz. 100 c./s. From the .tuned amplifier the 100 c./s. signal passes to a negative feed-back amplifier comprising valves V911 and V9b.
  • the A.C. output of this amplifier is rectified by diodes MR3 and MR4 to produce across R31 a DC. voltage proportional to the A.C. output of the negative feed-back amplifier.
  • the cathode follower V10a applies this DC. voltage to one side of the meter M.
  • the second cathode follower V10b applies to the other side of the meter a potential determined by the settings of potentiometers RV7 and RV8 or RV9.
  • the potentiometers RV7, RV8 and RV9 may be marked with linear scales in terms of colour density units.
  • the green control, RVS may be calibrated to indicate positions which will maintain a given deflection on the meter M as dilute green-absorbing (magenta) filters of 1 equal strength are inserted in the path of light reaching the multiplier photocell 1.
  • the marked increments will correspond to the successive addition of filters of green-light density 0.05.
  • the blue control RV9 will be marked in increments of yellow density and the red control in increments of cyan density.
  • the negative to be printed is now replaced by the test negative.
  • the green control RV8 may be adjusted to restore meter M to zero indication.
  • Yellow filter 2 is now removed from operative position and replaced by magenta filter 9 and switch S1 is moved to thealternative position.
  • the blue control RV9 is now adjusted to restore meter M to zero indica- -tion.
  • the new combination of settings of RV7, RV8 and way after RV8 has been adjusted to suit the negative being examined, it is then necessary to return filter 2 to operative position, return switch S1 to the position indicated and readjust RV8.
  • An alternative method of using the apparatus comprises adjusting the controls RV4, RVS, RV7, RV8 and RV9 as described above so that the meter provides zero indication with either the yellow or the magenta in operative position before the multiplier photocell and S1 in the appropriate corresponding position.
  • an alternative negative may be substituted for the test negative.
  • the colour correction filters used in the lamphouse may then be adjusted until the meter M again indicates zero with either filter 2 or filter 9 in operative position and with switch S1 in the corresponding condition as described above.
  • the controls RV1 and RV2 are provided to allow the operating conditions of V7 to be adjusted to provide a logarithmic response over the widest possible range of photocell supply voltage.
  • control RV3 provides adjustment of the degree of negative feedback used in the feedback amplifier V9A and V9B. 'It controls the amplification of the amplifier and therefore the sensitivity of the instrument.
  • RV6 controls the current through the potentiometer chain formed by RV7, RV8 and RV9.
  • RV6 By adjusting RV6, it is thus possible to adjust the sensitivity of controls RV7, RV8, RV9 to conform to the sensitivity of the instrument.
  • a didymium glass filter (2 mm. of Chance ON 16) should be placed in the path of light reaching the photocell. This filter is indicated in FIGURE 1 by the numeral 10.
  • a photomultiplier (multiplier photocell) is a combination of a photo-emissive photocell and an electron multiplier contained in the same envelope.
  • the electron multiplier is essentially a linear current amplifier butin conjunction with known arrangements of other'circuit components it may form part of a logarithmic amplifier operating over a dynamic range of 10 to 1.
  • MR3 ZS 74 (rectifier).
  • MR4 ZS 74 (rectifier).
  • V3 EL 360 V3 EL 360.
  • V4 EF 86 V4 EF 86.
  • V7 ECC 83 V7 ECC 83.
  • V9 -ECC 82 V9 -ECC 82.
  • V10 ECC 82 V10 ECC 82.
  • L1 12 H (choke). 1 M1 50-040 ,u.A. (meter), S1 TWO pole changeover switch. T1 Transformer.
  • a method of making from multicolour transparencies prints on photographic material containing at least two components selectively sensitive to two different spectral bands which comprises allowing printing light to pass to a photocell through a didymium glass filter thereby restricting the response of the photocell to the said spectral bands; cyclically interposing in the path of said light a filter passing one of said spectral bands, but not the other, to said photocell; passing current from said photocell through a logarithmic amplifier, adjusting the relative intensities of light in the two spectral bands to an adjusted proportion which produces in the output of the' logarithmic amplifier an alternating current component of predetermined amplitude; and exposing said photographic material by printing light having relative intensities of light in the two spectral bands in such adjusted proportion.
  • a photographic printing apparatus comprising a printing light having two spectral bands of different colors, filter means which are cyclically interposed in the path of said printing light whereby one of the color bands but not the other can be transmitted, a single photocell of the electron multiplier type which operates at substantially constant collector current, said photocell being disposed so that the light transmitted through said filter means will be detected by said photocell, a logarithmic amplifier coupled to said photocell so that the output of said photocell will be operably coupled to said amplifier, circuit means for feeding a portion of the dynode supply voltage of said photocell to said logarithmic amplifier, adjusting means for establishing the relative proportion of printing light in the two spectral bands which reaches said photocell and measuring means to determine the alternating current component output of said logarithmic References Cited by the Examiner UNITED STATES PATENTS Tuttle 88-24 Varden 88-24 Simmon 8824 Hirsch 88-24 X Simmon et a1.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Projection-Type Copiers In General (AREA)
  • Spectrometry And Color Measurement (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
US317190A 1962-10-25 1963-10-18 Photographic colour printing Expired - Lifetime US3282190A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB40486/62A GB994165A (en) 1962-10-25 1962-10-25 Photographic colour printing

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US3282190A true US3282190A (en) 1966-11-01

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US317190A Expired - Lifetime US3282190A (en) 1962-10-25 1963-10-18 Photographic colour printing

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US (1) US3282190A (de)
CH (1) CH438009A (de)
DE (1) DE1447505A1 (de)
GB (1) GB994165A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3527540A (en) * 1967-05-08 1970-09-08 Itek Corp Color concentration discriminators
US3748035A (en) * 1971-12-28 1973-07-24 Xerox Corp Method for sequential illumination in a polychrome process

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2521954A (en) * 1946-05-10 1950-09-12 Eastman Kodak Co Apparatus for making color prints
US2544196A (en) * 1947-08-04 1951-03-06 Pavelle Color Inc Photoelectric color analyzer
US2565399A (en) * 1949-09-30 1951-08-21 Simmon Brothers Inc Machine for making photographic color prints
US2977407A (en) * 1960-02-10 1961-03-28 Hazeltine Research Inc Electronic previewer for photographic processes
US3069971A (en) * 1960-01-18 1962-12-25 Simmon Brothers Inc Exposure control apparatus for making color prints

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2521954A (en) * 1946-05-10 1950-09-12 Eastman Kodak Co Apparatus for making color prints
US2544196A (en) * 1947-08-04 1951-03-06 Pavelle Color Inc Photoelectric color analyzer
US2565399A (en) * 1949-09-30 1951-08-21 Simmon Brothers Inc Machine for making photographic color prints
US3069971A (en) * 1960-01-18 1962-12-25 Simmon Brothers Inc Exposure control apparatus for making color prints
US2977407A (en) * 1960-02-10 1961-03-28 Hazeltine Research Inc Electronic previewer for photographic processes

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3527540A (en) * 1967-05-08 1970-09-08 Itek Corp Color concentration discriminators
US3748035A (en) * 1971-12-28 1973-07-24 Xerox Corp Method for sequential illumination in a polychrome process

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Publication number Publication date
DE1447505A1 (de) 1968-10-24
CH438009A (de) 1967-06-15
GB994165A (en) 1965-06-02

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