US3500737A - Light control arrangement for photographic cameras - Google Patents

Light control arrangement for photographic cameras Download PDF

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Publication number
US3500737A
US3500737A US663324A US3500737DA US3500737A US 3500737 A US3500737 A US 3500737A US 663324 A US663324 A US 663324A US 3500737D A US3500737D A US 3500737DA US 3500737 A US3500737 A US 3500737A
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US
United States
Prior art keywords
light
resistor
current
photosensitive
battery
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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
Application number
US663324A
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English (en)
Inventor
Helmut Mayr
Richard Pelte
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agfa Gevaert AG
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Agfa Gevaert AG
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Publication date
Application filed by Agfa Gevaert AG filed Critical Agfa Gevaert AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44—Electric circuits
    • 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
    • G03B7/00—Control of exposure by setting shutters, diaphragms or filters, separately or conjointly
    • G03B7/08—Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
    • G03B7/081—Analogue circuits
    • G03B7/085—Analogue circuits for control of aperture

Definitions

  • the battery used therein does not provide a constant voltage across the light meter and photosensitive element associated therewith, when severe light variations prevail.
  • the stabilizing elements or components are interconnected, so that when the intensity of light is relatively low, a predetermined amount of current flows through the stabilizing elements as a .result of a constant resistor connected thereto. When the intensity of light is relatively low, a substantially small amount of current flows through the light meter.
  • the objects of the present invention are achieved through a resistor designed so that its resistance value decreases with increasing current through the light meter.
  • the resistor has a large ohmic value when the intensity of light is relatively low. In this manner, only a relatively small amount of current flows through the battery, under these conditions.
  • the current flow through the stabilizing elements is also not above a predetermined level.
  • the ohmic value of the resistor is relatively small. In this man ner the ratio of stabilization current to consumed current or used current, remains substantially constant at high or low intensities of light.
  • variable resistor is made in the form of a variable resistor.
  • the sliding contact of this resulting variable resistor is coupled to the aperture diaphragm or the indicator of the light meter.
  • the same effect of such a variable resistor may be obtained through a further photosensitive resist-or or element.
  • a light control circuit applicable to photographic cameras and in particular, moving picture cameras.
  • the light meter generally associated with such cameras, is operatively connected to the diaphragm of the camera.
  • a photosensitive element is connected in series with the light meter.
  • a battery is connected across the series combination of the light meter and the photosensitive element, and supplies current to these components.
  • Stabilizing components in the form of Zener diodes or battery cells are further connected in parallel with the series combination of the light meter and the photosensitive element. The purpose of such stabilizing components is to maintain the voltage appearing across the light meter and the photosensitive element constant.
  • a variable resistor component is connected in series with the battery and the parallel combination of the stabilizing components and the series combination of the light meter and photosensitive element.
  • variable resistor is arranged so that its resistance varies inversel as a function of the current through the light meter.
  • the variable resistor may be in the form of one having a sliding contact mechanically coupled to the indicator. of the light meter.
  • the variable resistor may be a photosensitive element exposed to the ambient light conditions. The arrangement assures that the current drain of the battery is maintained at a minimum possible value.
  • FIG. 1 shows a moving picture camera having a housing 1 to which is secured a reception lens 2.
  • the housing is also provided with a viewer outlet 3, a window 4 for admitting. the light to be measured, and the release switch 5.
  • FIG. 2 shows the electrical circuit diagram for the camera.
  • a variable resistor 7 Connected in series with a battery 6, is a variable resistor 7.
  • the sliding contact 8 of the variable resistor 7 is mechanically coupled to the aperture diaphragm or to the indicator of an instrument 9 having a rotatable coil.
  • the rotatable coil instrument 9 is connected in the circuit of battery 6 and is in series with a photosensitive cell 10.
  • Zener diodes 11 are provided in parallel to the photosensitive cell 10 and the instrument 9, for the purpose of assuring a constant voltage across these elements.
  • An operating switch 12 is further connected in series with the battery 6. This switch 12 may for example, be coupled ot the release lever or switch 5,
  • FIG. 3 Another embodiment of the invention appears in FIG. 3.
  • the battery 6, instrument 9, and photosensitive cell or resistor 10 serve the same purpose as in the embodiment of FIG. 2.
  • a photosensitive resistor 13 is provided in this particular embodiment.
  • compensating resistors 14 and 15 are connected in series and in parallel with this photosensitive resistor 13.
  • compensating resistors 16 and 17 are connected in series and in parallel with the photosensitive resistor or cell 10.
  • Zener diodes are also applicable to this embodiment, these are replaced with stabilizing cells 18, for the purpose of providing a stabilized voltage.
  • FIG. 4 is a graphical diagram in which the abscissa corresponds to the intensity of the prevailing light, and the ordinates correspond to the logarithm of the currents I.
  • the curve 19 shows the variation of the logarithm of the current I as a function of the prevailing light intensity L.
  • the current I is that current which flows through the instrument 9.
  • the curve 20 indicates the additional loading effect realized due to the stabilization current I in accordance with the embodiments of FIGS. 2 and 3.
  • the current I is that which fiows through the Zener diodes 11 or the stabilization cells 18.
  • the curve 21 shows the characteristics of the stabilization current I prevailing in conventional apparatus.
  • the arrangement in accordance with the present invention, is also applicable for the purpose of stabilizing other types of circuits in which the current from a battery is to be maintained constant under different loads. This pertains particularly to battery operated light meters which are not a part of a photographic camera.
  • a light control arrangement for a photographic camera comprising, in combination, light meter means operatively connected to the diaphragm of said photographic camera; photosensitive means connected in series with said light meter means; a battery connected to said light meter means and said photosensitive means supplying current thereto; stabilizing means connected in parallel with the series combination of said light meter means and said photosensitive means for maintaining constant the voltage across said light meter means and said photosensitive means; and adjustable resistor means connected to said battery and the junction of said stabilizing means and said series combination of said light meter means and said photosensitive means, said adjustable resistor means being adjustably set by said meter means so that the resistance value of said resistor means decreases with increase in current through said light meter means, whereby the current drawn from said battery is maintained at a minimum.
  • said resistor means is a variable resistor means having a sliding contact connected to said diaphragm, the resistance of said variable resistor means being made adjustable through varying the position of said sliding contact.
  • said resistor means is a variable resistor means having a sliding contact connected to the indicator of said light meter means, the resistance of said variable resistor means being made adjustable through varying the position of said sliding contact.
  • a light control arrangement for a photographic camera comprising, in combination, light meter means operatively connected to the diaphragm of said photographic camera; photosensitive means connected in series with said light meter means; a battery connected to said light meter means and said photosensitive means supplying current thereto; stabilizing means connected in parallel with the series combination of said light meter means and said photosensitive means for maintaining constant the voltage across said light meter means and said photosensitive means; adjustable resistor means connected to said battery and the junction of said stabilizing means and said series combination of said light meter means and said photosensitive means, the resistance value of said resistor means decreasing with increase in current through said light meter means, whereby the current drawn from said battery is maintained at a minimum; a first compensating resistor connected in series with said photosensitive resistor; and a second compensating resistor connected in parallel with said photosensitive resistor, said first compensating resistor and said second compensating resistor maintaining the ratio of current through said light meter means to the current through said stabilizing means at a substantially predetermined constant value.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Exposure Control For Cameras (AREA)
US663324A 1966-08-31 1967-08-25 Light control arrangement for photographic cameras Expired - Lifetime US3500737A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEA0053381 1966-08-31

Publications (1)

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US3500737A true US3500737A (en) 1970-03-17

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Application Number Title Priority Date Filing Date
US663324A Expired - Lifetime US3500737A (en) 1966-08-31 1967-08-25 Light control arrangement for photographic cameras

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US (1) US3500737A (de)
AT (1) AT269634B (de)
DE (1) DE1497912A1 (de)
GB (1) GB1190989A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3670639A (en) * 1968-12-16 1972-06-20 Gen Electric Flexible electronic integrated circuit camera control assembly

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2964655A (en) * 1958-06-04 1960-12-13 Bell Telephone Labor Inc Transistor trigger circuit stabilization
US3000280A (en) * 1955-11-09 1961-09-19 Voigtlaender Ag Photographic camera with automatic adjustment of exposure conditions
US3298773A (en) * 1963-09-20 1967-01-17 Agfa Ag Exposure controls for motion picture cameras
US3313224A (en) * 1963-06-01 1967-04-11 Agfa Ag Automatic aperture control for photographic cameras
US3383566A (en) * 1964-12-02 1968-05-14 Bell & Howell Co Diode control of voltage in an exposure control circuit
US3394642A (en) * 1965-06-01 1968-07-30 Elmo Co Ltd Electrical circuit for automatically controlling an aperture device for a photographic camera

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3000280A (en) * 1955-11-09 1961-09-19 Voigtlaender Ag Photographic camera with automatic adjustment of exposure conditions
US2964655A (en) * 1958-06-04 1960-12-13 Bell Telephone Labor Inc Transistor trigger circuit stabilization
US3313224A (en) * 1963-06-01 1967-04-11 Agfa Ag Automatic aperture control for photographic cameras
US3298773A (en) * 1963-09-20 1967-01-17 Agfa Ag Exposure controls for motion picture cameras
US3383566A (en) * 1964-12-02 1968-05-14 Bell & Howell Co Diode control of voltage in an exposure control circuit
US3394642A (en) * 1965-06-01 1968-07-30 Elmo Co Ltd Electrical circuit for automatically controlling an aperture device for a photographic camera

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3670639A (en) * 1968-12-16 1972-06-20 Gen Electric Flexible electronic integrated circuit camera control assembly

Also Published As

Publication number Publication date
GB1190989A (en) 1970-05-06
AT269634B (de) 1969-03-25
DE1497912A1 (de) 1969-03-27

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