US3828226A - Exposure override control - Google Patents

Exposure override control Download PDF

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Publication number
US3828226A
US3828226A US00316672A US31667272A US3828226A US 3828226 A US3828226 A US 3828226A US 00316672 A US00316672 A US 00316672A US 31667272 A US31667272 A US 31667272A US 3828226 A US3828226 A US 3828226A
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United States
Prior art keywords
exposure
improvement
voltage
time unit
variable
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Expired - Lifetime
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US00316672A
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English (en)
Inventor
G Pamlenyi
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.)
CARLSON CO CHESLEY F
CHESLEY F CARLSON CO US
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CARLSON CO CHESLEY F
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Application filed by CARLSON CO CHESLEY F filed Critical CARLSON CO CHESLEY F
Priority to US00316672A priority Critical patent/US3828226A/en
Priority to DE2361559A priority patent/DE2361559A1/de
Priority to GB5884573A priority patent/GB1416610A/en
Priority to BE139100A priority patent/BE808902A/xx
Priority to JP48141983A priority patent/JPS49110346A/ja
Application granted granted Critical
Publication of US3828226A publication Critical patent/US3828226A/en
Anticipated expiration legal-status Critical
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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

Definitions

  • the apparatus as disclosed is loga- 250/206 214 p rithmically variable so that if control measurements of system density indicate a shift in operating conditions 5 References Cited the error can be directly set on the apparatus.
  • the present invention eliminates the requirement of recalibrating photographic process timing circuits due to chemistry drift, variations in emulsion speeds, or the like. This is accomplished by the creation of means for varying logarithmically the set point of each timing cycle exposure time with one setting on the instrument. This setting relates directly to and compensates for the density shift due to a variation of chemical activity level, emulsion speed of the film or temperature shift of the density. 7
  • this is accomplished in the preferred embodiment by providing a logarithmically variable resistance network which varies the voltage set point indicating the end of a timing cycle.
  • the actual voltage utilized across the resistance network is equivalent to the voltage which initially determines the linearly variable exposure time.
  • Individual resistance values are derived from voltage ratios necessary to produce a logarithmic change in all timing cycles and, thus, any variation of the control increases or decreases the exposure time in density or logarithmical steps in an amount equivalent to the density shift which occurs when the level of chemistry activity deteriorates.
  • FIGURE is a schematic diagram showing my invention connected to the essential elements of an exemplary timing circuit for continuous tone and halftone photographic processes.
  • the improvement which is my invention is also shown in the FIGURE comprising a logarithmically variable network designated generally by the numeral 12. It is utilized, as indicated above, to compensate for variations of chemical activity level, emulsion speed of the film and temperature shifts of the chemistry.
  • the circuit shown in the FIGURE can be utilized in exposing line copy, continuous tone and halftone exposures and in exposing masking films and color separation films.
  • reference will be to halftone exposures. It is to be understood, however, that the control circuit 12 is effective for every process utilized.
  • Three basic exposure techniques are utilized in exposing photographic film to accomplish high quality halftone reproductions. These basic exposure tech niques are conventionally designated main exposure which exposes the film from the illuminated copy with a halftone screen in position over the film, highlight exposure which is an exposure of the film from the illuminated copy with no halftone screen over the film and flash exposure which is an overall exposure of the film with flash lamps with a halftone screen in position over the film.
  • the timing device shown is designed so that for a standard density reading the circuit can be calibrated for the particular operating characteristics to be utilized such as chemical condition, film type, film speed, halftone screen, and the like. This is accomplished with time unit resistors designated l4, l5 and 16 in the FIG- URE, and associated indicia where, for example, one hundred time units would represent ten seconds. Provision is made in the device with the use of switches 17, 18 and 19 to calibrate the apparatus for varying operating conditions on time unit resistor banks maintained externally from the device.
  • These external resistor banks can be referred to as memory banks and would be calibrated for different film speeds or halftone screens or the like and thereafter when operating conditions change all that is necessary is to plug in the retained settings on the external time unit memory bands in external jacks 20, 21, 22, 23, 24, 25.
  • Density variations of a particular piece of work to be copied are set into the apparatus to achieve precise control of the shadow and highlight densities of the finished copy. Electronically the above design is accomplished as follows.
  • Time unit resistances 14, 15 and 16 are provided for each illumination cycle, i.e., main, highlight and flash. As shown in the FIGURE, the time unit resistances are linearly variable resistors on the order of 100 kilohm. These resistors 14, or 16 are selectively connected in parallel with a variable timing capacitor 28 or 29 and therefore, since voltage is directly proportional to resistance, any linear variation in the time unit resistors 14, 15 or 16 linearly varies the voltage impressed across and stored in the capacitor 28 or 29.
  • variable impedances As is known in the art, density variations being related to relative illumination, are logarithmic. Therefore a 0.3 increase in density (antilog equal 1.995) will require double the time duration of illumination. This is accomplished for main and highlight illumination by the variable impedances designated 28 and 32 in the FIGURE wherein the variable resistor 32 is in series with a field effect transistor 34.
  • This arrangement provides a logarithmically variable constant current source which will produce a current through and thus a voltage across the selected time unit resistor 14 or 15 which is variable from between zero and 0.3 density in 0.01 density steps. Since ultimately the time duration of discharge from the variable timing capacitor 28 will determine the timing cycle and since the RC time constant for discharge of a capacitor is directly related to the capacitor size, provision is also made to double capacitor 28 size every 0.3 density.
  • variable resistor 36 As is known in the art, when flash lighting is utilized it produces different characteristic results during processing the main or highlight lamp exposure techniques. Therefore design values for density variation for the flash parameters are obtained from a different formulation and these values are incorporated into the circuit as variable resistor 36 and variable timing capacitor 29.
  • a relay (not shown) is provided controlling interconnected switches 41, 42, 43, 46 and 47 to insert the flash time unit resistor 16, flash density impedances 29 and 36, flash lamp 51 and flash lamp phototube 52 into the timing circuit when the flash exposure is to be performed.
  • calibration and operation of the tim ing circuit is as follows. With a standard density value, such as L00, set on the density dials, time unit values linearly variable in seconds of exposure are set on the time unit resistor banks 14, 15 and 16 shown in the FIGURE. Thereafter these settings will give a consislent reproduction of the highlight and shadow density when using the same film type, film speed, chemistry and halftone screen. Shadow and highlight density variations of a particular piece of work to be copied are set on the apparatus by variation in the density controls comprising the variable density resistors 32 and 36 and variable timing capacitors 28 and 29. As indicated above, the variable resistor 32 and the variable capacitor 28 compensate for density variations in the main and highlight exposures and variable resistor 36 and variable timing capacitor 29 compensate for variations in flash exposure times.
  • a standard density value such as L00
  • time unit values linearly variable in seconds of exposure are set on the time unit resistor banks 14, 15 and 16 shown in the FIGURE. Thereafter these settings will give a consislent reproduction of the highlight and shadow density when using the same film type, film
  • variable timing capacitor 28 is charged to the proper potential from a negative source of voltage through constant current source 31, comprising variable resistor 32 and the field effect transistor 34, conductor 54, relay contact 56 in its normally closed position, conductor 58, contact 43, varaible timing capacitor 28 to ground.
  • the voltage to which the capacitor is charged depends upon the constant current from the constant current source 31 which is controlled by variable resistor 32 as well as the linearly variable resistance value of time unit resistor 14 which is connected across the capacitor 28 through conductor 61, conductor 62, relay contact 41, switch 64, switch 17, variable resistor 14 to ground.
  • the timing cycle is initiated by depressing the start button 66 which energizes a relay 67 from a positive source of voltage through start button 66, resistor 68, relay 67 to ground.
  • relay 67 When relay 67 is energized, it is held by relay contact 69, and normally closed relay contact 56 opens to disconnect the charging circuit while normally open relay contact 70 closes to energize the lamps 72.
  • the lamp 72 When the lamp 72 is energized the phototube 73 conducts and the negative charge of the capacitor 28 is discharged from the capacitor 28 through contact 43, conductor 58, conductor 75, conductor 77, contact 46, phototube 73, to the positive source of voltage as indicated.
  • Monitoring the discharge of the capacitor 28 through phototube 73 is a differential amplifier and comparator 79 connected from point 81 through conductor 75 to the input of the differential amplifier and comparator 79. The discharge is monitored by the differential amplifier and comparator 79 to determine when the capacitor 28 has discharged to a predetermined value.
  • Highlight exposure may be accomplished in the same manner by initially switching manual switch 64 to incorporate the highlight time unit resistor 15. Thereafter initiation of the timing cycle will produce a highlight exposure of a time duration dependent upon the value set on the highlight time unit resistor 15 and the density of the copy as set on the density controls 28, 32.
  • the present invention provides an extremely simple and accurate method of compensating for the density shift without varying the calibration of the timing circuit or recalibrating all prior settings maintained on the memory banks of the time unit values.
  • resistance network 12 an impedance network for control of alternating current timing circuits may be derived or more accurate and sophisticated resistance circuits can be constructed such as a parallel-series arrangement of equal value resistors to produce the same result. Resistance values have been derived based on the antilogarithm of voltage ratios yielding density variations which decrease or increase the time duration of illumination controlled by the time unit resistors 14, 15, 16 or external memory banks plugged into external jacks 20-25, if utilized.
  • the magnitude of the overall resistance for the control should preferably be selected within the accuracy limitation of the time unit resistances 14, and 16. For example, in the embodiment shown resistance values on the order of 100 kilohm resistance are utilized for the time unit resistors l4, 15, 16. Thus an overall resistance value of three or five megohm for the control resistance 12 would draw an error current of 0.33 percent or 0.2 percent, respectively. Either of these are well within the design accuracy of the unit.
  • Design values for the individual control resistances 102-122 to yield a proportional logarithmic variation in illumination times are obtained as follows.
  • the selected variable timing capacitor 28 or 29 When operating under normal conditions, with no compensation from an override circuit, the selected variable timing capacitor 28 or 29 would be charged to the voltage across the selected time unit resistance bank 14, 15 or 16 (hereinafter referred to as E When discharging, this voltage is monitored by the differential amplifier and comparator 79.
  • the override circuit .12 is designed to vary the effective voltage across the input to the differential amplifier and comparator 79 (hereinafter referred to as E by an amount equivalent to the density shift noted on the finished copy.
  • the value of the density shift is dialed into the conttol switch 99. As is shown in the FIGURE indicia of between +0.1 density shift to 0.1 density shift in 0.01 density steps are utilized on the control.
  • the ratio of the voltage across the time unit resistors (E to the effective voltage (E must be varied logarithmically in 0.01 density steps. Ratios are accordingly obtained by deriving antilogarithms of the 0.01 units from 0.0 to 0.2.
  • values of overall R, to ground may be derived for each override control density step from 0.0 to 0.2.
  • Individual values for resistors 102-122 in the control circuit 12 can be obtained by noting the difference between each successive R To gain the ability to vary the control in both the positive and negative direction the 0.1 value is designated as 0.0 on the control indicia.
  • the timing circuit is then calibrated so that at that setting the proper time duration of illumination as indicated by the time unit resistors and their associated indicia will take place. Thereafter any variation in the override control will increase or decrease illumination and thus copy density in the following manner.
  • This voltage is also impressed across the override control resistors 102-122 from point 96 through control resistors 102-122 to ground.
  • the logarithmic proportion of this voltage E corresponding to 0.01 density variations, taken from switch contact 101 is connected by conductor 124 to the input of the differential amplifier and comparator 79 and is utilized to increase or decrease the set point of the differential amplifier and comparator'79 so that the effective voltage E across the input of the differential amplifier and comparator 79 is equivalent to the original calibration voltage E increased or decreased by density shift voltage E as dialed into the override exposure control 12 through switch 99.
  • a photographic process timer having initially calibrated means for controlling the illumination time of exposure lamps utilized in photographic processes, said means being calibrated according to the operating conditions at the time of calibration the improvement comprising an exposure override control apparatus electrically connected thereto which modifies the duration of the timing cycles for the lamps in the same percentage to compensate for a change in operating conditions whereby the initial calibration of the means for controlling the illumination time of the exposure lamp can be maintained constant even though at least one of the initial operating conditions have changed.
  • said exposure override control apparatus comprises means for logarithmically varying the illumination time duration for each timing cycle in the same percentage.
  • said resistance network comprises resistors connected in series.
  • each resistor is determined according to the formula R R, (E /E wherein R, is the control resistance to ground, R, is the total resistance of the serially connected resistance network, E is the total voltage across the resistance network and E is the control voltage calculated from the antilogarithm of the ratio of the total voltage across the impedance network ratioed to the effective voltage to be obtained, the effective voltage being the difference between the total voltage and the control voltage.
  • a photographic process timer having a plurality of time unit resistances and at least one comparison means, the time unit resistances being linearly variable and utilized to determine the duration of energization of exposure lamps used in photographic processes and the comparison means being utilized to determine when the time duration controlled by the time unit resistances has been achieved, the improvement comprismg a logarithmically variable exposure override control apparatus connected to saidtcomparison means to vary the time duration controlled by the time unit resistances according to the setting of the exposure override control apparatus.
  • said exposure override control apparatus comprises means for logarithmically varying the illumination time duration for each timing cycle in the same percentage.
  • said resistance network comprises resistors, serially connected.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Of Exposure In Printing And Copying (AREA)
  • Light Sources And Details Of Projection-Printing Devices (AREA)
US00316672A 1972-12-20 1972-12-20 Exposure override control Expired - Lifetime US3828226A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US00316672A US3828226A (en) 1972-12-20 1972-12-20 Exposure override control
DE2361559A DE2361559A1 (de) 1972-12-20 1973-12-11 Photoprozess-timer
GB5884573A GB1416610A (en) 1972-12-20 1973-12-19 Timer
BE139100A BE808902A (fr) 1972-12-20 1973-12-20 Commande preponderante d'exposition
JP48141983A JPS49110346A (xx) 1972-12-20 1973-12-20

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00316672A US3828226A (en) 1972-12-20 1972-12-20 Exposure override control

Publications (1)

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US3828226A true US3828226A (en) 1974-08-06

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US00316672A Expired - Lifetime US3828226A (en) 1972-12-20 1972-12-20 Exposure override control

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US (1) US3828226A (xx)
JP (1) JPS49110346A (xx)
BE (1) BE808902A (xx)
DE (1) DE2361559A1 (xx)
GB (1) GB1416610A (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4498140A (en) * 1982-06-02 1985-02-05 Chesley F. Carlson Automated self calibrating exposure computer
US6778696B1 (en) * 2000-10-12 2004-08-17 Eastman Kodak Company Integrated traditional and digital photographic processing system with exchanged feedback control

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2024438B (en) * 1978-06-30 1983-04-27 Canon Kk Electrophotographic copier

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3293033A (en) * 1960-01-18 1966-12-20 Pako Corp Method for controlling explosure in a photographic color printer
US3672767A (en) * 1970-07-15 1972-06-27 Carlson Co Chesley F Photo process timer
US3724954A (en) * 1972-01-14 1973-04-03 Photo Electronics Corp Logarithmic circuit with automatic compensation for variations in conditions of operations

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3293033A (en) * 1960-01-18 1966-12-20 Pako Corp Method for controlling explosure in a photographic color printer
US3672767A (en) * 1970-07-15 1972-06-27 Carlson Co Chesley F Photo process timer
US3724954A (en) * 1972-01-14 1973-04-03 Photo Electronics Corp Logarithmic circuit with automatic compensation for variations in conditions of operations

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4498140A (en) * 1982-06-02 1985-02-05 Chesley F. Carlson Automated self calibrating exposure computer
US6778696B1 (en) * 2000-10-12 2004-08-17 Eastman Kodak Company Integrated traditional and digital photographic processing system with exchanged feedback control

Also Published As

Publication number Publication date
DE2361559A1 (de) 1974-06-27
GB1416610A (en) 1975-12-03
BE808902A (fr) 1974-04-16
JPS49110346A (xx) 1974-10-21

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