Computerized video imaging system

Abstract

A computerized video imaging system is provided which includes a target mount for supporting a target photographic transparency. A lamphouse is positioned to pass light through the transparency and includes light sources for a set of primary colors. An image sensor is positioned to receive light passing from the lamphouse through the transparency and generates video signals representing hue and intensity of the light. Image storage means are provided for storing color reference representations of the reference transparency. A color video monitor receives signals related to the reference representations and the target video signals. A computer interfaces with the light source and the image storage to calculate photographic color correction values for the target transparency.

What is claimed and desired to be secured by Letters Patent is as follows: 
     
       1. A computerized video imaging system comprising: (a) target mounting means for supporting a color photographic production target;   (b) lamphouse means positioned to illuminate said target and including light sources respectively of a set of primary colors, the intensities of light from said light sources being controllable individually and collectively in measurable amounts;   (c) an image sensor positioned to receive light from said lamphouse means as altered by interaction with said target and generating over a time cycle a set of color component production video signals which in combination represent the hue and intensity of light as altered by interaction with spatial regions of said target;   (d) image storage means storing color reference representations of a substantial area of a reference target, said reference representations being related to a reference balance of intensities of said light sources;   (e) color video monitor means operatively connected to said image sensor means and said image storage means, receiving signals related to said reference representations and said production video signals, reproducing at least a portion of a production image representative of said production target as illuminated by said lamphouse means and at least a portion of a reference image representative of said reference .[.transparency.]. .Iadd.target .Iaddend.as illuminated by said lamphouse means, with said light sources set to said reference balance;   (f) light source adjustment means for adjusting the intensities of light from said light sources, said adjustment means being adjusted until the color balance of said production image assumes a production balance wherein the color balance of said production image as viewed on said monitor means appears to match the color balance of said reference image as viewed on said monitor means; and   (g) computer means interfaced to said adjustment means and said image storage means and operative to calculate photographic color correction values for said production target which are representations respectively of the differences between the intensities of light from said light sources for said production balance and the intensities of light from said light sources for said reference balance.   
     
     
       2. A computerized video imaging system comprising; (a) target mounting means for supporting a target photographic transparency;   (b) lamphouse means positioned to pass light through said transparency and including light sources respectively of a set of primary colors, the intensities of light from said light sources being controllable individually and collectively in measurable amounts;   (c) an image sensor positioned to receive light passing from said lamphouse means through said transparency and generating over a time cycle a set of color component target video signals which in combination represent the hue and intensity of light received through spatial regions of said transparency;   (d) image storage means storing color reference representations of a substantial area of a reference transparency, said reference representations being related to a reference balance of intensities of said light sources;   (e) color video monitor means operatively connected to said image sensor means and said image storage means, receiving signals related to said reference representations and said target video signals, reproducing at least a portion of a target image representative of said target transparency as illuminated by said lamphouse means and at least a portion of a reference image representative of said reference transparency as illuminated by said lamphouse means with said light sources set to said reference balance;   (f) light source adjustment means for adjusting the intensities of light from said light sources, said adjustment means being adjusted until the color balance of said target image assumes a target balance wherein the color balance of said target image as viewed on said monitor means appears to match the color balance of said reference image as viewed on said monitor means; and   (g) computer means interfaced to said adjustment means and said image storage means and operative to calculate photographic color correction values for said target transparency which are representations respectively of the differences between the intensities of light from said light sources for said target balance and the intensities of light from said light sources for said reference balance.   
     
     
       3. A system as set forth in claim 2 wherein: (a) said monitor means is a .[.one.]. .Iadd.single, .Iaddend.color video monitor; and   (b) said system includes image timing means operative to cause the display of said portion of said target image and said portion of said reference image in substantially side-by-side relation on said video monitor.   
     
     
       4. A system as set forth in claim 2 wherein said light source adjustment means includes: (a) a neutral density control operable to control said light sources in unison; and   (b) a color balance control operable to adjust the balance of intensities of light from said light sources.   
     
     
       5. A system as set forth in claim .[.2.]. .Iadd.4 .Iaddend.wherein: (a) said color balance control includes a trackball device.   
     
     
       6. A system as set forth in claim 2 wherein: (a) said lamphouse means is an additive color lamphouse; and   (b) said light sources include controllable sources of red, green, and blue light.   
     
     
       7. A system as set forth in claim 2 wherein: (a) said image sensor is a solid state image sensor.   
     
     
       8. A computerized video imaging system comprising: (a) target mounting means for supporting a target photographic transparency;   (b) lamphouse means positioned to pass light through said transparency and including light sources respectively of a set of primary colors, the intensities of light from said light sources being controllable individually and collectively in measurable amounts;   (c) an image sensor positioned to receive light passing from said lamphouse means through said transparency and generating over a time cycle a set of color component video signals which in combination represent the hue and intensity of light received through spatial regions of said transparency;   (d) a set of analog to digital converters (ADC's) connected to said image sensor and operative over said time cycle to convert said video signals to target digital representations of color .[.components.]. .Iadd.component .Iaddend.intensities of said spatial regions of said transparency;   (e) an image memory for the storage of reference digital representations of color component intensities of a substantial area of a reference transparency, said reference digital representations being related to a reference balance of intensities of light from said light sources;   (f) digital to analog converter (DAC) means operatively connected to said ADC's and said image memory and converting over said time cycle said target digital representations and said reference digital representations to respective display color component video signals;   (g) color video monitor means connected to said DAC means, receiving said display color component video signals, and reproducing at least a portion of a target image representative of said target transparency as illuminated by said lamphouse means and at least a portion of a reference image representative of said reference transparency as illuminated by said lamphouse means with said light sources set to said reference balance;   (h) image timing means operatively connected to said image sensor, said ADC's, said image memory, and said monitor means and controlling said time cycle thereof;   (i) light source adjustment means for adjusting the intensities of light from said light sources, said adjustment means being adjusted until the color balance of said target image assumes a target balance wherein the color balance of said target image as viewed on said monitor means appears to match the color balance of said reference image as viewed on said monitor means; and   (j) computer means interfaced to said adjustment means, said ADC's, and said image memory and operative to calculate photographic color correction values for said target transparency which are representations respectively of the differences between the intensities of light from said light sources for said target balance and the intensities of light from said light sources for said reference balance.   
     
     
       9. A system as set forth in claim 8 wherein: (a) said monitor means is .[.one.]. .Iadd.a single, .Iaddend.color video monitor; and   (b) said image timing means is operative to cause the display of said portion of said target image and said portion of said reference image in substantially side-by-side relation on said video monitor.   
     
     
       10. A system as set forth in claim 8 wherein said light source adjustment means includes: (a) a neutral density control operable to control said light sources in unison; and   (b) a color balance control operable to adjust the balance of intensities of light from said light sources.   
     
     
       11. A system as set forth in claim 10 wherein: (a) said color balance control includes a color balance control operator movable in two dimensions; and   (b) said color balance control is arranged as a vector length color control wherein the direction of movement of said operator corresponds to the dominant hue of the color balance of light from said light sources which is affected by said movement and the vector resultant length of said movement corresponds to the degree of change of said dominant hue.   
     
     
       12. A system as set forth in claim 10 wherein: (a) said color balance control includes a trackball device.   
     
     
       13. A system as set forth in claim 10 wherein: (a) said neutral density control includes a trackwheel device.   
     
     
       14. A system as set forth in claim 8 wherein: (a) said lamphouse means is an additive color lamphouse; and   (b) said light sources include controllable sources of red, green and blue light.   
     
     
       15. A system as set forth in claim 8 wherein: (a) said image sensor is a solid state image sensor.   
     
     
       16. A system as set forth in claim 8 including: (a) look-up table memory means connected to .[.the.]. .Iadd.a .Iaddend.digital side of said DAC means, said look-up table memory means modifying the binary values of said target digital representations and said reference digital representations prior to conversion by said DAC means.   
     
     
       17. A system as set forth in claim 16 wherein: (a) said look-up table memory means is a look-up table read/write memory; and   (b) said look-up table memory is interfaced to said computer means whereby look-up table values stored in said look-up table memory can be selectively communicated thereto by said computer means.   
     
     
       18. A system as set forth in claim 16 wherein: (a) said target transparency is a photographic negative;   (b) said reference transparency is a photographic negative; and   (c) said look-up table means has stored therein look-up table values for modifying the binary values of said target digital representations and said reference digital representations such that said DAC means causes said monitor means to display photographically positive images of said negatives.   
     
     
       19. A method of color analyzing photographic transparencies comprising the steps of: (a) illuminating an image sensor through a reference color photographic transparency by light from a lamphouse including controllable light sources respectively of a set of primary colors;   (b) generating over a time cycle a set of color component reference video signals by means of said image sensor, said reference video signals in combination representing the hue and intensity of light received through spatial regions of said reference transparency as illuminated by said lamphouse with said light sources set to a reference balance of light intensities;   (c) storing in an image storage means reference image representations of said reference video signals which may be reconstructed to reproduce a reference image of said reference transparency as illuminated by said lamphouse set to said reference balance;   (d) illuminating said image sensor through a target color photographic transparency by light from said lamphouse;   (e) generating over said time cycle a set of color component target video signals by means of said image sensor, said target video signals in combination representing the hue and intensity of light received .[.thorugh.]. .Iadd.through .Iaddend.spatial regions of said target transparency as illuminated by said lamphouse;   (f) displaying on color video monitor means a reference image from the reference image representations stored in said image storage means;   (g) displaying on said color video monitor means a target image from target representations of said target video signals;   (h) visually comparing the displayed target color balance of said target image with the displayed reference color balance of said reference image;   (i) adjusting the color balance of the intensities of light from said light sources of said lamphouse using color adjustment means until a target balance of the light intensities from said light sources causes said target color balance to appear to match said reference color balance as viewed on said color video monitor means; and   (j) calculating a set of color correction values which are representations respectively of the differences between the intensities of light from said light sources for said target balance and the intensities of light from said light sources for said reference balance.   
     
     
       20. A method as set forth in claim 19 including the step of: (a) printing said color correction values as numbers on paper by means of a printer.   
     
     
       21. A method as set forth in claim 19 including the step of: (a) storing binary representations of said color correction values on a magnetic medium.   
     
     
       22. A method as set forth in claim 19 including the step of: (a) printing said color correction values as a bar code on paper by means of a bar code printer.   
     
     
       23. A method as set forth in claim 19 wherein each of said illuminating steps includes the step of: (a) illuminating said image sensor through a respective transparency by light from an additive lamphouse including controllable sources of red, green, and blue light.   
     
     
       24. A method as set forth in claim 19 wherein said generating steps each includes the step of: (a) generating the respective sets of video signals using a solid state image sensor.   
     
     
       25. A method as set forth in claim 19 including the steps of: (a) converting over said time cycle said set of color component reference video signals to a respective set of reference digital representations.   (b) storing said reference digital representations in said image storage means, said image storage means being a read/write image memory;   (c) converting over said time cycle said set of color component target video signals to a respective set of target digital representations; and   (d) converting said set of reference digital representations and said set of target digital representations respectively to a set of reference display video signals and a set of target display video signals for displaying said reference image and said target image on said color video monitor means.   
     
     
       26. A method as set forth in claim 25 including the step of: (a) modifying said reference digital representations and said target digital representations according to look-up table values stored in a look-up table memory prior to the conversion of said digital representations respectively to said display video signals.   
     
     
       27. A method as set forth in claim 26 wherein said modifying step includes the step of: (a) storing selected sets of said look-up table values in said look-up table memory, said look-up table memory being a read/write look-up table memory.   
     
     
       28. A method of color analyzing photographic images comprising the steps of: (a) illuminating an image sensor by light from a lamphouse which has been altered by interaction with a reference color photographic target, said lamphouse including controllable light sources respectively of a set of primary colors;   (b) generating over a time cycle a set of color component reference video signals by means of said image sensor, said reference video signals in combination representing the hue and intensity of light altered by spatial regions of said reference target as illuminated by said lamphouse with said light sources set to a reference balance of light intensities;   (c) storing in an image storage means reference image representations of said reference video signals which may be reconstructed to reproduce a reference image of said reference target as illuminated by said lamphouse set to said reference balance;   (d) illuminating said image sensor by light from said lamphouse which has been altered by interaction with a production color photographic target;   (e) generating over said time cycle a set of color component production video signals by means of said image sensor, said production video signals in combination representing the hue and intensity of light altered by spatial regions of said production target as illuminated by said lamphouse;   (f) displaying on color video monitor means a reference image from the reference image representations stored in said image storage means;   (g) displaying on said color video monitor means a production image from production representations of said production video signals;   (h) visually comparing the displayed production color balance of said production image with the displayed reference color balance of said reference image;   (i) adjusting the color balance of the intensities of light from said light sources of said lamphouse using color adjustment means until a production balance of the light intensities from said light sources causes said production color balance to appear to match said reference color balance .[.is.]. .Iadd.as .Iaddend.viewed on said color video monitor means; and   (j) calculating a set of color correction values which are representations respectively of the differences between the intensities of light from said light sources for said production balance and the .[.intesities of light from sid.]. .Iadd.intensities of light from said .Iaddend.light sources for said reference balance. .Iadd.   
     
     
       29.  A computerized video imaging system comprising: (a) target mounting means for supporting a color photographic target;   (b) light source means positioned to illuminate said target;   (c) an image sensor positioned to receive light from said light source means as altered by interaction with said target and generating over a time cycle a set of color component video signals which in combination represent the hue and intensity of light from said light source means as altered by interactions with spatial regions of said target;   (d) image storage means storing color representations of an image;   (e) a color video display device, having a video screen, operatively connected to said image sensor means and said image storage means, and operative to display images derived from video signals received from said image sensor means and said image storage means; and   (f) control means having said image sensor means, said image storage means, and said video display device connected thereto; said control means being operative to recall a first image from said image storage means and cause the display of at least a portion of said first image on said screen of said video display device and to cause at least a portion of a second image sensed by said image sensor means to be displayed on said screen of said video display device substantially simultaneously with the display of said first image..Iaddend. .Iadd.30. A system as set forth in claim 29 including:   (a) color balance adjustment means for adjusting a second color balance of said second image in comparison to a first color balance of said first image, as displayed on said video display device..Iaddend. .Iadd.31. A system as set forth in claim 30 wherein:   (a) said control means has said color balance adjustment means and said image storage means connected thereto and is operative to calculate photographic color correction values for said second image which are representations respectively of the difference between said second color balance before adjustment of said adjustment means and said second color   
     
     
        balance after adjustment of said adjustment means..Iaddend. .Iadd.32.  A computerized video imaging system comprising: (a) target mounting means for supporting a color photographic target;   (b) light source means positioned to illuminate said target;   (c) an image sensor positioned to receive light from said light source means as altered by interaction with said target and generating over a time cycle a set of color component video signals which in combination represent the hue and intensity of light from said light source means as altered by interactions with spatial regions of said target;   (d) image storage means storing color representations of an image;   (e) a first color video display device operatively connected to said image storage means to display a first image stored in said image storage means;   (f) a second color video display device operatively connected to said image sensor means to display a second image derived from a video signal received from said image sensor means; and   (g) control means having said image sensor means, said image storage means, and said first and second video display devices connected thereto; said control means being operative to recall a first image from said image storage means and cause the display of at least a portion of said first image on said first video display device and to cause at least a portion of a second image sensed by said image sensor means to be displayed on said second video display device substantially simultaneously with the display of said first image on said first video display device..Iaddend. .Iadd.33. A system as set forth in claim 32 including:   (a) color balance adjustment means for adjusting a second color balance of said second image in comparison to a first color balance of said first image, as displayed on said first video display device..Iaddend. .Iadd.34. A system as set forth in claim 33 wherein:   (a) said control means has said color balance adjustment means and said image storage means connected thereto and is operative to calculate photographic color correction values for said second image which are representations respectively of the difference between said second color balance before adjustment of said adjustment means and said second color   
     
     
        balance after adjustment of said adjustment means..Iaddend. .Iadd.35.  A method of comparing color images comprising the steps of: (a) converting a first color image having a first color balance to a first color video signal;   (b) storing said first video signal in video signal storage means;   (c) recalling said first video signal and applying said first video signal to color video display means in such a manner as to display said first color image on a first portion of said video display means;   (d) converting a second color image having a second color balance to a second color video signal;   (e) applying said second video signal to said video display means in such a manner as to display said second color image on a second portion of said video display means simultaneously with the display of said first image;   (f) comparing said second color balance with said first color balance; and   (g) changing the relative color balance of said color images..Iaddend. .Iadd.36. A method as set forth in claim 35 including the steps of:   (a) converting said first image to said first video signal by video conversion means; and   (b) converting said second image to said second video signal by the same   
     
     
        video conversion means..Iaddend. .Iadd.37.  A method as set forth in claim 35 wherein said video display means is a video display including a single video screen, and including the steps of: a) displaying said first image on a first portion of said video screen; and   (b) displaying said second image on a second portion of said video screen..Iaddend. .Iadd.38. A method as set forth in claim 35 wherein said video display device includes a first video display device and a second video display device, and including the steps of:   (a) displaying said first image on said first video display device; and   (b) displaying said second image on said second video display   
     
     
        device..Iaddend. .Iadd.39.  A method as set forth in claim 35 including the steps of: (a) providing video conversion means to convert said first and second images respectively to said first and second video signals;   (b) providing color balance adjustment means operatively connected between said video conversion means and said video display device; and   (c) adjusting said color balance adjustment means such that said second color balance changes in relation to said first color balance as viewed on said video display device..Iaddend. .Iadd.40. A method as set forth in claim 39 including the step of:   (a) adjusting said color balance adjustment means until said second color balance appears to match said first color balance as viewed on said video display device..Iaddend. .Iadd.41. A method as set forth in claim 39 including the step of:   (a) measuring the difference between said second color balance before said adjusting step and said second color balance after said adjusting   
     
     
        step..Iaddend. .Iadd.42.  A method of color analyzing photographic images comprising the steps of: (a) converting a first color image having a first color balance to a first color video signal;   (b) storing said first video signal in video signal storage means;   (c) recalling said first video signal and applying said first video signal to color video display means in such a manner as to display said first color image on a first portion of said video display means;   (d) converting a second color image having a second color balance to a second color video signal;   (e) applying said second video signal to said video display means in such a manner as to display said second color image on a second portion of said video display means simultaneously with the display of said first image; and   (f) analyzing said second color balance of said second image in relation to   
     
     
        said first color balance of said first image..Iaddend. .Iadd.43.  A method of color analyzing photographic images comprising the steps of: (a) illuminating image sensor means by light from light source means which has been altered by interaction with a first color photographic target;   (b) generating over a time cycle a first set of color component video signals by means of said image sensor means, said first video signals in combination representing the hue and intensity of light altered by spatial regions of said first target as illuminated by said light from said light source means;   (c) storing in an image storage means first image representations of said first video signals which may be reconstructed to reproduce a first image of said first target as illuminated by light from said light source means;   (d) illuminating said image sensor means by light from said light source means which has been altered by interaction with a second color photographic target;   (e) generating over said time cycle a second set of color component video signals by means of said image sensor means, said second video signals in combination representing the hue and intensity of light altered by spatial regions of said second target as illuminated by said light source means;   (f) displaying on a single screen of a color video display device said first image from the first image representations stored in said image storage means;   (g) displaying on said color video display device said second image by applying said second video signals to said color video display device; and   (h) visually comparing a displayed second color balance of said second image with a displayed first color balance of said first image..Iaddend.   
     
     
        .Iadd.44.  A method as set forth in claim 43 including the step of: (a) adjusting said second color balance of said second image in relation to said first color balance of said first as viewed on said color video display device..Iaddend. .Iadd.45. A method as set forth in claim 43 including the steps of:   (a) adjusting said second color balance of said second image until said second color balance appears to match said first color balance of said first image as viewed on said color video display device; and   (b) calculating a set of color correction values which are representations of the difference between said second color balance before said adjusting step and said second color balance after said adjusting step..Iaddend.   
     
     
        .Iadd.46.  A method of color analyzing photographic images comprising the steps of: (a) illuminating image sensor means by light from light source means which has been altered by interaction with a first color photographic target;   (b) generating over a time cycle a first set of color component video signals by means of said image sensor means, said first video signals in combination representing the hue and intensity of light altered by spatial regions of said first target as illuminated by said light from said light source means;   (c) storing in an image storage means first image representations of said first video signals which may be reconstructed to reproduce a first image of said first target as illuminated by light from said light source means;   (d) illuminating said image sensor means by light from said light source means which has been altered by interaction with a second color photographic target;   (e) generating over said time cycle a second set of color component video signals by means of said image sensor means, said second video signals in combination representing the hue and intensity of light altered by spatial regions of said second target as illuminated by said light source means;   (f) displaying on a first color video display device said first image from the first image representations stored in said image storage means;   (g) displaying on a second color video display device said second image by applying said second video signals to said second color video display device; and   (h) visually comparing a displayed second color balance of said second image with a displayed first color balance of said first image..Iaddend.   
     
     
        .Iadd.47.  A method as set forth in claim 46 including the step of: (a) adjusting said second color balance of said second image in relation to said first color balance of said first image as viewed respectively on   
     
     
        said second and first color video display devices..Iaddend. .Iadd.48.  A method as set forth in claim 46 including the steps of: (a) adjusting said second color balance of said second image until said second color balance appears to match said first color balance of said first image as viewed respectively on said second and first color video display devices; and   (b) calculating a set of color correction values which are representations of the difference between said second color balance before said adjusting step and said second color balance after said adjusting step..Iaddend.   
     
     
        .Iadd.49.  An apparatus for color analyzing photographic images comprising: (a) color image sensor means operative to generate video signals representing color images sensed by said image sensor means;   (b) video storage means connected to said image sensor means and selectively operable to store video signals representing at least a first color image;   (c) a color video display device having said image sensor means and said video storage means interfaced thereto, said video display device displaying images represented by video signals applied to said video display device;   (d) control means having said image sensor means, said video storage means, and said video display device connected thereto; said control means causing the generation of a second video signal representing a second color image sensed by said image sensor means;   (e) said control means causing the recalling of a first video signal representing said first image from said video storage means and the application of said first and second video signals to said video display device in such a manner that said first image is displayed on a first portion of said video display device and simultaneously said second image is displayed on a second portion of said video display device;   (f) said first image having a first color balance and said second image having a second color balance as viewed on said video display device; and   (g) said control means including color balance adjustment means operable to   
     
     
        vary said second color balance..Iaddend. .Iadd.50.  An apparatus as set forth in claim 49 wherein: (a) said video storage means is a digital storage means; and   (b) said apparatus includes digitizer means connected to said image sensor means and selectively operable to digitize video signals prior to storage of same in said digital storage means..Iaddend. .Iadd.51. An apparatus as set forth in claim 49 wherein said control means includes:   (a) color balance difference measuring means operable to measure the difference between said second color balance before operation of said color balance adjustment means and said second color balance after   
     
     
        operation of said color balance adjustment means..Iaddend. .Iadd.52.  An apparatus for color analyzing photographic images comprising: (a) image sensor means operative to generate video signals representing color images sensed by said image sensor means;   (b) video storage means connected to said image sensor means and selectively operable to store video signals representing at least a first color image;   (c) a first color video display device having said video storage means interfaced thereto and a second color video display device having said image sensor means interfaced thereto, said first and second video display devices displaying color images represented by video signals applied respectively to said video display devices;   (d) control means having said image sensor means, said video storage means, and said video display devices connected thereto; said control means causing the generation of a second video signal representing a second color image sensed by said image sensor means;   (e) said control means causing the recalling of a first video signal representing said first image from said video storage means and the simultaneous display of said first image on said first video display device and said second image on said second video display device;   (f) said first image having a first color balance and said second image having a second color balance as viewed respectively on said first and second video display devices; and   (g) said control means including color balance adjustment means operable to   
     
     
        vary said second color balance. .Iaddend. .Iadd.53.  A method of color analyzing photographic images comprising the steps of: (a) illuminating image sensor means by light provided by light source means and having a source color balance which is controllable, said light being altered by interaction with a photographic target;   (b) generating a video signal by said image sensor means which represents said light as altered by interaction with said target;   (c) applying said video signal to a color video display device to display thereon an image of said target as illuminated by said light source means; and   (d) varying said source color balance to thereby vary an image color balance of said image as displayed on said video display device..Iaddend.   
     
     
        .Iadd.54.  A method as set forth in claim 53 and including the steps of; (a) prior to varying said source color balance, setting said light source means to a reference color balance thereof;   (b) varying said source color balance to achieve a desired image color balance as displayed on said display means; and   (c) calculating photographic color correction values for said target which represent a difference between said reference color balance and said source color balance means after varying same to achieve said desired   
     
     
        image color balance..Iaddend. .Iadd.55.  An apparatus for color analyzing photographing images and comprising: (a) light source means providing light having a source color balance which is controllable;   (b) color image sensor means positioned in spaced relation to said light source means to receive light therefrom as altered by interaction with a photographic target and generate a video signal representing hues and intensities of said light as altered by interaction with spatial regions of said target;   (c) a color video display device interfaced with said image sensor means, having said video signal applied thereto, and displaying an image of said target as illuminated by said light source means; said image, as displayed, having an image color balance related to said source color balance whereby variation of said source color balance causes a corresponding variation in said image color balance; and   (d) color balance sensor means receiving said light from said light source means and generating a source color balance signal numerically representing said source color balance..Iaddend.