Method and apparatus for subject image tracking in high definition film-to-video color correction

• US 5,387,929 A
• Filed: 11/20/1992
• Issued: 02/07/1995
• Est. Priority Date: 11/20/1992
• Status: Expired due to Term

• Current Assignee: Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Collier, David C.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US07/979,170
• Time in Patent Office: 809 Days
• Field of Search: 358/54, 358/214, 358/500, 358/517, 358/518, 358/519, 358/520, 358/504, 358/139, 358/10
• US Class Current: 348/97
• CPC Class Codes: H04N 9/11 Scanning of colour motion picture films, e.g. for telecine
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

A subject image being electronically transferred from a first medium to a second medium is accomplished through tone scale tracking. Three monochromatic channels representing the subject image are generated from the first medium. In a preferred embodiment, an image processing system provides color correction for each channel by compensating for film and video characteristics that cause a degradation of color from the original subject image. Calibration of the system is provided by means for an operator to specify tone densities for the second medium that correlate to signal levels derived from the first medium for each channel. The image processing system tracks the tone densities calibrated to provide enhanced film masking. The image processing system also performs characteristic curve processing in accordance with a Hurter-Driffield (HD) curve. A characteristic curve interface is provided allowing an operator to place the subject image on the characteristic curve so that the image processing system tracks the location of the subject image on the curve.

Claims

1. A method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium, said method comprising the steps of:

generating a plurality of monochromatic channels from said subject image recorded on said first medium wherein each of said monochromatic channels represents a complementary color such that said plurality of monochromatic channels comprise a polychromatic image of said subject image;

selecting a white level for said second medium by specifying a first input amplitude for each monochromatic channel such that said first input amplitude corresponds to a first tone on said second medium;

selecting a black level for said second medium by specifying a second input amplitude for each monochromatic channel such that said second input amplitude corresponds to a second tone on said second medium;

converting said subject image for each monochromatic channel into a logarithmic domain;

providing a Hurter-Driffield (HD) characteristic curve for each logarithmic converted monochromatic channel, said HD characteristic curve depicting density of said subject image on said first medium on a vertical axis and relative logarithmic exposure of said subject image recorded on said first medium on a horizontal axis;

specifying a dynamic range for said subject image for each monochromatic channel on said relative logarithmic exposure axis;

mapping said white and black levels onto said dynamic range specified on said relative logarithmic exposure axis;

correcting said subject image in each monochromatic channel in accordance with said HD characteristic curves based on said dynamic range specified, said white and black levels being tracked through correction with said HD characteristic curve;

exponentiating said subject image for each corrected monochromatic channel out of said logarithmic domain while tracking said white and black levels; and

placing said subject image for each monochromatic channel into an output range compatible with said second medium in accordance with said white and black levels.

2. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 wherein the step of specifying a dynamic range on said relative logarithm exposure axis comprises the steps of:

defining a subject black level on said relative logarithm exposure axis of said characteristic curve corresponding to a base exposure level that said subject image was recorded on said first medium; and

defining a subject contrast on said characteristic curve, said subject contrast defining said dynamic range on said relative logarithm exposure axis of said characteristic curve corresponding to a subject contrast of said subject image as recorded on said first medium.

3. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 wherein the steps of selecting said white and black levels further comprises the steps of:

providing a calibration interface comprising a black level slider and a white level slider for each of said monochromatic channels;

adjusting said white level slider so as to select said white level, said white level slider specifying said first input amplitude for each monochromatic channel;

adjusting said black level slider so as to select said black level, said black level slider specifying said second input amplitude for each monochromatic channel.

4. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 2 wherein the steps of defining said subject black level and said subject contrast further comprises the step of providing a characteristic curve interface comprising a subject black and subject range controls for each monochromatic channel, said subject black and said subject range controls providing a means to place said subject image anywhere within said relative logarithm exposure axis of said HD characteristic curve.

5. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 further comprising the step of providing film masking when said subject image is in said logarithmic domain, said film masking compensating in each monochromatic channel for crosstalk among polychromatic color emulsions contained within the first medium.

6. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 wherein the step of placing each of said monochromatic channels into an output range compatible with said second medium comprises the steps of:

selecting a monochromatic channel as a reference channel from said plurality of monochromatic channels;

specifying an output white level for said reference channel equaling said white level for said reference channel at said first input amplitude selected;

specifying an output black level for said green channel equaling said black level for said green channel at said second input amplitude selected; and

adjusting output white and black levels for each remaining monochromatic channels so as to allow said output white and black levels for said remaining monochromatic channels to be specified by a relative relationship of a subject black point on a log exposure axis of said remaining monochromatic channels to a subject black point on a log exposure axis of said reference channel.

7. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 6 wherein selecting a monochromatic channel as a reference channel from said plurality of monochromatic channels comprises the step of selecting a green channel as said reference channel.

8. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 further comprising the step of balancing a gray scale of said subject image for each monochromatic channel such that said gray scale is relatively linear and uniform in a central tone region corresponding to a linear portion of said HD characteristic curve.

9. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 8 wherein the step of balancing a gray scale further comprises the step of adjusting gamma values for each monochromatic channel.

10. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 8 wherein the step of balancing a gray scale further comprises the step of adjusting toe values for each monochromatic channel.

11. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 10 wherein the step of adjusting toe values further comprises the step of stepping up said subject image on a toe portion of said HD characteristic curve.

12. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 8 wherein the step of balancing a gray scale further comprises the step of adjusting shoulder values for each monochromatic channel.

13. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 12 wherein the step of adjusting said shoulder values further comprises the step of placing said subject image on a shoulder portion of said characteristic curve.

14. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 further comprising the steps of:

providing a film masking matrix defining crosstalk among polychromatic color emulsions in each monochromatic channel within said first medium;

providing video cross talk matrix defining electronic cross talk and non-linear responses within said subject image;

manipulating said film masking matrix and said video cross talk matrix so as to globally correct said colors and saturations in said subject image.

15. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 wherein said first medium comprises motion picture film.

16. The method for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 1 wherein said second medium comprises high definition video.

17. A method for tracking a subject image recorded on film and being electronically transferred to high definition video, said method comprising the steps of:

generating a plurality of monochromatic channels from said subject image recorded on said film wherein each of said monochromatic channels represents a complementary color such that said plurality of monochromatic channels comprise a polychromatic image of said subject image;

selecting a white level for said high definition video by specifying a first input amplitude for each monochromatic channel such that said first input amplitude corresponds to a first tone on said high definition video;

selecting a black level for said high definition video by specifying a second input amplitude for each monochromatic channel such that said second input amplitude corresponds to a second tone on said high definition video;

converting said subject image for each monochromatic channel into a logarithmic domain;

providing a Hurter-Driffield (HD) characteristic curve for each logarithmic converted monochromatic channel, said HD characteristic curve depicting density of said subject image on said film on a vertical axis and relative logarithmic exposure of said subject image recorded on said film on a horizontal axis;

specifying a dynamic range for said subject image for each monochromatic channel on said relative logarithmic exposure axis;

mapping said white and black levels onto said dynamic range specified on said relative logarithmic exposure axis;

defining a subject black level on said relative logarithmic exposure axis of said characteristic curve corresponding to a base exposure level that said subject image was recorded on said film;

defining a subject contrast on said relative logarithm exposure axis of said characteristic curve, said subject contrast defining said dynamic range corresponding to a subject contrast of said subject image as recorded on said film;

correcting said subject image in each monochromatic channel in accordance with said HD characteristic curve based on said dynamic range specified, said white and black levels being tracked through correction with said HD characteristic curve;

exponentiating said subject image for each corrected monochromatic channel out of said logarithmic domain while tracking said white and black levels;

balancing a gray scale of said subject image for each monochromatic channel such that said gray scale is relatively linear and uniform in a central tone region corresponding to a linear portion of said HD characteristic curve;

selecting a green monochromatic channel as a reference channel from said plurality of monochromatic channels;

specifying an output white level for said green channel equaling said white level for said green channel at said first input amplitude selected;

specifying an output black level for said green channel equaling said black level for said green channel at said second input amplitude selected; and

adjusting output white and black levels for each remaining monochromatic channels such that said remaining monochromatic channels float relative to said green monochromatic channel.

18. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 wherein the steps of selecting said white and black levels further comprises the steps of:

providing a calibration interface comprising a black level slider and a white level slider for each of said monochromatic channels;

adjusting said white level slider so as to select said white level, said white level slider specifying said first input amplitude for each monochromatic channel; and

adjusting said black level slider so as to select said black level, said black level slider specifying said second input amplitude for each monochromatic channel.

19. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 wherein the steps of defining said subject black level and said subject contrast further comprises the step of providing a characteristic curve interface comprising a subject black and subject range controls for each monochromatic channel, said subject black and said subject range controls providing a means to place said subject image anywhere within said relative logarithm exposure axis of said HD characteristic curve.

20. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 further comprising the step of providing film masking when said subject image is in said logarithmic domain, said film masking compensating in each monochromatic channel for crosstalk among polychromatic color emulsions contained within the first medium.

21. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 wherein the step of balancing a gray scale further comprises the step of adjusting gamma values for each monochromatic channel.

22. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 wherein the step of balancing a gray scale further comprises the step of adjusting toe values for each monochromatic channel.

23. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 22 wherein the step of adjusting toe values further comprises the step of placing said subject image on a toe portion of said HD characteristic curve.

24. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 17 wherein the step of balancing a gray scale further comprises the step of adjusting shoulder values for each monochromatic channel.

25. The method for tracking a subject image recorded on film and being electronically transferred to high definition video as claimed in claim 24 wherein the step of adjusting said shoulder values further comprises the step of placing said subject image on a shoulder portion of said characteristic curve.

26. An apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium, said apparatus comprising:

film scanner means for generating a plurality of monochromatic channels from said subject image recorded on said first medium wherein each of said monochromatic channels represents a complementary color such that said plurality of monochromatic channels comprise a polychromatic image of said subject image;

calibration means coupled to said film scanner means for calibrating said subject image of each monochromatic channel, said calibration means accepting each monochromatic channel, said calibration means comprising;

white level means for selecting a white level for said second medium by specifying a first input amplitude for each monochromatic channel such that said first input amplitude corresponds to a first tone on said second medium, and

black level means for selecting a black level for said second medium by specifying a second input amplitude for each monochromatic channel such that said second input amplitude corresponds to a second tone on said second medium,

logarithmic conversion means for converting said subject image for each calibrated monochromatic channel into a logarithmic domain;

Hurter-Driffield (HD) characteristic curve means for generating a (HD) characteristic curve for each logarithmic converted monochromatic channel, said HD characteristic curve depicting density of said subject image on said first medium on a vertical axis and relative logarithmic exposure of said subject image recorded on said first medium on a horizontal axis;

dynamic range means for specifying a dynamic range on said relative logarithmic exposure axis identifying said subject image for each monochromatic channel;

mapping means for mapping said white and black levels onto said dynamic range specified on said relative logarithmic exposure axis;

film correction means for correcting said subject image in each monochromatic channel in accordance with said HD characteristic curve based on said dynamic range specified, said white and black levels being tracked through correction with said HD characteristic curve;

exponentiating conversion means for converting said subject image for each film corrected monochromatic channel out of said logarithmic domain while tracking said white and black levels; and

output range means for placing said subject image for each monochromatic channel into an output range compatible with said second medium in accordance with said white and black levels.

27. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 wherein said dynamic range means comprises:

subject black level means for defining a subject black level on said relative logarithm exposure axis of said HD characteristic curve corresponding to a base exposure level that said subject image was recorded on said first medium; and

subject contrast means for defining a subject contrast on said characteristic curve, said subject contrast defining said dynamic range on said relative logarithm exposure axis of said HD characteristic curve corresponding to a subject contrast of said subject image as recorded on said first medium.

28. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 27 wherein said dynamic range means further comprises a characteristic curve interface comprising subject black and subject range controls for each monochromatic channel, said subject black and said subject range controls placing said subject image anywhere within said relative logarithm exposure axis of said HD characteristic curve.

29. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 wherein said calibration means further comprises calibration interface means comprising a black level slider and a white level slider for each of said monochromatic channels for specifying said white and black levels such that adjusting said white level slider for each monochromatic channel at said first input amplitude selects said white level, and adjusting said black level slider for each monochromatic channel at said second input amplitude selects said black level.

30. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 further comprising film masking means for compensating in each monochromatic channel for crosstalk among polychromatic color emulsions contained within the first medium when said subject image is in said logarithmic domain.

31. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 wherein said output range means further comprises a means for selecting a green monochromatic channel as a reference channel from said plurality of monochromatic channels, and specifying an output white level for said green channel equaling said white level for said green channel at said first input amplitude selected, said output range means specifies an output black level for said green channel equaling said black level for said green channel at said second input amplitude selected, and adjusts output white and black levels for each remaining monochromatic channels such that said remaining monochromatic channels float relative to said green monochromatic channel.

32. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 further comprising gray scale balancing means for balancing a gray scale of said subject image for each monochromatic channel such that said gray scale is relatively linear and uniform in a central tone region corresponding to a linear portion of said HD characteristic curve.

33. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 32 wherein said gray scale balancing means further includes means for adjusting gamma values for each monochromatic channel.

34. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 32 wherein said gray scale balancing means further includes means for adjusting toe values for each monochromatic channel.

35. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 32 wherein said gray scale balancing means further includes means for placing said subject image on a toe portion of said HD characteristic curve.

36. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 32 wherein said gray scale balancing means further includes means for adjusting shoulder values for each monochromatic channel.

37. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 36 wherein said gray scale balancing means places said subject image on a shoulder portion of said characteristic curve.

38. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 wherein said first medium comprises motion picture film.

39. The apparatus for tracking a subject image recorded on a first medium and being electronically transferred to a second medium as claimed in claim 26 wherein said second medium comprises high definition video.