Method of digital processing for digital cinema projection of tone scale and color

1. A method for processing a sequence of digital image signals in order to match the appearance of a particular print film when the image signals are displayed, said method comprising the steps of:

converting the digital image signals into signal values in print material analytical dye amount space where the signal values are proportional to a print dye set corresponding to the particular print film; and

converting the signal values in the print material analytical dye amount space into output values suitable for a display device.

2. A method as claimed in claim 1 wherein the signal values in the print material analytical dye amount space are corrected for viewing conditions.

3. The method as claimed in claim 2 wherein the step of correcting the signals for viewing conditions includes correcting for at least one of printing flare, gamma, contrast ratio and neutrality.

4. A method as claimed in claim 1 wherein the step of converting the signal values in the print material analytical dye amount space into output values further includes the steps of:

converting the signal values in the print material analytical dye amount space into a perceptual color space based upon a chosen illuminant for display of the image signals; and

converting the signals in the perceptual color space into output values suitable for the display device.

5. A method as claimed in claim 1 further including the step of re-mapping any output values that are out of the gamut of the display device.

6. The method as claimed in claim 1 wherein the display device is a digital projector.

7. The method as claimed in claim 1 wherein the steps are performed by a 3D look up table based upon a tetrahedral interpolation.

8. A method for processing a sequence of digital image signals in order to match the appearance of a particular print film when the image signals are displayed on a digital display device, said method comprising the steps of:

providing the sequence of digital image signals;

converting the digital image signals into signal values in print film analytical dye amount space where the signal values are proportional to a print film dye set corresponding to the particular print film;

converting the signal values in the print film analytical dye amount space into signals in a perceptual color space based upon a chosen illuminant for display of the image signals;

converting the signals in the perceptual color space into output values suitable for a digital display device;

re-mapping any output values that are out of the gamut of the digital display device into re-mapped output values; and

providing the output values, including any re-mapped values, to the digital display device.

9. The method as claimed in claim 8 further comprising the steps of:

normalizing the re-mapped display values in a linear conversion stage, thereby providing normalized display values;

rescaling the normalized display values to a bit depth of the display device, thereby providing rescaled display values;

applying an inverse gamma function to the rescaled display values, thereby providing gamma corrected display values; and

providing the gamma corrected display values to the digital display device.

10. The method as claimed in claim 8 wherein the digital display device is a digital projector.

11. The method as claimed in claim 8 wherein the digital display device is a CRT monitor.

12. The method as claimed in claim 8 wherein the step of providing the output values, including any re-mapped values, to the digital display device comprises storing the output values on a storage medium that is subsequently provided to the digital display device.

13. The method as claimed in claim 8 wherein the step of providing the sequence of image signals comprises scanning a motion picture film with a motion picture film scanner in order to generate print density image signals.

14. The method as claimed in claim 13 wherein the step of converting the image signals into the print film analytical amount space comprises mapping the print density image signals through a print type transfer curve to obtain analytical dye amounts, wherein the print type transfer curve is constructed by

providing density log exposure curves for the motion picture print film;

converting the density log exposure curves into print film analytical dye amounts in the print film analytical dye amount space;

correcting the signals in the print film analytical dye amount space for viewing conditions; and

forming a print type transfer curve from the corrected signals.

15. The method as claimed in claim 14 wherein the step of correcting the signals includes correcting for at least one of printing flare, gamma, contrast ratio and neutrality.

16. The method as claimed in claim 8 further comprising the steps of:

normalizing the re-mapped display values in a linear conversion stage, thereby providing normalized display values;

rescaling the normalized display values to a bit depth of the digital display device, thereby providing rescaled display values;

applying an inverse gamma function to the resealed display values, thereby providing gamma corrected display values; and

providing the gamma corrected display values to the digital display device.

17. A method for processing a sequence of digital image signals in order to match the tone scale and color of a particular motion picture print film when the image signals are digitally projected, said method comprising the steps of:

scanning motion picture film to provide the sequence of digital image signals;

converting the image signals through a tone scale curve into signal values in print film analytical dye amount space where the signal values are proportional to a print film dye set corresponding to the particular motion picture print film;

converting the signal values in analytical dye amount space into signals in a perceptual color space based upon a chosen illuminant for display of the image signals;

converting the signals in the perceptual color space into output values suitable for a digital projector;

re-mapping any output values that are out of the gamut of the digital projector; and

providing the re-mapped values to the digital projector.

18. The method as claimed in claim 17 wherein the step of providing the output values, including any re-mapped values, to the digital projector comprises storing the output values on a storage medium that is subsequently provided to the digital projector.

19. The method as claimed in claim 17 wherein the step of converting the image signals into print film analytical amount space comprises mapping the image signals through a print type transfer curve to obtain print film analytical dye amounts, wherein the print type transfer curve is constructed by

providing density log exposure curves for the motion picture print film;

converting the density log exposure curves into print film analytical dye amounts in the print film analytical dye amount space;

correcting the signals in print film analytical dye amount space for viewing conditions; and

forming a print type transfer curve from the corrected signals.

20. The method as claimed in claim 19 wherein the step of correcting the signals includes correcting for at least one of printing flare, gamma, contrast ratio and neutrality.

21. A transformation for transforming a sequence of digital image signals in order to match the appearance of a particular print film when the image signals are displayed by a digital display device, said transformation being modeled by (a) conversion of the digital image signals into signal values in the print film analytical dye amount space where the signal values are proportional to a dye set corresponding to the particular and (b) conversion of the signal values in the print film analytical dye amount space into output values suitable for the digtal display device.

22. The transformation as claimed in claim 21 wherein the modeled conversions are performed by a 3-dimensional look up table.

23. The transformation as claimed in claim 22 wherein the 3-dimensional look up table is based upon a tetrahedral interpolation.

24. A 3-dimensional look up table populated with input and output values that achieve the transformation modeled in claim 21 .

25. The 3-dimensional look up table as claimed in claim 24 wherein the look up table is based upon a tetrahedral interpolation.

26. The transformation as claimed in claim 21 wherein the digital display device is a digital projector.

27. A transformation as claimed in claim 21 wherein the signal values in the print film analytical dye amount space are corrected for viewing conditions.

28. The transformation as claimed in claim 27 wherein the correction for viewing conditions includes correcting for at least one of printing flare, gamma, contrast ratio and neutrality.

29. The transformation as claimed in claim 21 wherein the conversion of the signal values in the print film analytical dye amount space into output values is further modeled by:

converting the signal values in the print film analytical dye amount space into a perceptual color space based upon a chosen illuminant for display of the image signals; and

converting the signals in the perceptual color space into output values suitable for a digital display device.

30. The transformation as claimed in claim 21 further including a re-mapping of any output values that are out of a gamut of the digital display device.