US 5,255,083 A · Digital color correction system and method

Abstract

A digital color correction system and method provide for color correction in a film-to-video signal conversion system. Film color correction is done by correcting incoming digitized film color signals (e.g. red, green and blue) according to film color correction parameters which represent film characteristics, such as film speed, gamma, and minimum and maximum film dye density. The film color correction parameters are used to sensitometrically convert the film color signals to video color signals according to a sensitometric film model, such as the Hurter-Driffield ("HD") characteristic curve. Video color correction is then performed upon the corrected film color signals according to video color correction parameters which represent video signal characteristics, such as hue and saturation, as well as a video color standard model, such as SMPTE 240M. Alternatively, separate signals representing the film or video color correction parameters can be encoded as separate data into the corrected or uncorrected color signals. This color correction or color correction parameter encoding can be done on a field-by-field, frame-by-frame or scene-by-scene basis, so that each resulting video field, frame or scene, respectively, is appropriately color corrected or contains its own specific color correction information.

Claims43

Dependent claims

A digital film color corrector for correcting a film color signal representing a portion of a colored optical film image in accordance with a plurality of color correction parameters associated with color film characteristics, the color corrector comprising:

a color signal port for receiving a digital film color signal representing a color film dye density;
a parameter signal port for receiving a plurality of digital film color correction signals representing a plurality of color film characteristics including film color masking;
and
film color corrector means for selectively correcting the received digital film color signal in accordance with the received digital film color correction signals, wherein the received digital film color signal is selectively modified to represent a color film exposure level.

1 more element

A digital color corrector for transforming a film color signal representing a portion of a colored optical film image into a video color signal in accordance with film and video color correction parameters associated with film and video signal characteristics, respectively, the color corrector comprising:

film color corrector means for receiving a plurality of digital film color correction signals, for receiving a digital film color signal, and for selectively correcting the received digital film color signal in accordance with the received digital film color correction signals, wherein the received digital film color correction signals represent a plurality of color film characteristics, the received digital film color signal represents a color film dye density, and the received digital film color signal is selectively modified to represent a color film exposure level;
and
video color corrector means for receiving a plurality of digital video color correction signals, for receiving the corrected film color signal from the film color corrector, and for selectively correcting the received corrected film color signal in accordance with the received digital video color correction signals, wherein the received digital video color correction signals represent a plurality of color video signal characteristics and the amplitude of the received corrected film color signal is selectively modified;
wherein the film color correct means comprises a sensitometric converter for selectively converting the received digital film color signal into the corrected film color signal substantially in accordance with the following formula:
E=E.sub.O [(10.sup.A(D-Dl) -1/(1-10.sup.B(D-Du))].sup.N
where:
E=exposure level of color film dye (represented by the corrected film color signal)
E.sub.O =antilog.sub.10 {0.8/ASA-NX [0.1+log.sub.10 (1-10.sup.-0.1)]}
A=measure of asymmetry of toe ("toe character") of color film dye's characteristic curve =.vertline.Dd-Dl.vertline. [default value:
A=-1].apprxeq.log.sub.10 (1-10.sup.(Dd-Dl))/(Dd-Dl)
Dd=toe density of color film dye
Dl=minimum (base+fog) density of color film dye
D=density of color film dye (represented by the received digital film color signal)
B=measure of asymmetry of shoulder ("shoulder character") of color film dye's characteristic curve =.vertline.Du-Dc.vertline. [default value:
B=1].apprxeq.log.sub.10 (1-10.sup.(dc-Du))/(Dc-Du)
Du=maximum (saturation) density of color film dye
Dc=shoulder density of color film dye N.apprxeq.1/.gamma.
ASA=film speed

15 more elements

film color corrector means for receiving a plurality of digital film color correction signals, for receiving a digital film color signal, and for selectively correcting the received digital film color signal in accordance with the received digital film color correction signals, wherein the received digital film color correction signals represent a plurality of color film characteristics, the received digital film color signal represents a color film dye density, and the received digital film color signal is selectively modified to represent a color film exposure level;
and
video color corrector means for receiving a plurality of digital video color correction signals, for receiving the corrected film color signal from the film color corrector, and for selectively correcting the received corrected film color signal in accordance with the received digital video color correction signals, wherein the received digital video color correction signals represent a plurality of color video signal characteristics and the amplitude of the received corrected film color signal is selectively modified;
wherein the video color corrector means comprises a video standard converter for selectively converting the received corrected film color signal into a video standard color signal, and further wherein the received corrected film color signal is selectively converted into a video standard color signal substantially in accordance with the following formula:
##EQU7## where:
V.sub.C =reference SMPTE 240 M video camera output voltage for colored video signal (represented by the video standard color signal)
L.sub.C =incident colored light producing V.sub.C (represented by the received corrected film color signal)

4 more elements

A digital color corrector for correcting a color signal representing a portion of a colored optical image in accordance with a plurality of color correction parameters, the color corrector comprising:

a color signal port for receiving a digital color signal representing a color film dye density;
a parameter signal port for receiving a plurality of digital color correction signals representing a plurality of color film characteristics;
and
encoder means for selectively encoding the received digital color signal in accordance with the received digital color correction signals, wherein the received digital color correction signals are inserted as separate signal data into the received digital color signals, and wherein the encoded color signal represents a color film exposure level;
wherein the encoder means comprises a sensitometric encoder coupled to selectively generate film color correction data from the received digital color corrections signals and further coupled to selectively insert the generated film color correction data into the received digital color signal, and wherein the film color correction data is generated substantially in accordance with the following formula:
E=E.sub.O [(10.sup.A(D-Dl) -1) /(1-10.sup.B(D-Du))].sup.N
where:
E=exposure level of color film dye (represented by the corrected film color signal)
E.sub.O =antilog.sub.10 {0.8/ASA-Nx [0.1+log.sub.10 (1-10.sup.-0.1) ]}
A=measure of asymmetry of toe ("toe character") of color film dye's characteristic curve =.vertline.Dd-Dl.vertline. [default value:
A=-1].apprxeq.log.sub.10 (1-10.sup.(Dd-Dl))/(Dd-Dl)
Dd=toe density of color film dye
Dl=minimum (base+fog) density of color film dye
D=density of color film dye (represented by the received digital film color signal)
B=measure of symmetry of shoulder ("shoulder character") of color film dye's characteristic curve =.vertline.Du-Dc.vertline. [default value:
B=1].apprxeq.log.sub.10 (1-10.sup.(Dc-Du))/(Dc-Du)
Du=maximum (saturating) density of color film dye
Dc=shoulder density of color film dye N.apprxeq.1/.gamma.
ASA=film speed

16 more elements

A method for transforming a film color signal representing a portion of a colored optical film image into a video color signal in accordance with film and video color correction parameters associated with color film and video signal characteristics, respectively, the transformation method comprising the steps of:

receiving a plurality of digital film color correction signals representing a plurality of color film characteristics;
receiving a digital film color signal representing a color film dye density;
selectively correcting the received digital film color signal in accordance with the received digital film color corrections signals, wherein the received digital film color signal is selectively modified to represent a color film exposure level, by selectively converting the received digital film color signal into the corrected film color signal substantially in accordance with the following formula:
E=E.sub.O [(10.sup.A(D-Dl) -1) /(1-10.sup.B(D-Du))].sup.N
where:
E=exposure level of color film dye (represented by the corrected film color signal)
E.sub.O =antilog.sub.10 {0.8/ASA-Nx [0.1+log.sub.10 (1-10.sup.-0.1)[}
A=measure of asymmetry of toe ("toe character") of color film dye's characteristic curve =.vertline.Dd-Dl.vertline. [default value:
A=-1].apprxeq.log.sub.10 (1-10.sup.(Dd-Dl))/(Dd-Dl)
Dd=toe density of color film dye
Dl=minimum (base+fog) density of color film dye
D=density of color film dye (represented by the received digital film color signal)
B=measure of asymmetry of shoulder ("shoulder character") of color film dye's characteristic curve =.vertline.Du-Dc.vertline. [default value:
B=1].apprxeq.log.sub.10 (1-10 .sup.(Dc-Du))/(Dc-Du)
Du=maximum (saturation) density of color film dye
Dc=shoulder density of color film dye N.apprxeq.1/.gamma.
ASA=film speed;
receiving a plurality of digital video color correction signals representing a plurality of video signal characteristics;
receiving the corrected film color signal;
and
selectively correcting the received corrected film color signal in accordance with the received digital video color correction signals, wherein the amplitude of the received corrected film color signal is selectively modified.

18 more elements

Dependencies are inferred from the claim text.

Digital color correction system and method

Life of this patent

Digital color correction system and method

Life of this patent

Abstract

Claims43