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US 5,212,518 AGranted
Tonal conversion method for a faded color photographic original picture
AssigneeYamatoya & Co., Ltd.
InventorsTakashi Numakura, Iwao Numakura
Life of this patent
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Abstract
Herein disclosed is a tonal conversion method for a faded color original picture useful upon producing a printed picture in a halftone from a faded color photographic original in a continuous tone. As picture information of tonal conversion, unfaded light intensity values (Xn) of a pixel in a faded color photographic original, instead of density information values (D.sub.Fn) of a corresponding pixel of the same, are used. The light intensity values (Xn) may be rationally determined, utilizing an assumption of dye loss and density characteristic curves (S-DCC) of a photographic photosensitive material. The light intensity values (Xn) are then converted into halftone dot area % values by conduction of a specific tonal conversion formula.
Claims8
A tonal conversion method used upon producing a printed picture in a halftone from a faded color photographic original in a continuous tone comprising the steps of:
- (i) obtaining a density information value (D.sub.Fn) of a pixel (n point) of a color (R, G or B) of the original picture from the faded color photographic original;
- (ii) determining an unfaded density information value (D.sub.Sn) of the pixel of the color from the density information value (D.sub.Fn) by means of Formula (1):
- D.sub.Sn =D.sub.Fn .multidot.(D.sub.Su /D.sub.Fu) (1)
- where
- D.sub.Su :
- a density information value of an unexposed area (the darkest area) of an unfaded photographic photosensitive material, taking a preset value;
- and
- D.sub.Fu :
- a measured density information value of an unexposed area (the darkest area) of the faded color photographic original;
- (iii) determining a light intensity value (Xn) for the color from the density information value (D.sub.Sn) by utilizing photographic density characteristic functions for the color (R, G or B) of an unfaded photographic photosensitive material used upon photographing the color photographic original and determining a basic light intensity value (.sub.xn);
- and
- (iv) converting the basic light intensity value (.sub.xn) for the color into a halftone dot area % value (a.sub.Xn) for a corresponding color plate (C, M or Y plate) by means of Tonal Conversion Formula (2-1):
- A.sub.Xn =a.sub.H +.alpha.(1-10.sup.-.kappa..multidot.Xn)(a.sub.S -a.sub.H)/(.alpha.-.beta.) (2-1)
- where
- .sub.Xn :
- a basic light intensity value given by .sub.Xn =[Xn-X.sub.Hn ], said .sub.Xn being determined from a difference between a light intensity value (Xn) determined from an unfaded density information value (D.sub.Sn) corresponding to a density information value (D.sub.Fn) of a pixel (n point) on an original picture and a light intensity value (X.sub.Hn) determined from an unfaded density information value (D.sub.SH) corresponding to a density information value (D.sub.FH) of a highlight area (H area) on the original picture, by utilizing photographic density characteristic functions;
- a.sub.Xn :
- a halftone dot area % value set to a pixel (n point) on a color plate (C, M or Y) corresponding to a given pixel (n point) in an original;
- a.sub.H :
- a halftone dot area % value preset to H part of a color plate;
- a.sub.S :
- a halftone dot area % value preset to S part of a color plate;
- .alpha.:
- a surface reflectance of a paper used for forming a printed picture;
- .beta.:
- a value determined by .beta.=10.sup.-.gamma. ;
- .kappa.:
- a value determined by .kappa.=.gamma./(X.sub.Sn -X.sub.Hn),
- where X.sub.Sn is alight intensity value determined from
- an unfaded density information value (D.sub.SS) corresponding to a density information value (D.sub.FS) of a shadow area (S area) on an original picture, by utilizing an unfaded photographic density characteristic functions;
- and
- .gamma.:
- an arbitrary coefficient.
30 more elements
A tonal conversion method used upon producing a printed picture in a halftone from a faded color photographic original in a continuous tone comprising the steps of:
- (i) obtaining a density information value (D.sub.Fn) of a pixel (n point) for a color (R, G or B) of the original picture from the faded color photographic original;
- (ii) determining photographic density characteristic functions of a faded photographic photosensitive material from corresponding photographic density characteristic functions for the color (R, G or B) of an unfaded photographic photosensitive material used upon photographing the color photographic original by means of formula (3):
- F.sub.F (Xn)=F.sub.S (Xn).multidot.(D.sub.Fu /D.sub.Su) (3)
- where
- F.sub.F (Xn):
- showing a part of independent variables of a photographic density characteristic function D.sub.F =F.sub.F (Xn) of a faded photographic photosensitive material;
- F.sub.S (Xn):
- showing a part of independent variables of a photographic density characteristic function D.sub.S =F.sub.S (Xn) of a known unfaded photographic photosensitive material;
- D.sub.Su :
- a density information value of an unexposed area (the darkest area) of an unfaded photographic photosensitive material, taking a preset value;
- D.sub.Fu :
- a measured density information value of an unexposed area (the darkest area) of the faded color photographic original;
- (iii) determining a light intensity value (Xn) from the density information value (D.sub.Fn) of the color by utilizing the photographic density characteristic functions for the color of the faded photographic photosensitive material and further determining a basic light intensity value (.sub.xn);
- and
- (iv) converting the basic light intensity value (.sub.Xn) of the color into a halftone dot area % value (a.sub.Xn) for a corresponding color plate (C, M or Y plate) by means of tonal conversion formula (2--2):
- a.sub.Xn =a.sub.H +.alpha.(1-10.sup.-.kappa..multidot.xn)(a.sub.S -a.sub.H)/(.alpha.-.beta.) (2--2)
- where
- .sub.xn :
- a basic light intensity value given by .sub.xn =[Xn-X.sub.Hn ], said .sub.xn being determined from a difference between a light intensity value (Xn) determined from a corresponding density information value (D.sub.Fn) of a pixel (n point) on an original picture and a light intensity value (X.sub.Hn) determined from a corresponding density information value (D.sub.FH) in a highlight area (H area) on the original picture, by utilizing faded photographic density characteristic functions;
- a.sub.Xn :
- a halftone dot area % value set to a pixel (n point) on a color plate (C, M or Y) corresponding to a given pixel (n point) in an original);
- a.sub.H :
- a halftone dot area % value present to H part of a color plate;
- a.sub.S :
- a halftone dot area % value preset to S part of a color plate;
- .alpha.:
- a surface reflectance of a paper used for forming a printed picture;
- .beta.:
- a value determined by .beta.=10.sup.-.gamma. ;
- .gamma.:
- an arbitrary coefficient;
- and
- .kappa.:
- a value determined by .kappa.=.gamma./(X.sub.Sn -X.sub.Hn), where X.sub.Sn shows a light intensity value determined from a density information value (D.sub.FS) in a shadow area (S area) on an original, by utilizing faded photographic density characteristic functions.
31 more elements
Dependencies are inferred from the claim text.