Tonal conversion method for pictures

Claim 1

A method for producing a reproduced picture by tonal conversion of an original picture on the basis of pictorial information from the original picture, which comprises: (i) setting the density value (H n ) of the highlight area of the original picture, the density value (S n ) of the shadow area of the original picture and an individual density characteristic curve fD n (x) ranging from said H n to said S n , where x indicates a physical value correlated to the densities (D) of the original picture and reproduced picture, such as exposure; (ii) setting the density value (H o ) of the highlight area and the density value (S o ) of the shadow area of a standard original picture, which can provide a reproduced picture having suitable picture quality for the visual feeling of men, as well as a standard density characteristic curve fD o (x) ranging from said H o to said S o ; (iii) adjusting the individual density characteristic curve fD n (x) to the standard density characteristic curve fD o (x) and further determining an adjusted density information value D.sub.φ on the standard original picture corresponding to the density information value D n of a desired picture element on the original picture; and (iv) then conducting tonal conversion of the picture in said density range on the basis of the thus-obtained adjusted density information value D o on the standard original picture corresponding to the density information value D n of the desired picture element on the original picture by using the following tonal conversion formula: ##EQU7## where (D o -H o ): the base density information datum obtained by subtracting the density value H.sub.φ of the highlight area of the standard original picture from the adjusted density information value D o on the standard original picture corresponding to the density information value D n of the desired picture element on the original picture; y: the halftone density intensity on the reproduced picture, corresponding to the desired picture element on the original picture; y H : a desired halftone density intensity set for the highlight area on the picture to be reproduced; y S : a desired halftone density intensity set for the shadow area on the picture to be reproduced; α: the surface reflectance of a base material on which the reproduced picture is to be shown; β: a value obtained from β=10 - γ ; κ: another value determined from γ/(S o -H o ); and γ: a desired optional factor.

Claim 2

A method for producing a reproduced picture by tonal conversion of an original picture on the basis of pictorial information from the original picture, which comprises: (i) setting the density value (H n ) of the highlight area of the original picture, the density value (S n ) of the shadow area of the original picture and an individual density characteristic curve fD n (x) ranging from said H n to said S n , where x indicates a physical value correlated to the densities (D) of the original picture and reproduced picture, such as exposure; (ii) setting the density value (H o ) of the highlight area and the density value (S o ) of the shadow area of a standard original picture, which can provide a reproduced picture having suitable picture quality for the visual feeling of men, as well as a standard density characteristic curve fD o (x) ranging from said H o to said S o ; (iii) adjusting the individual density characteristic curve fD n (x) to the standard density characteristic curve fD o (x) and further determining an adjusted density information value D.sub.φ on the standard original picture corresponding to the density information value D n of a desired picture element on the original picture; and (iv) then conducting tonal conversion of the picture in said density range on the basis of the thus-obtained adjusted density information value D o on the standard original picture corresponding to the density information value D n of the desired picture element on the original picture by using the following tonal conversion formula: ##EQU7## where (D o -H o ): the base density information datum obtained by subtracting the density value H.sub.φ of the highlight area of the standard original picture from the adjusted density information value D o on the standard original picture corresponding to the density information value D n of the desired picture element on the original picture; y: the halftone density intensity on the reproduced picture, corresponding to the desired picture element on the original picture; y H : a desired halftone density intensity set for the highlight area on the picture to be reproduced; y S : a desired halftone density intensity set for the shadow area on the picture to be reproduced; α: the surface reflectance of a base material on which the reproduced picture is to be shown; β: a value obtained from β=10 - γ ; κ: another value determined from γ/(S o -H o ); and γ: a desired optional factor.