Photographic prints and methods for printing photographic prints.

Abstract

To provide a printed matter whose image quality and the like are similar to those of silver halide photography.SOLUTION: A photographic printed matter 1 is obtained by laminating at least a base material 10 and a monochrome image layer 11 formed by offset printing using double tone printmaking. The monochrome image layer 11 includes a gray image layer 111 formed using gray ink whose black pigment concentration is low, and a black image layer 110 formed using a black ink whose black pigment concentration is enhanced. In order that image quality may be similar to that of silver halide photography, a tone producibility of a bright part is high in the gray image layer 111, and tone producibility of a bright part is low and reproducibility of half tone is high in the black image layer 110 in the photographic printed matter 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004]

[0001] The present invention belongs to the technical field of printed photographs printed by offset printing.

Background Art

[0002] The methods of forming photographs of landscapes or people on a recording medium are roughly divided into two types: the silver salt method and the printing method. With the digitalization of photographs accompanying the spread of digital cameras, in the printing method, inkjet printing that ejects fine droplets of ink onto a recording medium has become the mainstream.

[0003] The quality of conventional photographs by the silver salt method (hereinafter, silver salt photographs) is superior to that of photographs by the printing method (hereinafter, printed photographs) in various aspects. Therefore, when properties similar to those of silver salt photographs are required for printed photographs, it is necessary to devise ways to bring the quality of printed photographs closer to that of silver salt photographs.

[0004] One of the qualities in which silver salt photographs are superior to printed photographs is glossiness. In the silver salt method, the inside of the photographic paper that serves as the recording medium of the silver salt photograph develops color to form an image. Since a transparent protective layer (for example, a gelatin layer) is provided on the surface of the photographic paper, the glossiness of the silver salt photograph is high. By providing a transparent protective layer on the surface, the durability such as water resistance of the silver salt photograph is also improved.

[0005] In the printing method, an image is formed by placing ink on a recording medium such as paper. Therefore, a difference occurs between the surface of the recording medium and the glossiness of the ink, and in printed photographs, a uniform glossiness that does not depend on the light and shade of the image, as in silver salt photographs, cannot be obtained. Also, in terms of water resistance and durability, printed photographs are inferior to silver salt photographs.

[0006] As a measure to bring the quality of printed photographs closer to that of silver salt photographs, a technique of applying UV varnish (UV: Ultra Violet) on printed photographs has been disclosed in various documents such as Patent Document 1. By applying UV varnish on printed photographs, the durability such as glossiness and water resistance of printed photographs is improved.

Prior Art Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-330570 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, the inferiority of printed photographs compared to silver halide photographs is not limited to glossiness. Printed photographs are also inferior to silver halide photographs in terms of image quality (reproducibility). Therefore, the present invention provides a printed material and a method for printing such a printed material that brings image quality and other properties closer to that of silver halide photographs. [Means for solving the problem]

[0009] The first invention, which solves the above-mentioned problems, comprises a substrate and at least a monochrome image layer formed by offset printing using a duotone platemaking method, wherein the monochrome image layer includes a gray image layer formed using gray ink with a low concentration of black pigment and a black image layer formed using black ink with a high concentration of black pigment. The gray tone curve used for plate making of gray plates and the black tone curve used for plate making of black plates are each made into a curve that arcs from a starting point where the density gradation value is the minimum and the percentage of halftone dots is the minimum, to an ending point where the density gradation value is the maximum and the percentage of halftone dots is the maximum, and in the gray tone curve, the slope in the bright areas is made greater than the slope in the bright areas from the midtones to the dark areas compared to a reference line connecting the starting point and the ending point by a straight line, and in the black tone curve, the slope in the bright areas is made smaller than the reference line, and the slope in the midtones to the dark areas is made greater than the reference line, The aforementioned grayscale image layer reproduces tones from bright areas to midtones with 8-bit equivalent gradation to enhance the reproduction of tones in bright areas, while the aforementioned blackscale image layer reproduces tones from midtones to dark areas with 8-bit equivalent gradation to reduce the reproduction of tones in bright areas and enhance the reproduction of tones in midtones. In the first invention, it is preferable that the black ink is an ink using carbon black as the black pigment, and the gray ink is a lightfast ink using carbon black as the black pigment. Furthermore, in the first invention, it is preferable to laminate a varnish layer using a glossy varnish onto the surface. UV varnish is preferred as the varnish. Furthermore, in the first invention, it is preferable to use a paper with a similar texture to photographic paper used in silver halide photography as the base material.

[0010] The second invention, which solves the above-mentioned problems, includes a monochrome image layer formation step in which a monochrome image layer is laminated on a substrate by offset printing using duotone plate making, and the monochrome image layer formation step is The image is made to form a curve that arcs from a starting point where the density gradation value is at its minimum and the percentage of halftone dots is at its minimum, to an ending point where the density gradation value is at its maximum and the percentage of halftone dots is at its maximum, and the slope of the bright areas is made smaller than that of a reference line connecting the starting point and the ending point by a straight line, and the slope from the midtones to the dark areas is made larger than that of the reference line, Reproduces the midtones to dark areas with 8-bit equivalent gradation. hand , a process of forming a black image layer, in which a black plate is made in which the tonal reproducibility of the highlights is reduced and the tonal reproducibility of the midtones is increased, and a black image layer is formed using the black plate and black ink with increased black pigment concentration, By creating a curved shape that arcs from the aforementioned starting point to the aforementioned ending point, making the slope of the bright areas greater than the aforementioned reference line, and making the slope from the midtones to the dark areas smaller than the slope of the bright areas, It reproduces the range from highlights to midtones with 8-bit equivalent gradation. hand The method for printing photographic prints is characterized by including a gray image layer formation step, which involves preparing a gray plate with improved tonal reproduction of highlights, and forming a gray image layer using the gray plate and a gray ink with a low concentration of black pigment. In the second invention, it is preferable that the black ink is an ink using carbon black as the black pigment, and the gray ink is a lightfast ink using carbon black as the black pigment. Furthermore, the second invention preferably includes a varnish layer formation step in which a varnish layer using a glossy varnish is laminated onto the surface. UV varnish is preferably used as the varnish. Furthermore, in the second invention, it is preferable to use paper with a similar texture to photographic paper used in silver halide photography as the base material. [Effects of the Invention]

[0011] In this invention, in order to bring the image quality and other characteristics closer to those of silver halide photography, the monochrome image layer formed by offset printing using duotone plate making has high tonal reproduction in the highlights in the gray image layer, while the black image layer has low tonal reproduction in the highlights and high tonal reproduction in the midtones. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram illustrating a photographic print according to this embodiment. [Figure 2] A diagram illustrating the challenges of conventional printed photography. [Figure 3] A diagram illustrating the tone curve according to this embodiment. [Figure 4] A diagram for explaining a printing method of a photographic print. [Figure 5] A diagram showing an original image. [Figure 6] A diagram for explaining a sumi image layer. [Figure 7] A diagram for explaining a gray image layer. [Figure 8] A diagram for explaining a gray scale matrix. [Figure 9] A diagram for explaining a first test chart. [Figure 10] A diagram illustrating the chromaticity variation of an inkjet print. [Figure 11] Figure 1 illustrating the chromaticity variation of a photographic print according to the present invention. [Figure 12] Figure 2 illustrating the chromaticity variation of a photographic print according to the present invention. [Figure 13] A diagram illustrating the density transition in an inkjet print. [Figure 14] Figure 1 illustrating the density transition in a photographic print according to the invention. [Figure 15] Figure 2 illustrating the density transition in a photographic print according to the present invention. [Figure 16] A diagram for explaining a second test chart. [Figure 17] A diagram illustrating the glossiness variation in an inkjet print. [Figure 18] Figure 1 illustrating the glossiness variation of a photographic print according to the present invention. [Figure 19] Figure 2 illustrating the glossiness variation of a photographic print according to the present invention. [Figure 20] Figure 1 illustrating the chromaticity variation in a monochrome print. [Figure 21] Figure 1 illustrating the density transition in a monochrome print. [Figure 22] Figure 2 illustrating the chromaticity variation in a monochrome print. [Figure 23] Figure 2 illustrating the density transition in a monochrome print.

Mode for Carrying Out the Invention

[0013] Embodiments of the present invention will now be described. These embodiments are provided to facilitate understanding of the present invention, and the present invention is not limited to these embodiments. Unless otherwise specified, the drawings are schematic diagrams drawn to facilitate understanding of the present invention.

[0014] This document describes the photographic print and the method for printing the photographic print according to the present invention. The photographic print 1 according to the present invention is a printed material devised to bring the quality of a printed photograph closer to that of a silver halide photograph. Furthermore, the method for printing the photographic print according to the present invention is a method for printing a printed material that is close to the quality of a silver halide photograph.

[0015] First, the photographic print 1 according to this embodiment will be described. Figure 1 is a diagram illustrating the photographic print 1 according to this embodiment. According to Figure 1, the photographic print 1 is constructed by laminating, in order from the surface, a varnish layer 12 formed by a varnish coat, a monochrome image layer 11 formed by offset printing using duotone plate making, and a base material 10 which is the printing paper for the photographic print 1.

[0016] The duotone platemaking used for forming the monochrome image layer 11 is a printing method that uses two or more plates to form the monochrome image layer 11. In this embodiment, the monochrome image layer 11 is formed using a black plate with black ink and a gray plate with gray ink. Therefore, in Figure 1, the monochrome image layer 11 includes a black image layer 110 formed using black ink and a gray image layer 111 formed using gray ink. In this embodiment, black ink is an ink with a high concentration of black pigment. Also in this embodiment, gray ink is an ink with a lower concentration of black pigment than black ink.

[0017] In this embodiment, the photographic print 1 includes only a monochrome image layer 11. Therefore, the photographic print 1 according to this embodiment is a monochrome photograph. In addition to the monochrome image layer 11, the photographic print 1 may include a color image layer. The color image layer is a layer printed using inks such as cyan ink, magenta ink, and yellow ink.

[0018] Figure 2 illustrates the challenges in conventional printed photographs. The table in Figure 2 lists the quality items related to photographs as texture, image quality, and durability. In the table in Figure 2, the challenges related to texture are "making gloss uniform," "matching the paper texture to silver halide photographs," and "creating a sense of unity between the paper and the image." In the table in Figure 2, the challenges related to image quality are "making hue uniform," "improving sharpness," and "improving tonal reproduction." Furthermore, in the table in Figure 2, the challenges related to durability are "improving lightfastness," "improving water resistance," and "improving stain resistance."

[0019] In this embodiment, in order to solve the problems related to texture and some of the problems related to durability, the photographic print 1 uses a base material 10 that has a similar texture to photographic paper used in silver halide photography, and furthermore, a varnish layer 12 is laminated on the surface of the photographic print 1.

[0020] In the photographic print 1 according to this embodiment, in order to solve the problem related to texture, "matching the texture of the paper to that of silver halide photography," a paper with a texture similar to that of photographic paper used in silver halide photography is used as the base material 10. Two types of photographic paper are mainly used for silver halide photography: RC photographic paper (RC: Resin Coated) and baryta photographic paper. Therefore, it is preferable to use either a paper with a texture similar to RC photographic paper or a paper with a texture similar to baryta photographic paper for the base material 10 laminated in the photographic print 1 according to this embodiment. As a paper with a texture similar to RC photographic paper, cast coated paper (for example, Esprit Coat) can be used, and a weight of 180 kg in a 4 / 6 size is suitable. As a paper with a texture similar to baryta photographic paper, high-quality printing paper that retains the texture of the paper (for example, Van Nuvo V White) can be used, and a weight of 235 kg in a 4 / 6 size is suitable. Whether to use paper with a texture similar to RC photographic paper or paper with a texture similar to baryta photographic paper should be decided based on the desired finished appearance.

[0021] In the photographic print 1 according to this embodiment, in order to solve the problem of "enhancing gloss" which is related to texture, UV varnish (UV: Ultraviolet), which has a higher gloss than OP varnish (OP: Overprint), which is commonly used in offset printing, is used for the varnish layer 12. For example, if the varnish layer 12 is formed to closely resemble the gloss of silver halide photographs, the monochrome image layer 11 will appear to be contained within the varnish layer 12, thereby increasing the sense of unity between the substrate 10 and the monochrome image layer 11. Furthermore, by laminating the varnish layer 12 on the surface of the photographic print 1, the water resistance and stain resistance, which are issues related to durability, are also improved.

[0022] To address the durability challenge of "improving lightfastness," carbon black is used as the black pigment in the photographic print 1 according to this embodiment. In this embodiment, the black ink is an ink with a high concentration of carbon black. The gray ink is a lightfast ink with a low concentration of carbon black. Note that a lightfast ink is an ink in which components that improve resistance to ultraviolet light are added to the components of a normal ink.

[0023] Because carbon black has high lightfastness, the lightfastness of the black image layer 110 formed using a black ink with a high concentration of carbon black is high. Also, although the concentration of carbon black in gray ink is low, using a lightfast ink in the gray ink increases the lightfastness of the gray image layer 111 formed using the gray ink.

[0024] In conventional printed photographs, the issue of "improving sharpness," which relates to image quality, arises from the penetration of liquid ink into the recording medium and the low resolution of the print. Therefore, in this invention, a printing plate output by CTP (Computer To Plate), which can express even fine halftone dots, is used, and high-definition offset printing is performed with a screen ruling of 200 lines or more as a guideline. By forming a monochrome image layer 11 with high-definition offset printing, the issue of "improving sharpness," which relates to image quality, can be improved.

[0025] In conventional printed photographs, the challenge of "uniform hue" in terms of image quality arises because shades are expressed by layering multiple color inks (cyan, magenta, and yellow inks, and other spot color inks). Depending on the color balance of the inks, the hue can change unnaturally. In contrast, in this embodiment, only achromatic inks are used to express shades, so the hue does not change unnaturally.

[0026] In this embodiment, in photographic print 1, in order to solve the problems related to image quality, a monochrome image layer 11 is formed by offset printing using duotone platemaking with at least two plates: a black plate using black ink and a gray plate using gray ink. In this embodiment, efforts have been made to achieve image quality equivalent to silver halide photography by focusing on the tone curve used in platemaking.

[0027] When printing using black ink in the highlight areas, small, dense halftone dots are sparsely distributed on the surface of the recording medium, resulting in a rough texture. Therefore, in this embodiment of offset printing using duotone platemaking, the gray ink and black ink are assigned to different ranges of tonal reproduction. In the case of gray ink, the tonal reproduction accuracy of the highlight areas is increased to enable the reproduction of gradations from highlights to midtones. In the case of black ink, the tonal reproduction accuracy of the highlight areas is decreased, while the tonal reproduction accuracy of the midtones is increased to enable the reproduction of gradations from midtones to dark areas.

[0028] The number of tonal gradations that can be reproduced with a typical CTP printing plate used in offset printing is 8 bits. However, in the photographic print 1 according to this embodiment, the above-described ingenuity allows for the reproduction of tonal gradations from bright areas to midtones with 8 bits equivalent using gray ink, and further, the reproduction of tonal gradations from midtones to dark areas with 8 bits equivalent using black ink. Therefore, the photographic print 1 according to this embodiment can reproduce tonal gradations beyond 8 bits.

[0029] From here, we will explain the third method of printing photographic prints. First, we will explain the details of duotone plate making. In the duotone plate making of this embodiment, since a black plate using black ink and a gray plate using gray ink are made, a tone curve used for making the black plate and a tone curve used for making the gray plate are required. In this embodiment, the tone curve used for making the black plate is called the black plate tone curve 20, and the tone curve used for making the gray plate is called the gray plate tone curve 21.

[0030] Figure 3 illustrates the tone curve according to this embodiment. A tone curve is a graph that maps the tonal values ​​of the original document density to the corresponding percentage of halftone dots. In Figure 3, the horizontal axis represents the tonal values ​​of the original document density, and the vertical axis represents the percentage of halftone dots.

[0031] In Figure 3, the gray tone curve 21 and the black tone curve 20 are shown as solid lines. The gray tone curve 21 is a thinner solid line than the black tone curve 20. Also, in Figure 3, the baseline 22 is shown as a dotted line. The baseline 22 is the initial tone curve without any correction, and the baseline 22 is a straight line sloping upwards to the right with a 45-degree angle.

[0032] In Figure 3, the gray tone curve 21 and the black tone curve 20 are curved. This is because if the tone curves used in double-tone plate making were straight lines or polylines, the changes in halftone dots would become coarse at the ends of the straight lines or at the points where the curves bend, resulting in a loss of tonal continuity. Therefore, in this embodiment, as shown in Figure 3, the gray tone curve 21 and the black tone curve 20 are made into curves that form arcs without moving the starting point (minimum density gradation value, minimum halftone dot percentage) and the ending point (maximum density gradation value, maximum halftone dot percentage), thereby making the changes in gradation gradation gradual and preventing a loss of tonal continuity.

[0033] In the photographic print 1 according to this embodiment, the gray tone curve 21 and the black tone curve 20 are used to make it easier to bring out tones from highlights to midtones compared to the baseline 22. In order to make it easier to bring out tones compared to the baseline 22, it is necessary to increase the slope of the tone curve to be greater than the slope of the baseline 22 and increase the contrast.

[0034] In this embodiment, the gray version is a version that enhances the reproduction of tonal details in the highlight areas. For this reason, in Figure 3, the slope of the gray version tone curve 21 in the highlight areas is large. Specifically, in Figure 3, the slope of the gray version tone curve 21 in the highlight areas is approximately 60 degrees, which is larger than the slope of the baseline 22.

[0035] Increasing the slope of the gray tone curve 21 in the highlight areas increases the percentage of halftone dots in the highlight areas compared to the baseline 22. However, because gray ink is lighter in color than black ink, even increasing the percentage (area) of halftone dots in the highlight areas does not make the gray ink dots stand out. The color density when printing 100 percent halftone dots using gray ink is about the same as a midtone when using black ink.

[0036] The black ink version is designed to reduce the tonal reproduction accuracy in the highlight areas and increase the tonal reproduction accuracy from the midtones to the shadows. Therefore, in Figure 3, the slope of the black ink tone curve 20 in the highlight areas is small. In Figure 3, the slope of the black ink tone curve 20 in the highlight areas is approximately 20 degrees, which is smaller than the slope of the baseline 22.

[0037] As a result of increasing the slope in the highlight areas, the slope of the grayscale tone curve 21 becomes smaller than the slope in the highlight areas from the midtones to the dark areas. In Figure 3, the slope of the grayscale tone curve 21 in the midtones is almost the same as the slope of the baseline 22. In Figure 3, the slope of the grayscale tone curve 21 in the dark areas is smaller than the slope of the baseline tone curve.

[0038] Therefore, the grayscale version cannot enhance the tonal gradation of the midtones. In this embodiment, the slope of the black version tone curve 20 in the midtones is increased to make it easier to bring out the midtones using the black version. In the figure, the slope of the black version tone curve 20 from the midtones to the dark areas is approximately 60 degrees. This is greater than the slope of the baseline 22, which is 45 degrees.

[0039] As explained above, in Figure 3, the slope of the highlights is steep in the gray tone curve 21. Furthermore, in the black tone curve 20, the slope of the highlights is small, and the slope of the midtones is steep. Therefore, in the photographic print 1 according to this embodiment, the gray tone can reproduce the range from highlights to midtones with 8-bit equivalent gradation, and the black tone can reproduce the range from midtones to shadows with 8-bit equivalent gradation. For this reason, even if the gradation that can be reproduced with a single plate used in offset printing is 8 bits, the photographic print 1 according to this embodiment can reproduce gradation beyond 8 bits. Note that, since the photographic print 1 according to this embodiment can reproduce gradation beyond 8 bits, it is desirable to use 16-bit gradation for the original density on the horizontal axis of the tone curve, rather than 8-bit gradation.

[0040] From here, we will explain the third method of printing photographic materials. Figure 4 is a diagram illustrating the third method of printing photographic materials.

[0041] As shown in Figure 4, the photoprinting method 3 according to this embodiment includes a monochrome image layer forming step 30 in which a monochrome image layer 11 is formed on a substrate 10 by offset printing. Furthermore, the photoprinting method 3 according to this embodiment includes a varnish layer forming step 31 in which a varnish layer 12 is laminated on the substrate 10 on which the monochrome image layer 11 is laminated, as a step to be performed after the monochrome image layer forming step 30.

[0042] The monochrome image layer formation step 30 according to this embodiment is a step in which a monochrome image layer 11 is formed by offset printing using duotone plate making. The monochrome image layer formation step 30 includes a black image layer formation step 300 for forming a black image layer 110 and a gray image layer formation step 301 for forming a gray image layer 111. A color layer formation step for forming a color layer can be included between the monochrome image layer formation step 30 and the varnish layer formation step 31.

[0043] In order to obtain a texture similar to that of silver halide photographs, it is desirable to use a paper for the base material 10 that has a similar texture to the photographic paper used in silver halide photographs in the printing method 3 for photographic prints. Specifically, it is desirable to use a paper for the base material 10 that resembles either RC photographic paper or baryta photographic paper.

[0044] The plate used in the black image layer formation process 300 is a black plate made using a black plate tone curve 20 in which the slope of the highlights is reduced and the slope of the midtones is increased. The ink used in the black image layer formation process 300 is an ink with a high concentration of black pigment. To improve the lightfastness of the black image layer 110, it is preferable to use carbon black as the black pigment.

[0045] Furthermore, the plate used in the gray image layer formation process 301 is a gray plate made using a gray plate tone curve 21 with a large gradient in the bright areas. The ink used in the gray image layer formation process 301 is an ink with a low density of black areas. In order to enhance the glossiness of the gray image layer 111, it is preferable to use a lightfast ink with carbon black as the black pigment for the gray ink.

[0046] In the varnish layer formation process 31, it is desirable to use UV varnish to enhance the gloss of the photographic print 1. Furthermore, in order to obtain a texture similar to that of a silver halide photograph, the amount of varnish applied in the varnish layer formation process 31 should be adjusted so that the gloss of the photographic print 1 is close to that of a silver halide photograph.

[0047] Finally, we will explain examples of the black image layer 110 and the gray image layer 111. Figure 5 shows the original image 4, Figure 6 illustrates the black image layer 110, and Figure 7 illustrates the gray image layer 111. Note that the photographic print 1 based on the original image 4 shown in Figure 5 is a print made by overprinting the black image layer 110 shown in Figure 6 and the gray image layer 111 shown in Figure 7 onto the substrate 10.

[0048] As shown in Figure 3, the black tone curve 20 used to form the black image layer 110 has a reduced slope in the bright areas. Therefore, in the black image layer 110 shown in Figure 6, no image of black ink appears in the area corresponding to the bright areas of the original image 4. As shown in Figure 3, the black tone curve 20 used to form the black image layer 110 has a increased slope in the midtones. Therefore, in the black image layer 110 shown in Figure 6, an image of black ink appears in the area corresponding to the midtones to dark areas of the original image 4.

[0049] In contrast, as shown in Figure 3, the gray tone curve 21 used as the plate for forming the gray image layer 111 has a steeper slope in the bright areas. As a result, in the gray image layer 111 shown in Figure 7, an image made of gray ink appears in the region corresponding to the transition from the bright areas to the dark areas of the original image 4.

[0050] Next, we will explain the results of evaluating the quality of the photographic print 1 according to the present invention. In order to clarify the advantages of the present invention, this disclosure compares the quality of the photographic print 1 according to the present invention with the quality of a printed material printed using an inkjet method (hereinafter referred to as "inkjet printed material").

[0051] The quality of the photographic print 1 according to the present invention is evaluated by assessing the chromaticity change accompanying the transition in tonal values. Furthermore, the quality of the photographic print 1 according to the present invention is evaluated by assessing the density change accompanying the transition in tonal values. Silver halide photographs form images using blackened silver. Therefore, silver halide photographs have the characteristic that the color does not change even when the tonal value changes. Also, due to the exposure characteristics of the sensitizing material, the density change accompanying the transition in tonal values ​​is smooth in silver halide photographs. If the chromaticity change accompanying the transition in tonal values ​​is drastic, the appearance of the photograph becomes unnatural. Therefore, a smaller chromaticity change accompanying the transition in tonal values ​​indicates higher photographic quality. Also, if the density change accompanying the transition in tonal values ​​is not smooth, the appearance of the photograph becomes unnatural. Therefore, a smoother density change accompanying the transition in tonal values ​​indicates higher photographic quality.

[0052] Furthermore, the quality of the photographic print 1 according to the present invention is also evaluated in terms of the change in glossiness with respect to the transition in tonal values. In silver halide photography, the image is formed inside the photographic paper, so there is almost no change in glossiness with respect to the transition in tonal values. However, if the change in glossiness with respect to the transition in tonal values ​​is large, the appearance of the photograph becomes unnatural. This is especially noticeable when light is reflected off it. Therefore, a smaller change in glossiness with respect to the transition in tonal values ​​indicates higher photographic quality.

[0053] First, we will compare the chromaticity changes and density changes associated with the transition of gradation values ​​between the photographic print 1 and an inkjet print according to the present invention. Figure 8 is a diagram illustrating the grayscale 50 created to evaluate the chromaticity changes and density changes. Figure 9 is a diagram illustrating the first test chart 5 used when evaluating the chromaticity changes and density changes.

[0054] The grayscale 50 shown in Figure 8 is represented by the three primary colors of light: red (R), green (G), and blue (B). By using equal amounts of each, it can create any shade of gray. This is because grayscale 50 is handled as image data. The number of RGB values ​​in grayscale 50 shown in Figure 8 is 511. Therefore, the number of gradations for grayscale 50 is approximately 9 bits, and it is handled as 16-bit image data.

[0055] In the grayscale 50 illustrated in Figure 8, one color swatch 500 corresponds to one tone. Therefore, the number of color swatches 500 included in the grayscale 50 is 511. Each column of the grayscale 50 contains 16 color swatches 500. The grayscale 50 is arranged in 32 columns, each containing 16 color swatches 500.

[0056] Each grayscale value corresponds to one density. Forward order means that the density changes from light to dark. The grayscale 50 shown in Figure 8 is in forward order. In a forward-ordered grayscale 50, the density increases in the column direction. In the column direction of a forward-ordered grayscale 50, the density increases from top to bottom. Also, in a forward-ordered grayscale 50, the density increases in the row direction. In the row direction of a forward-ordered grayscale 50, the density increases from left to right. That is, in the grayscale 50 shown in Figure 8, the density of color sample 500 in the upper left corner is the lowest, and the density of color sample 500 one step above in the lower right corner is the highest.

[0057] In contrast, reverse order means that the density changes from dark to light. In reverse grayscale 50a, the density decreases in the column direction. In the column direction of reverse grayscale 50a, the density decreases from top to bottom. Also, in reverse grayscale 50a, the density decreases in the row direction. In the row direction of reverse grayscale 50a, the density decreases from left to right.

[0058] The first test chart 5, shown in Figure 9, is a pattern with two faces each of the forward-order grayscale 50 and the reverse-order grayscale 50a, as shown in Figure 8. In the first test chart 5 shown in Figure 9, the forward-order grayscale 50 is placed on the left side of the upper row and on the right side of the lower row. In the first test chart 5 shown in Figure 9, the reverse-order grayscale 50a is placed on the right side of the upper row and on the left side of the lower row.

[0059] When printing using an inkjet method, the first test chart 5 shown in Figure 9 was converted from 16 bits to 8 bits for printing. Furthermore, when printing using the method according to the present invention, two plates with 8 bits of gradation were duotone-made from the first test chart 5 shown in Figure 9. One of these plates is a black plate made using the black plate tone curve 20. The other plate is a gray plate made using the gray plate tone curve 21.

[0060] For each color sample, the chromaticity and density in the (L*, a*, b*) color space were measured for both the forward-order grayscale 50 and the reverse-order grayscale 50a in the printed version of Test Chart 5. The average value of the measured values ​​was used to evaluate chromaticity and density.

[0061] As explained using Figure 8, the grayscale 50 image is 16-bit, but the gradation values ​​in 16 bits are large, making it difficult to intuitively grasp the degree of brightness and darkness. Therefore, when measuring the chromaticity of the color sample 500 included in the grayscale 50 in printed materials, the gradation values ​​of the color sample 500 were expressed not as 16-bit values, but as 8-bit values ​​with a single decimal point (for example, 254.5). The same procedure was followed for the reversed grayscale 50a.

[0062] Figure 10 is a diagram illustrating the chromaticity variation in an inkjet printed material. A general glossy photographic paper was used as the printing paper for the inkjet printed material. Figure 11 is the first diagram illustrating the chromaticity variation in the photographic printed material 1 according to the present invention. Figure 12 is the second diagram illustrating the chromaticity variation in the photographic printed material 1 according to the present invention. Figures 11 and 12 use different printing papers for the photographic printed material 1 according to the present invention. In Figure 11, a white cast-coated paper (e.g., Esprit®) is used as the printing paper. In Figure 12, a high-quality printing paper with an ivory color that retains the texture of the paper (e.g., Van Nuvo®) is used as the printing paper.

[0063] In Figures 10 to 12, the horizontal axis represents the grayscale value expressed as an 8-bit value with one decimal place. As mentioned above, the grayscale level of 50 is represented by RGB values, so in Figures 10 to 12, the density corresponding to the grayscale value increases from left to right. The vertical axis in Figures 10 to 12 represents chromaticity.

[0064] As illustrated in Figure 10, chromaticity fluctuations in inkjet printed materials involve short-period fluctuations similar to noise, and these fluctuations have a large amplitude. In contrast, as illustrated in Figures 11 and 12, in the photographic printed material 1 according to the present invention, these short-period, fine fluctuations similar to noise are suppressed. The fluctuation pattern of chromaticity fluctuations related to chromaticity b* is clearly different between the photographic printed material 1 according to the present invention and inkjet printed materials. This can be assumed to be due to the paper color of the printing paper and the color of the gray ink.

[0065] Figure 13 is a diagram illustrating the density transition in an inkjet printed material. A general glossy photographic paper was used as the printing paper for the inkjet printed material. Figure 14 is the first diagram illustrating the density transition in the photographic printed material 1 according to the present invention. Figure 15 is the second diagram illustrating the density transition in the photographic printed material 1 according to the present invention. Figures 14 and 15 use different printing papers for the photographic printed material 1 according to the present invention. The printing paper used in Figure 14 is a white cast-coated paper. The printing paper used in Figure 15 is an ivory-colored, high-quality printing paper that retains the texture of the paper. The horizontal axis in Figures 13 to 15 is the same as in Figure 10. The vertical axis in Figures 13 to 15 represents density.

[0066] As illustrated in Figures 13 to 15, there is no significant difference between the density transition in inkjet printed materials and the density transition in photographic printed material 1 according to the present invention.

[0067] Next, we will compare the glossiness change associated with the transition in grayscale values ​​between the photographic print 1 and the inkjet print according to the present invention. Figure 16 is a diagram illustrating the second test chart 6 used to evaluate the glossiness change associated with the transition in grayscale values.

[0068] In this embodiment, the second test chart 6 shown in Figure 16 was used to measure the gloss variation. The second test chart 6 shown in Figure 16 includes a forward pattern 6a and a reverse pattern 6b. The forward pattern 6a is located on the left side of the second test chart 6. The reverse pattern 6b is located on the right side of the second test chart 6. The meanings of forward and reverse order are as described above. One pattern includes 18 color samples 60, each corresponding to a grayscale value obtained by dividing an 8-bit grayscale from 0 to 255 in increments of 15. In one pattern, the 18 color samples 60 are arranged in a 3x6 grid.

[0069] Figure 17 illustrates the variation in glossiness in an inkjet printed material. A general glossy photographic paper was used as the printing paper for the inkjet printed material. Figure 18 is the first figure illustrating the variation in glossiness in the photographic printed material 1 according to the present invention. Figure 19 is the second figure illustrating the variation in glossiness in the photographic printed material 1 according to the present invention. Figures 18 and 19 use different printing papers for the photographic printed material 1 according to the present invention. The printing paper used in Figure 18 is a white cast-coated paper. The printing paper used in Figure 19 is an ivory-colored, high-quality printing paper that retains the texture of the paper. In Figures 18 and 19, the upper glossiness variation is the variation when varnish is applied, and the lower glossiness variation is the variation when no varnish is applied. The horizontal axis in Figures 17 to 19 is the same as in Figure 10. The vertical axis in Figures 17 to 19 represents glossiness.

[0070] As illustrated in Figure 17, in inkjet printed materials, the glossiness fluctuates wildly with changes in the tonal range. In contrast, as illustrated in Figures 18 and 19, in the photographic printed material 1 according to the present invention, there is no wild fluctuation in glossiness with changes in the tonal range, regardless of whether or not varnish is applied. In the photographic printed material 1 according to the present invention, there is a wave-like fluctuation in glossiness with changes in the tonal range, but the fluctuation in glossiness with changes in the tonal range is smooth.

[0071] From here, for reference, we will compare a printed material using a single color of black ink (hereinafter referred to as "monochrome printed material") with the photographic printed material 1 according to the present invention. In the case of inkjet printed materials, we compared them with the photographic printed material 1 according to the present invention in terms of chromaticity fluctuations, density transitions, and glossiness fluctuations. In the case of monochrome printed materials, we will compare them with the photographic printed material 1 according to the present invention only in terms of chromaticity fluctuations and density transitions.

[0072] Figure 20 is the first figure illustrating the chromaticity variation in a monochrome print. Figure 21 is the first figure illustrating the density transition in a monochrome print. Figure 22 is the second figure illustrating the chromaticity variation in a monochrome print. Figure 23 is the second figure illustrating the density transition in a monochrome print. The printing paper used for the monochrome prints in Figures 20 and 21, and Figures 22 and 23, is different. The printing paper in Figures 20 and 21 is white cast-coated paper. The printing paper in Figures 22 and 23 is ivory-colored high-grade printing paper that retains the texture of the paper. The horizontal axis in Figures 20 to 23 is the same as in Figure 10. The vertical axis in Figures 20 and 22 represents chromaticity. The vertical axis in Figures 21 and 23 represents density.

[0073] As can be seen by comparing Figures 11 and 20 and Figures 12 and 22, in terms of chromaticity fluctuations, fine fluctuations with short periods, such as noise, are suppressed more in the photographic print 1 according to the present invention than in the monochrome print. Furthermore, as can be seen by comparing Figures 14 and 21 and Figures 15 and 23, in terms of density fluctuations, fine fluctuations with short periods, such as noise, are also suppressed more in the photographic print 1 according to the present invention than in the monochrome print.

[0074] This section summarizes the results of evaluating the quality of the photographic print 1 according to the present invention. As explained above, in the case of inkjet prints, The color (chromaticity) fluctuates significantly in small cycles depending on the density (gradation value). The gloss level fluctuates wildly depending on the density (gradation value). The concentration transition is smooth. The following results were obtained.

[0075] Furthermore, in the case of the photographic print 1 according to the present invention, The color (chromaticity) does not fluctuate significantly in small increments depending on the density (gradation value). The gloss level does not fluctuate wildly depending on the density (gradation value). The density progression is not significantly different from that of inkjet printed materials. The following results were obtained.

[0076] Based on a comparison of the quality of the photographic print 1 according to the present invention with that of an inkjet print, it can be said that the photographic print 1 according to the present invention is of higher quality than the inkjet print. Furthermore, as described in the reference section, based on a comparison of the quality of the photographic print 1 according to the present invention with that of a monochrome print, it can be said that the photographic print 1 according to the present invention is of higher quality than the monochrome print. [Explanation of symbols]

[0077] 1. Photographic print 10 Base material 11 Monochrome Image Layer 110 Black Image Layer 111 Grayscale Image Layer 12 layers of varnish 20 Black Tone Curve 21 Gray version tone curve 22 Basic line 3. Printing methods for photographic prints 30 Monochrome image layer formation process 300 Ink Image Layer Formation Process 301 Gray image layer formation process 31. Varnish layer formation process 4. Original image 5. First Test Chart 50 Grayscale 6. Second Test Chart

Claims

1. A substrate and a monochrome image layer formed by offset printing using duotone platemaking are stacked, The monochrome image layer includes a gray image layer formed using gray ink with a low concentration of black pigment, and a black image layer formed using black ink with a high concentration of black pigment. The gray tone curve used for platemaking of the gray plate and the black tone curve used for platemaking of the black plate are each made into a curve that arcs from a starting point where the density gradation value is the minimum value and the percentage of halftone dots is the minimum value to an ending point where the density gradation value is the maximum value and the percentage of halftone dots is the maximum value. In the gray tone curve, the slope in the bright areas is made greater than the reference line connecting the starting point and the ending point by a straight line, and the slope from the midtones to the dark areas is made smaller than the slope in the bright areas. In the black tone curve, the slope in the bright areas is made smaller than the reference line, and the slope from the midtones to the dark areas is made greater than the reference line. As a result, in the gray image layer, the bright areas to the midtones are reproduced with 8-bit equivalent gradation, improving the tonal reproduction of the bright areas, and in the black image layer, the midtones to the dark areas are reproduced with 8-bit equivalent gradation, lowering the tonal reproduction of the bright areas and improving the tonal reproduction of the midtones. A photographic print characterized by the following features.

2. The photographic print according to claim 1, characterized in that the black ink is an ink using carbon black as the black pigment, and the gray ink is a lightfast ink using carbon black as the black pigment.

3. A photographic print according to claim 1 or 2, characterized in that a varnish layer using a glossy varnish is laminated on the surface.

4. The photographic print according to claim 3, characterized in that the varnish is UV varnish.

5. A photographic print according to any one of claims 1 to 4, characterized in that the substrate is made of paper that has a similar texture to photographic paper used in silver halide photography.

6. This includes a monochrome image layer formation step in which a monochrome image layer is laminated onto a substrate using double-tone offset printing. The monochrome image layer formation process creates a curved shape that arcs from a starting point where the density gradation value is at its minimum and the percentage of halftone dots is at its minimum, to an ending point where the density gradation value is at its maximum and the percentage of halftone dots is at its maximum, and by making the slope of the bright areas smaller than a reference line connecting the starting point and the ending point with a straight line, and making the slope from the midtones to the dark areas larger than the reference line, the midtones to the dark areas are reproduced with 8-bit equivalent gradation, thereby reducing the tonal reproduction of the bright areas and increasing the tonal reproduction of the midtones, and a black plate is made, and the black The process includes a process of forming a black image layer using a plate and black ink with a high concentration of black pigment, and a process of producing a gray plate that is curved in an arc from the starting point to the ending point, with the slope of the bright areas being greater than the reference line, and the slope from the midtones to the dark areas being smaller than the slope of the bright areas, thereby reproducing the range from bright to midtones with 8-bit equivalent gradation and improving the tonal reproduction of the bright areas, and a process of forming a gray image layer using the gray plate and gray ink with a low concentration of black pigment. A method for printing photographic prints characterized by the following features.

7. The method for printing a photographic print according to claim 6, characterized in that the black ink is an ink using carbon black as the black pigment, and the gray ink is a lightfast ink using carbon black as the black pigment.

8. A method for printing a photographic print according to claim 6 or 7, characterized by including a varnish layer formation step of laminating a varnish layer using a glossy varnish onto the surface.

9. The method for printing a photographic print according to claim 8, characterized in that the varnish is UV varnish.

10. A method for printing a photographic print according to any one of claims 6 to 9, characterized in that the substrate is made of paper having a similar texture to photographic paper used in silver halide photography.

Images