JP2506191B2 - Photo printing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photographic printing method in which exposure control is performed using color information of a subject recorded at the time of shooting.

[Prior Art] In photographic printing, the frames recorded on the photographic film are measured to obtain the average transmission densities of the three primary colors (red, green, blue), and the exposure exposure amount of the three colors is determined according to these average transmission densities. Are in control. This exposure control is called the LATD method, and determines the printing exposure amount of each color so that the result of integrating the three primary colors of the print photograph is gray.

The color of the recorded image may change significantly depending on the aging of the photographic film, the subject, and the shooting conditions (illumination light, reciprocity law failure, etc.). For such a frame
When the exposure is controlled by the LATD method, it is impossible to produce a print photograph with good color balance. Although the color of the recorded image changes depending on the color development characteristics of the photographic film and the color of the base, color correction for the film type has been conventionally performed by inputting the information of the film type before printing the photograph. There is.

In order to deal with the above-mentioned problems, it is possible to project the shooting light quality in a spot shape at a place other than the frame of the photographic film at the same time as shooting, and to measure this spot part during photo printing and use it for setting print conditions. Has been proposed (Japanese Patent Laid-Open No. 51-117632). Also, through the optical wedge, the light from the main illumination light source of the subject is projected between the frames, and the density is measured during photoprinting so that this part is reproduced in an achromatic or standard color. A method for determining the color printing exposure amount has also been proposed (JP-A-52-13333).

[Problems to be Solved by the Invention]

The above-mentioned conventional method measures the illumination light recorded on the photographic film and determines the printing exposure amount so that the illumination light is finished in gray. However, it is very difficult to record only the illumination light, excluding the influence of the reflected light of the subject. For example, in the case of a photograph in which a person wearing red is standing on a green grass, or a subject with uneven color, such as a clear sea or mountain subject, if the recorded illumination light is finished in gray, the subject color will change. It will be different from.

An object of the present invention is to provide a photographic printing method capable of faithfully reproducing the average color tone of a subject.

[Means for solving the problem]

In order to achieve the above-mentioned object, the present invention measures the whole or a part of a subject with a three-color sensor at the time of taking a photograph, records the obtained color information, and reads the color information at the time of printing the photograph. The exposure is controlled.

Although there are various examples of using the color information in photo printing, it is preferable to control the printing exposure amount of the three colors so that the same area of the subject and the reproduced image is reproduced in the same color.

Further, in the method of controlling the exposure so that the skin part of the person recorded on the photo film, for example, the face is reproduced in the original skin color, it is necessary to correctly detect the skin part recorded on the photo film. is there. In this method, the skin color is defined in advance, and it is determined whether the color of each pixel is included in the defined skin color range to extract the skin color area. However, since the skin color recorded on the photo film changes depending on the type of the photo film, the passage of time, and the illumination state of the subject, the skin color cannot be detected with high accuracy. In such a case, the color of each pixel is corrected using the color information, and it is determined whether or not the corrected color is included in the defined skin color range to detect the skin color portion with high accuracy. be able to.

[Action]

In the present invention, since the correct color of the image recorded on the photographic film can be found by using the color information recorded at the time of photographing, the color of the subject can be faithfully reproduced.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1 showing an outline of a camera, a photographing lens 10
Is composed of an optical system 10a and a lens mirror copper 10b that holds the optical system 10a, and moves along the optical axis 11 to perform focus adjustment by a manual or autofocus mechanism. A shutter mechanism 12 is arranged behind the taking lens 10. The shutter mechanism 12 includes, for example, two shutter blades.
The density shutter blades 13 and 14 are provided with notches 13a and 14a, respectively. When the movable pin 16 moves toward the fixed pin 17 by the drive mechanism 15, the shutter blades 13 and 14 move in a direction away from the fixed pin 17 and overlap the notches 13a and 14a. The overlapping portions of the notches 13a and 14a are opened, and the light passing through the notches 13a and 14a is incident on the photographic film 18, and the image of the subject is imaged therein.

The photometric unit 20 measures the three colors of the subject light to measure the average color of the subject. By appropriately setting the light receiving angle of the photometry unit 20, the whole or a part of the photographing screen, for example, the central portion can be measured. The photometric unit 20 includes a red sensor 21 for photoelectrically converting red light, a green sensor 22 for photoelectrically converting green light, and a blue sensor 23 for photoelectrically converting blue light.
And a lens 24 blue 26 arranged in front of each sensor 21-23. As is well known, each sensor has a filter of a color corresponding to the color light to be measured in front of the photoelectric conversion element.

As the sensors 21 to 23, those having a spectral sensitivity equal to the sensitivity distribution of human eyes (e.g., equal to a tristimulus value curve) are preferably used. In this case, it is possible to finish the subject illuminated by an artificial light source such as a fluorescent lamp or a tungsten lamp with the same color as when viewed by eyes.

The outputs of the sensors 21 to 23 are amplified by the amplifier 28 and then sent to the barcode conversion unit 29 where they are converted into barcode data. This barcode data is the driver
It is sent to the barcode recording device 31 via 30. A bar code recording device 31 of this embodiment, a liquid crystal display 32 for displaying a bar code, and a flash discharge tube 33 for illuminating the bar code recording device 31 are provided.
The three-color photometric data of the shooting light is imprinted as a bar code between a and the film edge.

FIG. 2 shows an example of a photographic film on which a bar code is recorded. Perforations 18b are perforated at regular intervals in the photographic film 18, and the perforations 18b are detected by a sensor of a winding stop device to feed one frame. Perforation 18b
On the other side of, red photometric data represented by a bar code 35,
The green photometric data 36 and the blue photometric data 37 are imprinted, and converted into a visible image by photographic development.

FIG. 3 shows a photographic printer. White light emitted from the light source 40 passes through a cyan filter 41, a magenta filter 42, and a yellow filter 43, and then enters a mixing box 44. In these color correction filters 41 to 43, the amount of insertion into the optical path 46 is adjusted by the filter adjustment unit 45,
Thereby, the three-color light components of the printing light and the intensity thereof are adjusted. The mixing box 44 is formed by attaching diffuser plates to both ends of a rectangular tube whose inner surface is a mirror surface.

The film carrier 50 is placed in the print position, and the developed photographic film 18 is set and illuminated by the holes passing through the mixing box 44. In order to ensure the flatness of the photographic film 18, a film mask 51 is provided above the print position. This film mask
As is well known, the 51 has an opening corresponding to the size of the frame, and when the photo film 18 is transferred, the photo film 18 is lifted by a solenoid (not shown) and presses the photo film 18 during printing. .

A bar code reader 52 is arranged in front of the print position, and when sent to the print position, the photometric data 35 to 37 recorded in each frame are read. The read photometric data is decoded by the decoder 53 and then sent to the calculation unit 54.

Further, a scanner 59 composed of a lens 57 and an image area sensor 58 is disposed diagonally above the print position, and the transmitted light at each point of the frame set at the print position is separated into three colors. The three-color signal of the scanner 59 is converted into a digital signal by the A / D converter 60 and then logarithmically converted by the logarithmic converter 61. The three-color density signal of each point obtained by this logarithmic conversion is sent to the calculation unit 54.
The calculation unit 54 uses the photometric data 35 to 37 to calculate the printing exposure amounts of the three colors so that the average color of the subject and the average color of the print photograph will be the same.

For example, the following formula is used as a printing exposure amount calculation formula, and the printing exposure amount E _i (i is one of red, green, and blue)
Is calculated).

logE _i = (Kl _i + K2 _i ) + K3 _i (D _i −D N _i ) ... (1) Here, each symbol is as follows.

K1: exposure required to properly finish a normal control negative K2: correction value obtained from photometric data K3: slope value D: average transmission density of frame to be printed DN: average transmission density of normal control negative K2 Is for correcting the color depending on the content of the frame. For example, in the case of a sea scene, the printing exposure amount is determined so that the three-color average value of the print photograph becomes blue of the subject scene. Incidentally, since the correction value K2 is not used conventionally, if K2 is set to zero in the arithmetic expression (1), the conventional printing exposure amount arithmetic expression is obtained.

K2 _i = F {(scene color i obtained from three-color photometric data)
-(Scene color i equivalent to normal control negative)} (2) The function F of the equation (2) is for converting the three-color photometric data between scenes into a print density difference, For example, the following two color shifts centered on green may be used.

K2 _i = (logL _i −logL _G ) − (logLN _i −logLN _G ) ... (3) Here, each symbol is as follows.

L _i : Three-color photometric data L _G : Green photometric data LN _i : Photometric data of a scene equivalent to a normal control negative (usually gray or average data of many scenes is used, which is a constant value) LN _G : Green photometric data of a scene corresponding to a normal control negative (usually gray or average data of many scenes is used, which is a constant value.) The calculated exposure exposure signal for each color is the controller 55.
Is sent to the filter adjusting unit 45 after being converted into a filter set position signal.

A printing lens 65 is arranged above the printing position, and the image of the set frame is enlarged and projected onto the color paper 67 arranged behind the paper mask 66. A shutter 69 whose opening / closing is controlled by a shutter drive unit 68 is arranged between the printing lens 65 and the color paper 67.

Next, the operation of the above embodiment will be described. When taking a picture, the composition is aimed at the main subject, and then the taking lens 10 is moved along the optical axis 12 to adjust the focus. When the release button (not shown) is pressed after the focus adjustment, the drive mechanism 15 operates the shutter mechanism 12 to record the image of the subject on the photographic film 18.

On the other hand, the three-color sensors 21 to 23 of the photometric unit 20 photoelectrically convert the light from the subject and send the red photometric value, the green photometric value, and the blue photometric value to the barcode conversion unit 29 via the amplifier 28. The bar code conversion unit 29 converts a red photometric value, a green photometric value, and a blue photometric value into a bar code at the same time as or before or after taking a photograph, and sends the bar code to the driver 30. This driver 30
Drives the barcode recording device 31, and first displays the barcode representing the three-color photometric data on the liquid crystal display 32.
When this display becomes stable, the flash discharge tube 33 is caused to emit light, and the photometric data 35 to 37 are imprinted on the peripheral portion of the screen 18a as shown in FIG.

When the photographing of one photo film 18 is completed, the photo film 18 is taken out of the camera and submitted to a photo processing laboratory. At the photo lab, the photo film 18 is developed to convert each frame recorded as a latent image and the data recorded for each frame into a visible image.

The developed photographic film 18 is loaded into the film carrier 44 of the photographic printer shown in FIG. The photo film 18 is recorded on the periphery of the frame 18a by the bar code reader 52 when it is transferred on the film carrier 50. The red photometric data 35, the green photometric data 36, and the blue photometric data 37 are recorded.
Is read. The read data 35-37 is the decoder 53
After being decoded by, the data is sent to the calculation unit 54.

When set to the print position from the top 18a, the scanner 59 measures red, green, and blue transmitted light for each point on the top 18a. The photometric values of these three colors are A / D
After being subjected to the conversion processing and the logarithmic conversion processing, they are sent to the arithmetic unit 54. The calculation unit 54 calculates the average transmission density D _i of the frame by arithmetically averaging the three-color densities of the respective pixels. Also, the three-color photometric data L _i is substituted into the arithmetic expression (3) to correct the correction amount.
Calculate K2 _i . Using this correction amount K2 _i and the average transmission density D _{i of the} frame to be printed, the printing exposure amount E _i is calculated from the arithmetic expression (1).

After calculating the printing exposure amount E _i , the controller 55 adjusts the insertion amount of the color correction filters 41 to 43 into the optical path 46 according to the printing exposure amount. After this filter adjustment, the shutter 69 is opened for a fixed time, and the frame 18a is printed and exposed on the color paper 67. Thereafter, in the same manner, each frame is sequentially printed on the color paper 67.

The following formula may be used as the printing exposure amount calculation formula.

_{logE i = Kl i + K2 i} (D i -Dn i) ···· (4) Dn i = DN i + G {( scene determined from three color photometric data color i) - (scene corresponding to the normal control negative Color i)} (5) In equation (5) including this function G, the two types of color i may be a color shift from the green color represented by equation (3). If the conventional printing exposure calculation formula is used, for example, in a sea scene, D _B is larger than D _R and D _G , the blue printing exposure E _B becomes long, and the sea scene becomes gray. from correction it is necessary to shorten the blue print exposure amount E _B. In this embodiment, since Dn _i has the same color as the sea scene and no correction for finishing to gray is applied, a blue sea can be reproduced.

Although the color of the pixels recorded on the photographic film changes depending on the type of the photographic film and the main light source, it can be corrected to the correct color by using the three-color photometric data L _i .
FIG. 4 shows the function of the arithmetic unit for performing this color correction. The memory 73 stores the three-color density f _ij (j is the number of the photometric point) of each point (pixel) on the screen measured by the scanner 59. The three-color density f _ij is read during the exposure amount calculation and sent to the color density correction calculation unit 74. This color density correction calculation unit 74 is read by the bar code reader 52 and stored in the memory.
Using the three-color photometric data L _i stored in 75 and the average three-color density f _{i of} the screen 18a, the three-color density Df _ij of each pixel is corrected and calculated from the following equation. Where the average three-color density F _i is the three-color sensor
It is the same as the photometric range of 21 to 23. For example, when the three-color photometric data L _i is obtained from all the subjects, the average three-color density F _i is obtained by photometrically measuring the entire screen 18a.

Df _ij = (F _i −L _i ) + f _ij (6) The corrected three-color density Df _ij is sent to the skin color pixel extraction unit 76, and the skin color pixels are extracted here. The extraction of the skin color is performed with reference to the data defining the skin color range stored in the memory 77. This flesh color can be defined by an ellipse in Cartesian coordinates with the density differences (RG) and (GB) as axes, and when each pixel is included in the ellipse, this pixel is a flesh color. It is determined that there is. In addition to this ellipse, the skin color range can be defined by a rectangle, a rhombus, or the like.

The face area determination unit 78 determines a closed area composed of skin color pixels as a face area, and obtains the position of the pixel in the face area. The position coordinates of the face area are sent to the characteristic value extraction unit 80, and the characteristic value of the arithmetic expression for determining the exposure amount for printing is extracted with the finish of the face being emphasized. That is, the feature value extraction unit 80 reads the color densities of the pixels in the face area and calculates the average value from the color densities of these pixels. Furthermore, the feature value extraction unit 80,
It also calculates the maximum and minimum values within the screen, or the average density of specific areas such as the central and peripheral parts of the screen. The obtained feature value is sent to the calculation unit 82, and the baking exposure amount calculation formula 82 that emphasizes the skin color is calculated.
is assigned to a. On the other hand, the characteristic value extraction unit 81 extracts the characteristic value used in the general printing exposure amount calculation formula 82b. Specific examples of these baking exposure amount calculation formulas are described in detail, for example, in JP-A-62-189456.

The calculation formula selection unit 83 selects the printing exposure amount calculation formula 82a when the face area exists in the frame 18a, and selects the printing exposure amount calculation formula 82b when it does not exist, and this selection is made. The printing exposure amount E _i is calculated from the arithmetic expression.

As described above, film type (sensitivity, γ, base concentration)
, The colors of the images recorded on the photographic film are different even for the same subject. Therefore, conventionally, it is necessary to check whether the color of the image is the color of the subject itself, the color of the light source, or the type of film, and change the exposure control according to the result. In the present invention,
Since all or part of the color of the shooting scene has been recorded, it is appropriate to finish it to a preferable color that is the same as or approximate to the subject color obtained from the three-color photometric data, without considering the cause of the change in color density. It is possible to produce a print photograph with a good color balance. With this printing method,
A table having (logL _i −logL _G ) as an address and logE _i as data is prepared, and the printing exposure amount E _i can be obtained from the three-color photometric data L _i by referring to this table. Of course, the table is prepared in consideration of the sensitivity change of the color paper and the development performance change of the color paper.

In the above-described embodiment, the three-color photometric data is recorded in the form of a bar code on the photographic film as the color information, but instead of this, codes representing "0" and "1" depending on the presence or absence of the optical mark may be used. . This code can be recorded, for example, on a photographic film using light emitting diodes. Also,
The IC card may be set in the camera and the three-color photometric data may be recorded or recorded in the cartridge. Further, the present invention is also applicable to the case where the three-color photometric data is written together with the image data in a memory such as a magnetic floppy in an electronic still camera and the image is printed on a color paper or the like as a hard copy.

〔The invention's effect〕

In the present invention having the above-described configuration, the color information of the subject is recorded at the time of shooting, and the exposure control is performed using this color information at the time of printing the photograph, so that the reproduced image can be finished in the same color as the subject.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a photographic camera embodying the present invention. FIG. 2 is an explanatory diagram showing an example of data recording of a photo film. FIG. 3 is a schematic diagram of a photographic printer embodying the present invention. FIG. 4 is a functional block diagram of an arithmetic unit used in the embodiment for performing skin color control. 10 …… Shooting lens 18 …… Photo film 21 …… Red sensor 22 …… Green sensor 23 …… Blue sensor 31 …… Bar code recorder 32 …… LCD display 33 …… Flash discharge tube 35 …… Red Photometric data 36 …… Green photometric data 37 …… Blue photometric data 52 …… Bar code reader 59 …… Scanner 67 …… Color paper.

Claims (2)

(57) [Claims] 1. A method in which all or a part of a subject is measured with a three-color sensor at the time of taking a photograph, the obtained color information is recorded, and the color information is read at the time of printing a photograph and used for exposure control. Photographic printing method. 2. A photometric measurement of all or a part of a subject with a three-color sensor at the time of taking a photograph, and the obtained color information is recorded. When the photograph is printed, the color information is read and the same area of the subject and the reproduced image is read. A photographic printing method characterized in that the exposure amounts of three colors are controlled so that the same color is reproduced.