JPH04348335A - Method for deciding photograph printing exposure - Google Patents

Abstract

PURPOSE:To stably and efficiently produce a photographic print having fixed quality and to decide exposure for a photographic original picture with high reproducibility by correcting the exposure with the specified statistic of an original picture. CONSTITUTION:The original picture recorded on a photographic film F is color- separated to respective colors B, G and R and scanned by a scanning part 22. The image signals of the respective colors B, G and R obtained by the scanning part 22 are transmitted to an image processing part 24, A/D converted and shaped to specified form of image density information, then transmitted to an information processing part 26. The information processing part 26 obtains the specified statistic based on the image density information, calculates the correction value for each original picture based on the statistic, and the signal of the correction amount is transmitted to an exposure control part 30 through a communication line 28. The average transmitted light of the respective colors B, G and R is obtained for the respective original pictures by an exposing part 32, and the exposure is calculated based on the obtained data and the correction amount transmitted from the information processing part 26 by an exposure control part 30.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for determining the exposure amount for photographic printing when processing photographs, and more specifically, the present invention relates to a method for determining the exposure amount for photographic printing when processing photographs. , and correct the exposure amount based on the average transmission density of the original image using the correction amount for each original image determined based on this statistic value, and create an appropriate photographic print regardless of the tone reproduction characteristics of the photographic film. This invention relates to a method for determining photographic printing exposure.

0002

[Prior Art] In general photography, blue (B), green (G), and red (R) (hereinafter simply B,
It is known as a rule of thumb that the average reflectance of the three primary colors (denoted as G and R) is approximately constant. Therefore, in conventional photo printing equipment, the average transmission density (L) of the entire area of the original photo is
By measuring the ATD) and determining the exposure amount in photographic printing based on the measured average transmission density, the amount of exposure given to the B, G, and R color photosensitive layers of the photographic paper is controlled to a constant value, and color balance is achieved. I try to make good photographic prints.

[0003] At this time, there is a drawback that it is difficult to obtain an appropriate photographic print if the luminance distribution or color distribution of the subject is uneven. These original photographic images are called subject feria, particularly when the cause is bias in the luminance distribution of the subject, it is called density feria, and when the cause is bias in the color distribution, it is called color feria. As a known technique aimed at automatically adjusting the exposure amount for density ferrets, the following technique disclosed in Japanese Patent Publication No. 56-2691 can be mentioned. That is, an original image on a photographic film is scanned, characteristic values are determined for each area of the image from the image density obtained by scanning, classification is performed based on the characteristic values, and predetermined characteristic values are determined for each classification. The exposure amount for the original image is adjusted by the function.

[0004] Also, as a known technique for adjusting the exposure amount for color feria, for example, C.I. J.
Hartleson and R. W. Written by Huboi
”Exposure Determination M
methods for Color Printing
:The concept of Optimum C
orrection Level”, J.SMPTE
, 65, 205-215 (1956).

[0005] In this published example, the exposure is adjusted according to LATD for the original photograph taken of a standard subject.
Full correction, in which the amount of exposure given to each color photosensitive layer of photographic paper is set to a constant value, is considered effective. When the photographic exposure is appropriate, LAT is effective against subject feria.
No-correction, which involves exposure with a constant light flux or exposure time regardless of D, is effective. Furthermore, as a compromise, lower correction, which is an intermediate control method between the two, is actually appropriate, and the optimum correction level should be selected based on the overall quality of the photographic print.

[0006] In recent years, it has become common for photo printing apparatuses to be equipped with several selectable collection levels.

Furthermore, E. Goll, D. Hill and W. Written by Severin “Modern Expo
Sure Determination for Cus
tumizing Photofinishing P
rinter Response”, JAPE, 5, 9
3-104 (1979), the effect of the color temperature of the photographic lighting is significant for certain hues in the chromaticity calculated based on the density of the original photograph, so the collection level is adjusted depending on the hue. However, it is stated that in order to obtain photographic prints with appropriate color balance, it is necessary to adjust the density, which is the standard for lower correction.

[0008] Normally, in a photo printing apparatus using the LATD control method, changes in the density of the B, G, and R colors of the original photo are caused by differences in either the tone reproduction characteristics of the photographic film or the color distribution of the subject. It is not possible to automatically identify whether this is occurring. For this reason, exposure conditions are set in advance for each type of photographic film.
The set exposure conditions are changed depending on the type of photographic film to be printed.

However, with the increase in the variety of photographic films in recent years, the necessity of setting and switching exposure conditions as described above has become a major factor hindering the rationalization of the photographic printing process.

Furthermore, even with the same type of photographic film, photographic prints with proper color balance may not be obtained under the set exposure conditions due to deterioration of tone reproduction characteristics due to the state of latent image storage. This is a major obstacle to the stable and efficient production of photographic prints of a certain quality.

As described above, in order to appropriately determine the exposure amount in photographic printing, the density, which is the standard for color correction, must be determined based on the characteristics of each photographic film.

[0012] As an example of solving this problem,
No. 6741 can be mentioned. In this example, photographic film is separated into three primary colors and scanned, and the density difference and neutral density between two sets of two colors are determined from the image density of each color obtained.
The method is characterized in that a value unique to the photographic film is derived from the functional relationship between the two sets of density differences and the neutral density, and is associated with exposure control.

[0013] This method has the disadvantage that the calculation becomes extremely complicated because it is necessary to approximately find the distribution of the concentration difference with respect to the neutral concentration as a function of the neutral concentration. For example, an example is shown in which the distribution of concentration difference is represented by a quadratic or cubic polynomial of neutral concentration, and its coefficients are calculated by the method of least squares, but this example requires a large amount of calculations. I need. Furthermore, a method for calculating the average value of the density difference corresponding to the neutral density is also shown, but if there is no corresponding data, it is necessary to perform interpolation based on the relationship before and after the data.

[0014] Further, as an example of solving such problems in arithmetic processing, Japanese Patent Laid-Open No. 2-6939 can be mentioned. This method separates and scans multiple photographic originals, determines the cumulative density function of the image density of each color, and determines the exposure amount based on this function. Since it is based on frequency, calculation is extremely simple and can be realized by inexpensive calculation means using a general microprocessor or the like.

[0015]

In these examples, the exposure amount is determined based on the image density obtained by scanning. Photographic film is generally capable of recording images over an extremely wide density range, but on the other hand, imaging devices such as CCDs generally have a drawback of having a narrow photometric dynamic range. Therefore, it is difficult to accurately and stably measure the density of a photographic original using these image sensors and to determine the exposure amount for this photographic original with high reproducibility. In addition, when trying to obtain a wide dynamic range, it is necessary to use an extremely expensive image sensor that has photoelectric conversion elements with a wide light-receiving area arranged in a linear or planar manner. Due to the large size, there is a problem that the imaging system including the imaging optical system and the color separation means must be large-scale. In this case, there is a further disadvantage that the outputs of the plurality of light receiving elements must be switched at high speed and signal processing with a high S/N ratio is required, which inevitably makes the circuit configuration complicated and expensive.

[0016] Furthermore, in these methods, prior to exposure,
Since it is necessary to scan the photographic original in advance to determine the exposure amount, as shown in the above example, the apparatus for implementing these methods has a mode in which the scanning stage and the exposure stage are separated. In this manner, a major problem is faced when performing a rewrite. In other words, in the case of reprinting, it is assumed that a photographic print equivalent to the photographic print obtained in the first printing can be obtained, so in the above method and embodiment, the imaging system used for the first printing is The original photograph to be reprinted must be scanned again. However, in the case of reprinting, the photographic film is usually cut into short lengths, and it is not easy to continuously scan and expose such photographic film with a device in which the scanning stage and the exposure stage are separated. do not have.

Furthermore, it is normal for the illumination light applied to the photographic original in the exposure system to fluctuate due to changes over time in the illumination light source and illumination optical system, and also that the dye image of the photographic original is affected by the action of radiant heat from the illumination in the exposure system. is known to deteriorate during exposure, but in a mode where the scanning stage and the exposure stage are separated spatially or temporally, it is impossible to detect these fluctuations at the time of exposure and adjust the exposure amount. be.

The present invention has been made in view of the above-mentioned problems, and allows exposure conditions to be set in advance for each type of photographic film, and for printing photographs without having to change the set exposure conditions according to the type of photographic film to be printed. It is possible to appropriately determine the exposure amount during printing, and it also provides a constant level of protection against deterioration of characteristics due to latent image storage conditions, fluctuations in illumination light in the exposure system, and deterioration of image characteristics during exposure. An object of the present invention is to provide a method for determining a photographic printing exposure amount, which can stably and efficiently produce high-quality photographic prints.

Furthermore, the present invention makes it possible to determine the exposure amount for the original photograph with high reproducibility even when the original photograph is scanned using a simple and inexpensive imaging system, and to easily perform reprinting. The purpose of the present invention is to provide a method for determining the exposure amount for photographic printing.

[0020]

[Means for Solving the Problems] In order to achieve this object, the photographic printing exposure determination method of the present invention measures the average transmission density of an original image formed on a photographic film, and based on this density, it measures the average transmission density of an original image formed on a photographic film. In a photographic printing exposure determination method that determines the exposure amount, a plurality of original images formed on a photographic film are scanned before measuring the average transmission density, and a predetermined statistical value is calculated from the image information of the plurality of original images obtained thereby. seek,
Furthermore, image characteristic values are calculated from the image information of each original image,
Next, a correction amount is determined from the statistical amount and the image characteristic value, and the exposure amount is corrected using this correction amount.

Further, the predetermined statistic is a cumulative density function of image information of a plurality of original images.

Furthermore, the above-mentioned characteristic value is an average value of the image information of each original image.

Further, the characteristic value is an inverse function of the cumulative density function of the image information of each original image.

[0024] Furthermore, the plurality of original images described above are original images that span a plurality of photographic films.

According to the present invention, the plurality of original pictures are original pictures spanning a plurality of photographic films belonging to a specific type.

[0026] The plurality of original images are original images spanning a plurality of photographic films belonging to a predetermined classification.

Furthermore, this variety is identified by reading the bar code attached to the photographic film.

[0028]

[Operation] In the photographic printing exposure determination method of the present invention, a plurality of original images formed on a photographic film are scanned, and a predetermined statistical amount is obtained from the image information of the obtained plurality of original images. Information regarding the tone reproduction characteristics of the film is derived. Furthermore, the image characteristic values are calculated from the image information of each original image, and the amount of correction is determined from the above statistics and image characteristic values. It is possible to obtain the correct amount of correction.

In addition, the exposure amount is determined based on the average transmission density of the original image, and the average transmission density of the original image is measured at the time of exposure, so that changes in density due to fluctuations in illumination light in the exposure system and image deterioration during exposure can be avoided. can be detected and the exposure amount can be adjusted. In addition, here, since it is sufficient to measure the average transmission density of the original image for each color of B, G, and R,
A photometric element with a large light-receiving area can be used. As a result, a sufficient dynamic range can be obtained in photometry, and images formed on photographic film can be recorded over a wide range of densities. The exposure amount for the original image can be determined. Moreover, since this measurement can be performed independently during the exposure step, there is no need to go through the scanning step again when reprinting.

The exposure amount determined based on the average transmission density of the original image is corrected by the above correction amount. Therefore, in the end, it is possible to obtain an appropriate exposure amount that takes into account the tone reproduction characteristics of the photographic film, the characteristics of individual original images, and various fluctuations during exposure. Furthermore, since the change in the amount of correction mentioned above is generally extremely small compared to the change in exposure amount based on the average transmission density of the original image, CCD is a typical imaging system for scanning the original image. It is possible to use inexpensive elements, and a simple circuit can also be used for signal processing.

[0031] Furthermore, the type of photographic film can be identified by reading the barcode attached to the photographic film;
Based on the result of this identification, the predetermined statistics are accumulated across a plurality of photographic films for each specific product type or for each product type belonging to a predetermined classification. By using this accumulated statistics as an auxiliary, it is possible to solve cases where the number of original images formed on the photographic film is too small to obtain sufficient statistics, or when the original images formed on this photographic film are extremely similar to a specific subject. Even if the image is biased, an appropriate amount of correction can be determined based on the tone reproduction characteristics of the photographic film.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the photographic printing exposure amount determining method of the present invention will be described below with reference to the drawings.

FIG. 1 shows the construction of a 135 photographic film that has been subjected to a printing process.

In the figure, a plurality of photographic films F that have been developed to form original images (groups) G are spliced together by a splice 10 to form a roll. The roll of photographic film F has a notch (group) 1 indicating the center position of the original image in the notch process before the photographic printing process.
2 is placed at its end. Additionally, well-known perforations (groups) P are arranged in advance at this end. By detecting this notch 12, conveyance control such as positioning of the photographic film F in subsequent steps is performed. As shown in the figure, the photographic film F is attached with a bar code 14 indicating its type. Note that the photographic film F in this example is not limited to the 135 photographic film, but may be any other photographic film.

The roll-shaped photographic film F thus processed is subjected to a printing process in a photoprinting apparatus.

FIG. 2 shows the configuration of a photographic printing apparatus.

The photographic film F is set on the spool 20 and wound onto the spool 20 through a predetermined transport path. A scanning section 22 is provided in the middle of the path, whereby the original image recorded on the photographic film F is scanned in B, G, and R.
The image is separated into each color and scanned. The image signals of B, G, and R colors obtained in the scanning section 22 are sent to the image processing section 24, where they are A/D converted and shaped into image density information in a predetermined format, and then sent to the information processing section 26. Ru.

The image density information is subjected to the processing described below in the information processing section 26, and as a result, a correction amount is calculated for each original image, and a signal of this correction amount is transmitted to the exposure control section 30 through the communication line 28. Ru. The photographic film F that has passed through the scanning section 22 is provided between the scanning section 22 and the exposure section 32 in order to absorb the difference in conveyance speed of the two photographic films F and at the same time scan a plurality of original images in advance before exposure. The light is sent to the exposure section 32 through the buffer section 34 . Note that the transport path between the scanning section 22 and the exposure section 32 has a maximum length corresponding to 135 photographic films with 24 exposures, and thus 135 photographic films with 24 exposures.
Image density information corresponding to almost all the original images G recorded on the book can be obtained prior to exposure.

Each original image formed on the photographic film F is positioned by the exposure section 32, and is irradiated with light from a light source 36, which is then illuminated as uniform light by a diffusion section 38. Furthermore, an image is optically formed on the photographic paper 40 by the lens 54 and exposed.

At this time, the photometric filters 4 for each color of B, G, and R are
The average transmitted light of each color of B, G, and R of the original image passes through photodiodes 44a, 44b, and 44c through 2a, 42b, and 42c.
The light is received by. B, G which photoelectrically converted this amount of received light
, R are supplied to the exposure control unit 30 and further subjected to A/D conversion. As a result, the exposure amount is calculated based on the obtained data and the correction amount supplied from the information processing unit 26. It will be done.

The exposure amount obtained here is determined in the exposure control section 30 by the yellow (Y)
, Masenda (M), and cyan (C), and the operating time of the shutter 52 disposed below the exposure section 32. The cut filters 50a, 50b are cut according to the operating time.
, 50c and a shutter 52 are inserted into the exposure optical path, and the exposure given to each color photosensitive layer of the photographic paper 40 is adjusted. After this exposure is completed, the photographic paper 40 is conveyed a predetermined distance in preparation for the next exposure, and the photographic film F is conveyed in order to position the original image G to be printed next in the exposure section 32.

In this way, the original images G recorded on the photographic film F are sequentially subjected to a printing process.

FIG. 3 shows the structure of the scanning section 22 in detail.

In the scanning section 22, the light emitted from the light source 59 is formed into substantially parallel light by the lens 60. This parallel light is processed by color separation filters 62a, 62b, and 62c arranged parallel to each other along the transport direction of the photographic film F.
It is separated into each color.

In this way, the light is separated into B, G, and R colors, and the light that passes through the slit 64 separates the photographic film F.
is illuminated. The light transmitted through photographic film F is B,G
, R are photoelectrically converted by CCD line sensors 68a, 68b, and 68c arranged at positions corresponding to the illumination lights of each color. Note that the CCD line sensors 68a, 6
Both of 8b and 68c are composed of 2048 pixels and use a one-dimensional imaging device capable of scanning over a length of 32 mm in the width direction of the photographic film F.

[0046] As a result, the width of the photographic film F
Main scanning was performed for 2 mm, and the B, G obtained here
, R are supplied to the image processing section 24. Further, the notch 12, splice 10, and bar code 14 attached to the photographic film F are detected by detectors 70a, 70b, and 70c, respectively, and these detection signals are supplied to a conveyance control circuit 72. Transport control circuit 72
processes these detection signals and sends the results as notch signals, splice signals, and bar code signals to the image processing section 24 and the information processing section 26 via the system bus 74, as well as to the pulse motor 75. is driven to control the conveyance of the photographic film F, and supplies the conveyance pulse to the image processing section 24 as a synchronizing signal for sampling the image signal.

[0047] The photographic film F is operated by a pulse motor 75.
The paper is transported at a rate of 0.25 mm/pulse, and sub-scanning is performed accordingly.

FIG. 4 shows the detailed configuration of the image processing section 24. The image processing section 24 performs the following signal processing.

The image signal supplied from the scanning section 22 is amplified by the amplifier circuit 80 and then sent to the sample and hold circuit 8.
2 and A/D converter 84,
converted into a digital signal. Note that the timing control circuit 86 includes CCD line sensors 68a and 68 in the scanning section 22.
68c, and also controls the sampling timing. Here, the number of samplings is 128 times for one scan,
A/D conversion is processed in 16 bits. The digitized image signal is stored in a lookup table composed of ROM, etc.
The image data is converted into a density value via a blueprint (LUT) 88 and stored in an image buffer 90. The LUT 88 stores a conversion table expressed by the following equation (1). Y=a×log(X+b)

...(1) Here, X is an input to the LUT 88, and Y is its output. Further, a is a constant related to conversion from photometric density determined by the spectral characteristics of imaging in the scanning unit 22 to printing density determined by the spectral sensitivity of photographic printing paper, and b is a constant related to removal of the influence of dark current in imaging. It is.

[0050] In the equation (1), LUT88 has a, b
A plurality of conversion tables are prepared by substituting several types of numerical values into , and are selected in advance by the CPU 92 . The conversion table selected here does not necessarily have to be the same for each color of B, G, and R, and may be different.

In this way, 16 pixels consisting of 128 pixels
Bits of line image density information are stored in image buffer 90 . Hereinafter, this will be referred to as primary line image density information Da.

Next, internal processing (image processing) in this image processing section 24 will be explained. The CPU 92 takes out the primary line image density information Da in synchronization with the transport pulse, performs the following rounding process, and then performs image processing in the main scanning direction to store it in the memory 94 for each scanning line.

Here, the effective line image area in the main scanning direction (first line image density information Da) may differ depending on the format of the photographic film F. So CPU9
2 sets the image area to be rounded in the main scanning direction stored in advance according to the format of the photographic film F and the number of pixels to be rounded, and each pixel in the set image area is set as the set pixel. Performs a process of rounding by number.

After processing the line image density information for a predetermined number of pixels, it is stored in the memory 94 for each scanning line. Here, the predetermined number of pixels is 16 pixels.

FIG. 5 shows an example of this embodiment. 1
35 Primary line image density information D obtained from photographic film
In a, the image area corresponding to the width of 20 mm at the center is set as the effective area, and the value 5 obtained by dividing the number of pixels corresponding to this length, 80, by the predetermined number of pixels, 16, is set as the number of pixels for rounding.

In addition, in the case of 110 photographic film, this 1
10 Primary line image density information D obtained from photographic film
In a, the image area corresponding to the width of 12 mm at the center is set as the effective area, and the value 3 obtained by dividing the number of pixels corresponding to this length, 48, by the predetermined number of pixels, 16, is set as the number of pixels for rounding.

The rounding process here takes the arithmetic average of the image density information, which has the effect of reducing the influence of noise contained in the image signal. however,
Rounding does not necessarily have to target all pixels in the selected image area; it is possible to perform arithmetic averaging by thinning out a certain number of pixels, or by thinning out only a predetermined number of pixels. A method that does not take this method is also effective if calculation speed is taken into account.

By the image processing in the main scanning direction as described above, secondary line image density information D consisting of a predetermined number of pixels, here 16 pixels, is obtained regardless of the format of the photographic film F.
b is obtained, and this secondary line image density information Db is stored in the memory 9.
4 is stored as line image density information corresponding to a large number of scanning lines as the photographic film F is conveyed.

Furthermore, the CPU 92 takes out these secondary line image density information Db stored in the memory 94,
The image is then shaped into two-dimensional image density information in a predetermined format through image processing in the sub-scanning direction, and sent to the information processing section 26.

Here, the original image on the photographic film and the memory 94
The problem is managing the correspondence with the secondary line image density information Db stored in . This management is performed based on notch signals. As described above, the notch 12 is provided in advance at the center of the original image, and is detected by the scanning unit 22. As a result, a notch signal corresponding to the position of the original image is sent from the scanning section 22 to the CPU 92 via the system bus 74. Upon receiving the notch signal, the CPU 92 counts the transport pulses, and when a predetermined processing start count is reached, retrieves the primary line image density information Da stored in the image buffer 90, until the predetermined number of scanning lines is reached. The above-described image processing in the main scanning direction is repeated until .

The address of the secondary line image density information Db stored in the memory 94 is stored in the memory 94 in response to the notch signal.
is stored in a predetermined area. In this way, the secondary line image density information Db is obtained from the original image G formed on the photographic film F.
are managed according to their location. However, the above correspondence functions relate to the arrangement of the CCD line sensors 68a, 68b, 68c for each of the B, G, and R colors. Therefore, the predetermined count value is selected and set from pre-stored constants according to the color.

This selection can be made using a switch (not shown) provided inside the image processing section 24. As a result, the image processing section 24 can have a common configuration for each color of B, G, and R, and its internal processing can also be made common. Furthermore, extremely high processing speed can be achieved by operating these in parallel.

The effective image area in the sub-scanning direction (number of scanning lines) may differ depending on the format of the photographic film F. Therefore, the CPU 92 sets the number of scanning lines stored in advance according to the format of the photographic film F as the predetermined number of scanning lines. The scanning unit 22 performs scanning once every 0.25 mm.
For example, the number of scanning lines corresponding to a processing target area of 32 mm for a full-size original of 135 photographic film is 128, but the number of scanning lines corresponding to a processing target area of 16 mm for a half-size original is 64. Therefore, the CPU 92 sets the number of scanning lines stored in advance according to the format of the photographic film F as the predetermined number of scanning lines. Furthermore, rounding processing is performed in the sub-scanning direction according to the set number of scanning lines to process two-dimensional image density information consisting of a predetermined number of pixels in the sub-scanning direction. Here, the number of pixels in the predetermined sub-scanning direction is 16. FIG. 6 shows an example of this aspect.

In the figure, for the secondary line image density information Db obtained from a full-size original image, the number of scanning lines is 12.
The value 8 obtained by dividing 8 by the predetermined number of sub-scanning pixels, 16, is set as the number of scanning lines for rounding. Furthermore, for the secondary line image density information Db obtained from the half-size original image,
The number 4 obtained by dividing the number of scanning lines, 64, by the predetermined number of sub-scanning pixels, 16, is set as the rounding number of scanning lines.

The rounding process here is to take the arithmetic average of the image density information in the sub-scanning direction, and as with the image processing in the main-scanning direction, this is used to reduce the influence of noise contained in the image signal. It is effective. However, rounding does not necessarily mean that all the stored secondary line image density information Db
There is no need to target the data, and methods that take an arithmetic average after performing appropriate thinning, or methods that only thin out a predetermined number of scanning lines and do not take an arithmetic average are also effective when considering calculation speed. It is.

Note that image processing in the main scanning direction does not need to be performed in response to all transport pulses, and may be performed intermittently. This reduces the load not only on image processing in the main scanning direction but also on image processing in the sub-scanning direction, so that the processing speed can be significantly improved. in this case,
The period of intermittent processing may be changed depending on the format of the photographic film F.

Through the above-described image processing in the sub-scanning direction, two-dimensional image density information consisting of a predetermined number of pixels, here 16×16 pixels, is finally obtained, regardless of the format of the photographic film F. This information is sent to the information processing section 26. Therefore, the information processing section 26 can perform common processing regardless of the format of the photographic film F.

FIG. 7 shows the detailed configuration of this information processing section 26.

B, G, R supplied from the image processing section 24
The two-dimensional image density information regarding each color is sent to the system bus 74.
The data is stored in the memory 102 via the . The CPU 104 reads out the two-dimensional image density information stored in the memory 102 and calculates the amount of correction for each original image G formed on the photographic film F.

This correction amount is transmitted to the exposure control section 30 through the communication line 2.
8. In addition, the conveyance control circuit 7 of the scanning section
2 via the system bus 74;
Splice signals and barcode signals are also stored in memory 102 and processed by CPU 104.

[0071] The auxiliary storage unit 106 stores information to be saved, constants necessary for processing, and the like. Note that the auxiliary storage unit 106
For example, it is a magnetic disk, and the recorded information can be taken out to the outside as necessary. This allows information to be saved even if the power is cut off, so not only can the information be stored for a long period of time, but also the saved information can be processed by an external, independent device, and constants etc. can be initialized. It can also be changed.

Further, a display 112 and a keyboard 108 are provided for operation, and an interface circuit 110
It is now possible to perform input and output via the .

Next, internal processing in the information processing section 26 will be explained.

FIGS. 8 and 9 show flowcharts of this internal processing.

First, a variable L indicating the number of original images processed in step 1 is initialized.

Next, in step 2, B, G, R
The two-dimensional image density information regarding each color is extracted, and the variable
Set to K(i,j). Here, i is the pixel position in the main scanning direction, j is the pixel position in the sub-scanning direction, K is B, G,
Each color of R is shown.

In step 3, neutral color two-dimensional image density information D(i
, j) is calculated using the following equation (2). D(i,j) = {XB(i,j)+
XG(i,j)+XR(i,j)}/3
...(2) In step 4, the characteristic value D'(m,n) is calculated for each region using D(i,j). Here m
For example, the upper position, lower position of the two-dimensional density image information,
Corresponds to the right position, left position, center position, and entire area. Further, n corresponds to, for example, the maximum value, minimum value, and average value in each region.

In step 5, the characteristic value D'(m,n)
The density correction value D''L for each original image is calculated using the following formula (3
) is determined by a linear equation as shown in Here, α(m,n) is a predetermined coefficient, and β is a constant.

In step 6, a histogram FK(s) of two-dimensional image density information regarding each color of B, G, and R is calculated. Here, s represents the image density, and K represents each color of B, G, and R.

FIG. 10 shows an example of the histogram obtained in step 6. In this figure, the horizontal axis shows the image density s, and the vertical axis shows the frequency f.

Furthermore, in step 7, the cumulative density function CDFKL(s) of the two-dimensional image density information regarding each color of B, G, and R of this original image is determined from the above histogram by the following formula (
4). FIG. 11 shows an example of the cumulative density function obtained in this way. In this figure, the horizontal axis shows the image density s, and the vertical axis shows the cumulative frequency CDF. As is clear from equation (4) and the figure, this function is continuous for any s,
and is a monotonically increasing function.

In step 8, 1 is added to a variable L indicating the number of processed original images to prepare for processing the next original image.

[0083] In step 9, it is evaluated whether this L is larger than a predetermined number N of original images, and if it is large (Yes), the next step 11 is executed, and if it is not large (No), the process in step 10 is executed again. be done. Here, the predetermined number N of original images is a predetermined constant, and this constant is related to the transport path between the scanning section 22 and the exposure section 32 in FIG. 2 described above. In this example, the maximum length of the transport path is equivalent to 135 photographic films taken with 24 images, and if the predetermined number N of original images is, for example, 24, then 1 photographic film taken with 24 images is taken.
The above-mentioned cumulative density function can be determined prior to exposure from the image density information corresponding to almost all the original images recorded on a single film of No. 35 photographic film.

Furthermore, even when there are a large number of original images, such as a 36-shot 135 photographic film F, the cumulative density function can be calculated from image density information corresponding to a sufficient number of original images to obtain statistics. It can also be determined prior to exposure.

In step 10, it is determined whether the processed original image is the last original image G recorded on one photographic film F, and if it is the last original image, the next step 1 is performed.
1 is executed, and if the answer is No, it is not the last original image, the processes from step 2 onwards are executed again. Note that the information processing section 26 has a splice signal sent from the transport control circuit 72 of the scanning section 22 via the system bus 74, which is stored in the memory 102 and processed by the CPU 104. 1 by referring to
It can be identified that this is the last original image G recorded on the photographic film (F) of the book. As a result, even when the number of original images is small, such as a 12-shot 135-photo film, the above cumulative density function can be used for exposure based on the image density information corresponding to all the original images G recorded on one of the photographic films F. can be requested in advance.

In the subsequent step 11 of FIG. 9, from the cumulative density function of the two-dimensional image density information corresponding to each original image,
Cumulative density function CDF of two-dimensional image density information regarding each color of B, G, and R of multiple original images recorded on photographic film F
MK(s) is obtained by the following equation (5) for all s. In this way, the cumulative density function CDFKt(s
) is continuous for any s and is a monotonically increasing function, so as is clear from equation (5), the cumulative density function CDFMK(s) shown on the left side is continuous for any s. , and is a monotonically increasing function.

Furthermore, the cumulative density functions can be added very easily in this way. As above, 1
A predetermined statistic, a cumulative density function CDFMK(s), is determined from a plurality of original images recorded on the photographic film F of a book.

Cumulative density function CD obtained in this way
It has been confirmed through experiments that FMK(s) has a close correlation with the tone reproduction characteristics of photographic film F.

FIG. 12 shows characteristic curves of two types of color negative films.

In the characteristic curve of one of the color negative films indicated by a broken line in the figure, only the characteristic related to the density of G tends to be soft, and the characteristics related to the density of B and R are the same. The cumulative density function related to the G density component obtained from 24 original images of the same subject photographed under the same conditions using these color negative films will be explained.

FIG. 13 shows the cumulative density function regarding the concentration component of G.

In the figure, the horizontal axis is the image density s, and the vertical axis is its cumulative frequency. Here, the maximum value of the cumulative frequency CDFM is 256 pixels (16×16
pixel) and the number of original images (24), 6344. Moreover, the broken line here is the cumulative density function obtained from the color negative film for which the broken line characteristic curve shown in FIG. 10 is shown. It is clear from the figure that a steeply curved cumulative density function is obtained from a color negative film that tends to have a soft tone.

From this, the image density of each color that gives a predetermined value to this cumulative density function is extremely effective in estimating the neutral color recorded on this photographic film F, and is used as a color in determining the photographic printing exposure amount. It can be used as a standard for correction.

Further, in step 12, an inverse function value CK is obtained from the cumulative density function for each color of B, G, and R corresponding to each original image using the following equation (6). CK = CDF-1 KL( γ
) (K = B, G, R) …(6
) Here, γ is a predetermined constant, but it is a numerical value that does not exceed 256 pixels of two-dimensional image density information, for example, 12
It is 8. In this way, the characteristic value of each original image is obtained, but this characteristic value is not limited to this example, and may be the average value of the two-dimensional image density information of each color.

The cumulative density function obtained from the two-dimensional image density information corresponding to a plurality of original images recorded on the photographic film as described above is a statistic corresponding to the tone reproduction characteristics of the photographic film F, and this cumulative density The image density of each color that gives a predetermined value to the function is extremely effective in estimating the neutral color recorded on this photographic film F, and can be used as a reference for color correction in determining the photographic printing exposure amount.

Therefore, in step 13, using the above characteristic values and the cumulative density functions obtained from a plurality of original images, C'K of the density information of each color of B, G, and R, which serves as the reference for color correction, is calculated using the following formula: It is calculated by (7). C'K = CDFMK -1(C
DFM (CG) (K = B, G, R)...(7) Note that the cumulative density function is continuous at any point and is a monotonically increasing function, so the inverse function can be found very easily in this way. It also has the advantage of not requiring exception handling due to the nature of the function.

Next, in step 14, the color correction value C''KL for each original image is determined for each color of B, G, and R using the following equation (8) using the above-mentioned characteristic values and reference density information for color correction. C"KL = C'K - CK
(K = B, G, R) …(
8) Here, C'K is the estimated value of the neutral color recorded on this photographic film, so the absolute value of C''KL is:
It takes a small value when the subject recorded in the original image has a neutral color, and takes a large value when the color distribution of the subject is uneven. Therefore, by using this color correction value, it is possible to selectively correct color feria.

Furthermore, since the average reflectance for each color of most objects is constant, the absolute value of this correction value is generally extremely small compared to the change in exposure amount based on the average transmission density of the original image. It is true. Therefore, the two-dimensional image density information for obtaining this correction value does not require high accuracy, and therefore, inexpensive elements such as CCD line sensors 68a, 68b, and 68c are used as the imaging system for scanning the original image. Furthermore, in step 15, as in step 10, the processed original image is
It is again identified whether it is the last original image recorded on the photographic film F of the book, and if the answer is Yes, it is the last original image, the process ends, and if the answer is No, it is not the last original image, then the process from step 2 onwards. is executed again.

[0099] In the above, a method for obtaining color correction values based on the tone reproduction characteristics of one photographic film F has been shown, but as described above, the system bus 74 can be The type of photographic film F is identified by the barcode signal sent via the barcode signal, and based on the result of this identification, the above cumulative density function is applied to a plurality of photographic films ( F) can be accumulated across. In this case, a plurality of cumulative density functions obtained from a plurality of photographic films (F) may be added. Due to the nature of the cumulative density function, this processing is extremely easy. By storing this result in the auxiliary storage unit 106 that constitutes the information processing unit 26, it is possible to accumulate it over a long period of time. In this way, when using the accumulated cumulative density function auxiliary, the cumulative density function CDFM''K(
s) and the cumulative density function C used in step 13.
It may be replaced with DFMK(s). CDFM”K(s)=CDFMK(s
)+α×CDFM'K(s)

(K = B, G, R) ... (9) where CDFMK(s) is the cumulative density function obtained from the original image G formed on the photographic film F to be processed, and CDFMK(s) is the cumulative density function obtained from the original image G formed on the photographic film F to be processed.
FM'K(s) is the cumulative density function accumulated as described above, and α is the weighting coefficient. Note that if the cumulative density function obtained from the photographic film F to be processed is determined from a sufficient number of cumulative density functions, for example, 24 pieces of two-dimensional image density information, a small value is given to the weighting coefficient α. The function is set as a function of the number of two-dimensional image density information so that a large numerical value is given when it is determined from a sufficient number of pieces of two-dimensional image density information, for example, four pieces of two-dimensional image density information.

[0100] As a result, adjustments are made to the process for determining the color correction value in accordance with the certainty of estimating the neutral color recorded on the photographic film F.

In this way, by using the accumulated cumulative density function as an auxiliary, it is possible to solve cases where the number of original images formed on the photographic film F is too small to obtain sufficient statistics, or when the number of original images formed on the photographic film F is too small. Even if the original image to be photographed has a particular subject extremely biased, appropriate color correction values can be determined based on the tone reproduction characteristics of the photographic film F.

[0102] In order to specify or classify the type of photographic film F based on the type identification, the information processing unit 2 prepares a correspondence table between the barcode signal and the identification code or classification code in advance.
6 in the memory 102 or auxiliary storage unit 106,
This can be done by referring to this correspondence table. The classification here refers to photographic film F with similar characteristics.
It is desirable to assign the same code to both.

Density correction value D” obtained as above
L and the color correction value C"KL are sent to the exposure control section 30 through the communication line 2.
8 and is used to determine the photographic printing exposure.

Next, the determination of the photographic printing exposure amount in the exposure control section 30 will be explained.

The photographic printing exposure amount is determined according to the following equation (10). EK = LATDK - LATD
0K +α×C”KL+β

×D'L +E0K (10) Here, EK is the exposure amount (logarithm value of exposure time) of each color of B, G, and R, and LATDK is the printing caused by the photodiodes 44a, 44b, and 44c in the exposure section 32. Average transmission photometric value (logarithm) from the original image submitted to LATD0
K is the average transmitted light photometric value (logarithm) from the standard original image, C”K
L is the color correction value sent from the information processing section 26, α is a coefficient for adjusting the intensity of color correction, D'L is the density correction value sent from the information processing section 26, and β is the intensity of the density correction. The coefficient for adjustment, E0K, is the exposure amount (logarithm value of exposure time) set for the standard original image, K is each color of B, G, and R, and L is the processing order of the original image.

Therefore, the exposure amount is determined based on the average transmitted light photometric value of the original image, and is corrected by the color correction value determined in consideration of the tone reproduction characteristics of the photographic film F. Here, the average transmitted light of the original image is photometered at the time of exposure. Therefore, it is possible to detect variations in illumination light in the exposure system and changes in density due to image deterioration during exposure, and thereby adjust the exposure amount, thereby significantly reducing these effects. Therefore, in the end, it is possible to obtain an optimum exposure amount that takes into account the tone reproduction characteristics of the photographic film F, the characteristics of each original image, and various fluctuations during exposure. Also, B
, G, and R, a photometric element with a large light-receiving area can be used to measure the average transmitted light of the original image for each color. As a result, a sufficient dynamic range can be obtained through sufficient photometry, and the density of the image G formed on the photographic film F, which can be recorded over a wide density range, can be measured accurately and stably. The exposure amount for the original photograph can be determined with reproducibility.

Furthermore, since this photometry is performed independently in the exposure stage, there is no need to go through the scanning stage again when reprinting. In this case, the density correction value and color correction value used in the first printing can be recorded, for example, on the back side of the photographic print, and when reprinting, corrections corresponding to these correction values can be input to the exposure control section 30. , a photographic print equivalent to the photographic print obtained at the time of initial printing is obtained, and reprinting can be easily performed by inputting the necessary corrections.

[0108]

As explained above, according to the method for determining the photographic printing exposure of the present invention, the correction amount for the photographic printing exposure is determined mainly according to the tone reproduction characteristics of the photographic film. By setting exposure conditions for each type of photographic film in advance, it is possible to properly determine the exposure amount in photographic printing without having to change the exposure conditions set according to the type of photographic film to be printed. It is possible to stably and efficiently produce photographic prints of a constant quality even when the tone reproduction characteristics deteriorate due to.

[0109] The exposure amount is determined based on the average transmission density of the original image, and this exposure amount is corrected by the above-mentioned correction amount, so even if the original photographic image is scanned using a simple and inexpensive imaging system, the photographic image can be taken with high reproducibility. It is possible to determine the exposure amount for the original image, and at the same time it is possible to stably produce photographic prints of a constant quality even against fluctuations in illumination light in the exposure system and image deterioration during exposure. can be reheated.

Furthermore, according to the present invention, it is only necessary to additionally connect a scanning device to a conventional photographic printer having the function of measuring the average transmission density and determining the exposure amount, thereby minimizing the economic burden. Not only can the process be greatly improved, but the functions of conventional photo printing equipment can also be continued as they are.

In addition, according to the present invention, the type of photographic film is identified by reading the barcode attached to the photographic film, and based on the result of this identification, it is classified into a specific type or into a predetermined classification. Statistics based on the tone reproduction characteristics of photographic film are calculated for each type of film. An appropriate amount of correction can be determined even when the number of original images is small and sufficient statistics cannot be obtained, or when the original images on the photographic film are extremely biased toward a specific subject.

[0112] Therefore, it is possible to stably produce photographic prints of a constant quality regardless of variations in the characteristics of photographic film or an increase in the variety of photographic films, and regardless of simultaneous printing, reprinting, or reprinting. Great effects can be obtained in promoting the wide-ranging rationalization and efficiency of treatment processes.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a 135 photographic film used to explain the method for determining the photographic printing exposure amount of the present invention.

FIG. 2 is a schematic diagram showing the general configuration of a photographic printing apparatus to which the photographic printing exposure determining method of the present invention is applied.

FIG. 3 is a configuration diagram showing details of the scanning section in FIG. 2;

FIG. 4 is a configuration diagram showing details of the image processing section in FIGS. 2 and 3;

FIG. 5 is a diagram illustrating a part of image processing in the main scanning direction for explaining the embodiment.

FIG. 6 is a diagram illustrating a part of image processing in the sub-scanning direction for explaining the embodiment.

FIG. 7 is a configuration diagram showing details of the image processing section in FIGS. 2 and 3;

FIG. 8 is a flowchart showing internal processing in the information processing section.

FIG. 9 is a flowchart showing internal processing in the information processing unit following FIG. 8;

FIG. 10 is a diagram showing an example of a histogram used to explain the embodiment.

FIG. 11 is a diagram showing an example of a cumulative density function used to explain an example.

FIG. 12 is a characteristic diagram showing characteristic curves of two types of color negative films provided for explanation of Examples.

FIG. 13 is a diagram showing a cumulative density function regarding the concentration component of G, which is used to explain an example.

[Explanation of symbols]

20 Spool 22 Scanning section 24 Image processing section 26 Information processing department 28 Communication line 30 Exposure control section 32 Exposure section 34 Buffer section 38 Diffusion part 40 Photographic paper F Photographic film

Claims (8)

[Claims] Claim 1. In a photographic printing exposure determination method, in which the average transmission density of an original image formed on a photographic film is measured and the exposure amount for the original image is determined based on this density, the photographic film is A plurality of original images formed in the original image are scanned, a predetermined statistic is obtained from the image information of the plurality of original images obtained thereby, an image characteristic value is calculated from the image information of each original image, and then a statistic value is calculated from the image information of each original image. A photographic printing exposure determining method characterized in that a correction amount is determined from the image characteristic value and the image characteristic value, and the exposure amount is corrected based on the correction amount. 2. The photographic printing exposure amount determining method according to claim 1, wherein the predetermined statistic is a cumulative density function of image information of a plurality of original images. 3. The photographic printing exposure amount determining method according to claim 1, wherein the characteristic value is an average value of image information of each original image. 4. Claim 1, wherein the characteristic value is an inverse function of a cumulative density function of image information of each original image.
Described method for determining photographic printing exposure. 5. The photographic printing exposure amount determining method according to claim 1, wherein the plurality of original images are original images spanning a plurality of photographic films. 6. The photographic printing exposure amount determining method according to claim 5, wherein the plurality of original images are original images spanning a plurality of photographic films belonging to a specific type. 7. The photographic printing exposure amount determining method according to claim 5, wherein the plurality of original images are original images spanning a plurality of photographic films belonging to a predetermined classification. 8. The photographic printing exposure amount determining method according to claim 6, wherein the type is identified by reading a bar code attached to the photographic film.