JPH03153232A - Method for photographic printing - Google Patents

Abstract

PURPOSE:To reflect the intention of composition upon a print without deteriorating the finish quality of the print by varying the degree of correction of image density, where unbalanced coloration occurs in color reproduction according to variation in the color temperature of subject illumination light, according to the intention of composition. CONSTITUTION:When the color temperature of the subject illumination light varies, the color taste reproduced in the print varies on a broken line L. Therefore, the degree of correction of image density on the broken line L or image density in a specific range (e.g. hatched area R1 or R2) including the broken line L, i.e. image density where unbalanced coloration is caused in the color reproduction according to the variation in the color temperature of the subject illumination light is varied according to the intention of composition to represent the color taste corresponding to the color temperature of the subject illumination light on the print. Consequently, the photographer's intention of composition can be reflected without deteriorating the finish quality.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photographic printing method, and particularly to a photographic method in which the amount of printing light is automatically determined based on the image density of the film image and the film image is printed on photographic paper. Regarding the printing method.

[Problems to be solved by the prior art and the invention] B (
It is known from experience that the transmission ratio of three color lights (blue), G (green), and R (red) is generally a substantially constant ratio. Printing conditions are determined so that the color obtained by integrating and mixing the densities printed on color photographic paper by transmitted light over the entire screen becomes gray or a constant hue close to gray. Therefore, in an automatic printer, the amount of printing light (W light amount) may be determined based on the following equation.

ji! ogEj=Kj+Dj...(1) However, lo
gE is the logarithm of the amount of printing light, K is a constant, D is the negative integrated transmission density (LATD) measured with a photometric system, and j is any of B, G, and H color light.

However, if the amount of printing light is controlled by the automatic printer based on equation (1) above, prints from underexposed negatives of gray subjects will have a higher overall density than prints from properly exposed negatives, and Prints from excessive negatives will be less dense. Therefore, the exposure amount is determined by correcting Dj in equation (1) using the slope control function. On the other hand, even with automatic printers equipped with the slope control function described above, negatives shot under light sources that are significantly different from daylight (fluorescent lamps, tungsten lamps, etc.) (different light source negatives), and color area With certain negatives, color reproduction tends to be polarized, resulting in defective prints with incorrect color balance.

For this reason, the exposure amount is determined by further correcting (color correction) Di in equation (1). At this time,! 11m
An excessive correction is called a high correction, and an undercorrection is called a lower correction.

By automatically correcting the printing exposure amount as described above, it corrects the polarization of color reproduction caused by different light source negatives and fluctuations in film characteristics (performance fluctuations due to film storage, performance fluctuations due to processing variations, etc.) This allows you to efficiently create prints with good quality.

However, the photo printing method described above assumes a uniform print finish, and therefore cannot reflect the photographer's artistic intentions.For example, a sunset scene may be converted to a midday scene. There is a problem. In order to solve this problem, it is possible to determine the exposure amount using a lower correction, but since it is not possible to correct the polarization of color reproduction due to fluctuations in film characteristics, the finished quality of the print deteriorates.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photographic printing method that can reflect the photographer's drawing intention without deteriorating the finished quality.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a photographic printing method in which a film image is printed on photographic paper by correcting the printing light amount determined based on the image density of the film image. The present invention is characterized in that the degree of correction of image density at which polarization occurs in color reproduction is changed according to the intention of drawing.

In the present invention, the light source color information used to estimate the color temperature of the object illumination light is recorded on the film as necessary at the time of shooting, and the presence or absence of the light source color information is detected at the time of printing to determine the drawing intention. good.

[Effect]

The present invention will be explained in detail below. When the color temperature of the object illumination light changes, the color tone reproduced on the print changes along the broken line in FIG. 2. FIG. 2 shows color coordinates represented by RlG, B, Y (yellow), C' (cyan), and M (magenta) axes.

Therefore, in a photographic printing method in which a film image is printed on photographic paper by correcting the printing exposure amount determined based on the image density of the film image, the image density above the broken line in FIG. 2 or a predetermined range including this broken line is The image density within (for example, the shaded area R1 or R2 in FIG. 2), that is, the degree of correction of the image density at which polarization occurs in color reproduction according to changes in the color temperature of the object illumination light, is adjusted according to the drawing intention. By changing this, it is possible to express on the print a color tone that corresponds to the color temperature of the illumination light of the subject, and therefore it is possible to express the photographer's drawing intention. Note that, at this time, image density correction that does not cause polarization in color reproduction in response to changes in the color temperature of the object illumination light is performed in the same manner as in the past.

In addition, when photographing a subject illuminated by low color temperature light such as a sunset, tungsten light, winter sun, morning sun, or lamp light, the degree of correction may be weaker because the photographer's intention is often reflected. Often, when a photograph is taken under high color temperature light such as on a cloudy day, before sunrise, or in the shade, it is necessary to strongly correct the image in order to obtain a good finished print. For this reason, if the intention of the drawing is to be reflected in the print, the light source color information used to estimate the color temperature of the subject illumination light is recorded on the film, and if the intention of the drawing is not to be reflected, the light source information is not recorded on the film. In other words, the light source color information may be recorded as necessary, and the presence or absence of the light source color information may be detected to determine the drawing intention.

〔Effect of the invention〕

As explained above, according to the present invention, the degree of correction of the image density at which polarization occurs in color reproduction is changed in accordance with the drawing intention in accordance with changes in the color temperature of the object illumination light, and other image densities are Since the degree of correction is not changed, the effect is that the drawing intention can be reflected in the print without degrading the print finish quality.

〔Example〕

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

In this embodiment, the present invention is applied to a color photo printing apparatus (printer). As shown in FIG. 3, a mirror box 18 and a lamp house 10 equipped with a halogen lamp are arranged below the negative carrier 12 that conveys the negative film 20 to the printing section. mirror box 1
A light control filter 60 is arranged between the lamp house 10 and the lamp house 10 . As is well known, the light control filter 60 is
(yellow) filter, M (magenta) filter and C
It consists of three color filters: (cyan) filter.

Above the negative carrier 12, a lens 22, a black shutter 24, and a color paper 26 are arranged in this order, and the light from the lamp house 10 illuminates the dimmer filter 60.
, the light beams transmitted through the mirror box 18 and the negative film 20 are imaged onto the color paper 26 by the lens 22.

A two-dimensional image sensor 3 that divides a negative image into a large number of parts and measures the image density of the negative film 20 in a direction oblique to the optical axis of the imaging optical system and at a position where the image density of the negative film 20 can be measured.
0 is placed.

As shown in FIG. 4, on the negative film 20, drawing information 34 indicating the intention of drawing is recorded, as well as photographing time information 36 indicating the timing of photographing. Drawing information 3
4 is sufficient as long as it is information that can at least confirm whether or not a correction change to the exposure amount is necessary, and information that does not require a correction change may be recorded, but it is used for estimating the color temperature of the subject illumination light, which will be described later. It is also used as shooting information 36, LV value (EV value) information, light source color information, etc., and when any of these information exists, it is necessary to correct the exposure amount, that is, to reflect the drawing intention. It may be determined that Also,
The photographing time information 36 uses the photographing date (the year may be added) and the photographing time, and this photographing information is printed at the time of photographing using the date and time imprinting mechanism of the camera.

In FIG. 4, the information at the time of photographing is displayed numerically, but it may be recorded with a bar code, or an optical mark displayed with a light emitting diode or the like may be used. Furthermore, the position where information is recorded on the film is not limited to the position shown in FIG. It may be recorded in the department.

On the upstream side of the negative carrier 12, at a position where the information recorded on the film can be read, there are a first sensor 14 that optically reads drawing information 34, and a second sensor that optically reads shooting information 36. 16 are arranged. The first sensor 14, the J2 sensor 16, and the two-dimensional image sensor 30 are a control circuit 2 composed of a microcomputer.
8 is connected. A keyboard 32 is connected to the control circuit 28 for inputting data and the like. Also,
The control circuit 28 is connected to control the dimming filter 60.

Next, the burn-in control routine by the microcomputer of this embodiment will be explained.

FIG. 1 shows the printing processing routine of this embodiment. In step 100, drawing information detected by the first sensor 14 is read. In step 102, it is determined based on the drawing information whether or not the drawing intention is to be reflected in the print, that is, whether there is a correction change. When there is no need to change the correction, that is, when printing is performed using only the automatic correction function of the printer, in step 104, the exposure control value Ej is calculated based on, for example, the following equation (2). Then, in step 112, printing is performed by controlling the light control filter 60 based on the exposure control value Ej.

1ogEj=Sj (Cj (dj-dwj) +dwj) 10Kj...(2) However, dj=Dj-NDj...(3) where j: represents either R, G, or H Any number from 1 to 3 Dj: Image density of film image frames to be printed (e.g., average density of all screens) NDj: Average image density of standard negative film or a large number of film frames (e.g., average density of all screens) Sj Nislope control value CJ: Color correction value Kj: Constant depending on printer, film, and photographic paper characteristics Ej: Exposure control value corresponding to the amount of printing light.

When it is determined in step 102 that a correction change is necessary,
That is, when the drawing intention is reflected in the print, the color temperature of the object illumination light is estimated in step 106. A detailed routine for estimating the color temperature will be described later.

In the next step 108, based on the estimated color temperature, a color correction value Cj of an image density whose color tone changes with a change in the color temperature of the object illumination light is set. When the estimated color temperature is below a predetermined value, that is, when the subject is illuminated with low color temperature light (for example, sunset, tungsten light, etc.), the correction by the color correction value Cj is weak. Or it is set to a value that causes no correction. In other words, it is set to be burned in the lower collection.

For example, when the color correction value Cj is set to 1.5, color field correction is performed, but light source color correction is not performed, and tungsten light is reproduced with a strong YR taste. In addition, in the case of a weak high correction, for example, when the color correction value Cj = 1.3, color area correction is not performed and only light source color correction is performed, and when the subject illumination light is tungsten light, the tungsten color is It will remain. As described above, by making the correction based on the color correction value weak or not making any correction, the color of the object illumination light is reflected in the print, and it is possible to create a print according to the drawing intention. The correction is set to be stronger when the estimated color temperature is high color temperature light (for example, cloudy weather, shade, etc.). For example, if the color correction value Cj is set to 2.0, only the light source correction is performed in the same way as above, and tungsten light is printed in daylight color.

At this time, the image density does not change depending on the color temperature of the object illumination light (image density other than the shaded area in Figure 2).
The color correction Cj of is set to the same value as in step 104.

゛Then, in step 110, the exposure control value Ej is calculated based on the above equation (2), and in step 11
Execute the burn in step 2.

In FIG. 5, the vector A is the color correction value C
It indicates the degree to which the image density including the color of the object illumination light contributes to the exposure control value when j is small (for example, 0.5), and the vector A' has a color correction value slightly larger than 1 (for example, , 1.3), and vector A'' indicates the contribution of the image density to the exposure control value when the color correction value is large (for example, 2.0). This indicates the size of the contribution to

As can be understood from the figure, as the color correction value increases, the image density is corrected to become closer to the average image density ab.

Next, a color temperature estimation method will be explained. First, the first estimation method will be explained with reference to FIGS. 6 and 7. In this case, a position outside the screen corresponding to the subject photographing screen of the film is exposed with subject illumination light at an amount equal to the subject exposure amount or an exposure amount at a fixed ratio to the subject exposure amount to provide light source color information.

The exposed position may be the drawing information recording position. Figure 7 shows the exposure amount density (light source color density) L due to object illumination light outside the screen.
The difference between Dj and average image density NDJ is shown in relation to color j. As can be understood from Fig. 7, the relationship between color difference LDj - NDj and image density is a straight line B with a positive slope when the color temperature of the object illumination light is low, and a negative slope when the color temperature is high. When the color temperature is standard, it becomes a straight line C parallel to the j-axis. Further, when the object illumination light is fluorescent lamp light, the curve A is upwardly convex. Therefore, in the color temperature estimation routine shown in FIG. 6, in step 120 the light source color density LDJ, average image density NDj1 image density is taken in, and in step 122 the data taken in represents the straight line B-C. It is determined by calculation whether the curve A or the curve A is shown. In the next step 124, it is determined whether the determination result indicates a straight line,
If it is not a straight line, that is, if it is a curve, step 12
In step 6, the light quality is determined to be fluorescent light and is stored in a predetermined area of the RAM.

If it is determined in step 124 that the slope is a straight line, steps 128 and 132 determine whether the slope is positive, negative, or 0.
If the slope is positive, low color temperature light (for example, light with a color temperature of 4500 degrees or less) is determined in step 130, and if the slope is negative, high color temperature light (for example, light) is determined in step 136. , light with a color temperature of 6000° or more), and if the slope is 0, in step 134 standard light (
For example, light having a color temperature of 4,500 to 6,000 degrees is determined and stored in a predetermined area of the RAM.

The second color temperature estimation method is a method using image average densities R, G, and B. As shown in FIG. 8, if the color difference RG is the horizontal axis and the color difference GB is the vertical axis, the region P existing in the first quadrant is the region where the color difference of low color temperature light exists, and the third quadrant The region Q existing in is a region where color difference of high color temperature light exists.

Therefore, the difference in average image density GB, RG is the area P, Q
By determining which of these belongs, it is possible to determine whether the color temperature of the object illumination light is high or low, that is, the light quality of the object illumination light.

Next, a third method of color temperature estimation will be explained.

This method uses information at the time of photographing, that is, the date and time of photographing. When using this method, the sunrise time SQ, sunset time SI, and time until the sun becomes high X for each month and day of the region where the printer is installed are set in accordance with the season. For example, this time X is 1 in the summer, 3 in the winter, and 1 in the southern region.
, is set to 3 in the northern part. The color temperature estimation routine will be explained with reference to FIG. In step 140, the photographing time information 36 is fetched to fetch the photographing date and time T, and in step 142, the sunrise time SQ, sunset time SI, and time X corresponding to the photographing date are fetched. In step 144, the photographing time T is compared with the time SQ+X at which time X has elapsed since sunrise, and in step 146
, shooting time T and time 5l X hours before sunset.
-Compare with X. When SQ + to estimate color temperature.

When T<SQ+X, in steps 152 and 154, the photographing time T and the time 5 one hour before sunrise are
Q-1,0, time 5Q-0, 0.5 hours before sunrise.
Compare with 5. When T<5Q-1,0, it is determined that it is nighttime and the process proceeds to step 150. Also, 5Q-1,0≦T<
When 5Q-0, 5, it is 30 minutes to 1 hour before sunrise, so it is determined in step 158 that the color temperature is high, that is, the object illumination light is high color temperature light. Also SQ+X
When <T:i; 5Q-0.5, it is the time from 30 minutes before sunrise until the sun becomes high, so it is determined in step 156 that the color temperature is low, that is, the subject illumination light is low color temperature light. .

When T>5I-X, 0.0 from sunset as above.
Time SI+0.5, which is 5 hours after sunset, time SI+1.0, which is 1 hour after sunset, and photographing time T are compared. If the photographing time T has exceeded 1.0 hour after sunset, it is determined that it is nighttime and the process proceeds to step 150, and the color temperature is high at times from 0.5 hours to 1 hour after sunset ( Step 1
Proceed to step 66, and if 5I-X<T:1m5I+0.5 (7), it is determined that the color temperature is low (low color temperature light) and step 1
The process advances to 64 and stores each color temperature in RAM.

Next, a fourth method of estimating color temperature will be explained.

This method uses the LV value (EV value), that is, the light intensity value at the time of shooting. Usually, low color temperature light is not bright;
The small V value is used to distinguish between a yellow background and low color temperature light.

In step 170, it is determined whether the LV value is greater than or equal to a predetermined value,
When the LV value is greater than or equal to a predetermined value, it is determined that the color temperature is high (high color temperature light), and the light is stored in the RAM in step 172. Furthermore, when the LV value is less than a predetermined value, the color temperature is estimated using the other method described above.

By combining the second method and the fourth method, or by combining the second, third, and fourth methods, it is possible to accurately estimate whether the light is tungsten light or fluorescent light.

In addition, although the example in which information indicating the drawing intention, information at the time of shooting, etc. is recorded on the film has been described above, it is also possible to attach a magnetic recording section connected to the film or a storage means such as a magnetic card, an IC card, or a C to the film. The information may be stored in the storage means of the lever.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the printing processing routine of an embodiment of the present invention, Fig. 2 is a diagram showing the direction of polarization of color reproduction caused by variations in the color temperature of the illumination light of the object, and Fig. 3 is a diagram to which the present invention is applied. A schematic diagram of a possible color automatic printing device; Figure 4 is a plan view of a film that stores drawing information, shooting information, etc.; Figure 5 is for explaining the degree of contribution of image data when changing color correction values. FIG. 6 is a flowchart showing the routine of the first method of estimating color temperature, FIG. 7 is a diagram for explaining this first method, and FIG. FIG. 9 is a flowchart showing the routine of the third method of estimating color temperature, and FIG. 10 is a flowchart showing the routine of the fourth method of estimating color temperature. 20... Negative film, 26... Photographic paper, 30... Image sensor.

Claims (2)

[Claims] (1) In a photographic printing method that prints a film image onto photographic paper by correcting the printing light amount determined based on the image density of the film image, polarization occurs in color reproduction depending on changes in the color temperature of the subject illumination light. A photo printing method characterized by changing the degree of image density correction according to the intention of drawing. (2) In a photographic printing method that prints a film image onto photographic paper by correcting the printing light amount determined based on the image density of the film image, light source color information used to estimate the color temperature of the object illumination light is required at the time of shooting. It records on the film according to the image, detects the presence or absence of light source color information at the time of printing, determines the intention of the image, and adjusts the degree of image density correction that causes polarization in color reproduction according to changes in the color temperature of the subject illumination light. A photo printing method characterized by changing the image according to the intention of the image.