Photographic printing method and equipment for setting light- source-saturation correction by using presumptive light source detection

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a photographic system capable of detecting a background light source (scene illuminant) and the use of the system for performing saturation correction in a photographic print process.

【0002】

[Conventional technology]

Traditionally, photographic background color balance algorithms used in automated printers use film density (R, G, B) measurements and related mathematical techniques that are applied on a background-by-background basis to expose the film to photographic paper. I was trying to get the optimum level of saturation correction from the film. Causes of color changes in film images that require a high level of saturation correction (eg, non-daylight illuminants, effects of film processing, effects of film storage and manufacturing changes) and high levels. If the printer cannot identify the difference from the cause of the color change in the film image that does not require saturation correction (for example, a very colorful subject in the background), the background color-guided printer correction It is said that failures (failures) occur. Therefore, it is desirable to recognize and separate color sources according to the level of saturation correction required.

【0003】

The background light source is one of the most typical causes of color change in film images. Being able to recognize the type of background light source and input this information into the printer algorithm can help you choose the right level of saturation correction and apply it. In the cameras described in US Pat. Nos. 4,827,119 and 5,037,198, the background of natural light, tungsten light, fluorescence, etc. is obtained by Fourier series analysis of one or more harmonics of the light source signal obtained from the camera's optical sensor. Can detect and identify various typical light sources in. This identification data can be recorded at the time of photography and sent to a photofinishing printer for application to the exposure determination algorithm processing. The transfer process for recording such data optically records the data as a latent image on the film, and the magnetic data is recorded or programmable on a magnetic layer formed on the film or a separable magnetic medium. It is electronically stored in a simple memory medium (EEPROM).

【0004】

[Problems to be Solved by the Invention]

The use of the special light source detection and identification device as described above has some effect for that purpose, but is disadvantageous in that it increases the cost and complicates the camera design. Moreover, such systems are based on the detection of known harmonic frequencies and are therefore limited to existing background sources. Therefore, new detection devices are required for new light sources that generate different harmonic frequencies, and current cameras cannot cope with them, making them obsolete. It ends up. The increased cost of the camera by performing a Fourier series-based analysis makes it unusable in low-cost cameras, so when making improved saturation corrections in the print process, such The light source correction technique cannot be easily used.

【0005】

US Pat. No. 5,016,039 describes a camera for detecting and recording specific background light source information, which is read by a photographic printer to control the exposure of the film image to photographic paper. And used. The retrieved information includes light level, flash emission and subject distance to determine the color temperature of the background light source. Complex analyzes are performed to accurately identify different color temperatures associated with daylight and to identify different non-daylight sources. According to the patent, in low light level (non-daylight) backgrounds, if the subject distance exceeds the point where the flash is effective, it accurately determines the background light source color temperature to be sent to the photographic printer after recording. To use a color temperature meter. However, there is no mention of how the recorded and transmitted information is used in the photo printer algorithm. In addition, the equipment disclosed in this patent requires complex calculations to accurately identify various background light sources and light levels in order to record accurate color temperature information. Also background shooting space (scene) A color temperature meter must be used to identify the light source in the entire area of photospace). In all of these respects, it is not intended to increase the cost and complexity of the camera device and to provide simplified algorithmic operations as an exposure technique in photographic printers.

【0006】

U.S. Pat. No. 5,168,303 describes a device for determining control of a photographic printer's algorithm from data recorded during photography. This patent provides many methods for determining the color temperature of a background light source with its printer from data such as light value, flash emission, shooting date and time, and geographical location where the shooting was taken. Will be disclosed. This information is the background in the print (other than the removal of the green cast caused by the fluorescent light source, which is an additional step that requires complex light source detection and / or algorithmic manipulation). It is used to control the printer exposure algorithm to automatically superimpose the density-based exposure determinants, including saturation correction, to preserve the color cast of the light source. The effect provided by this patent is contrary to the object of the present invention, that is, the present invention provides an easy way to remove the color cast produced by a non-daylight background light source from a printed image. It is a thing.

【0007】

Therefore, an object of the present invention is to provide a simplified photographic system for detecting and identifying a background light source, which helps to set an appropriate level of saturation correction in a photographic printing process.

【0008】

Another object of the present invention is to achieve proper saturation correction in a photographic printer by a simplified estimation of background light sources without the need for complex identification for many different levels and types of background light sources. Is.

【0009】

A further object of the present invention is to use data obtained from current conventional sensor devices typically provided in cameras to simplify light source detection and identification for controlling saturation correction algorithms in automatic printers. Is to provide.

【0010】

[Means and Actions for Solving Problems]

According to the first aspect of the present invention, a photographic printing method for exposing a film frame image on photographic paper in which a constant light source saturation correction is set by using information recorded in a camera obtained from shooting data. provide. According to this method, the recorded information is detected by a photographic printer, and from the detected information, an index regarding the background light level and the presence / absence of a predetermined amount of flash light source in the film frame image are determined, and the index is used. , (A) Background light level above a predetermined value, or (b) Background light level below a predetermined value, and when the predetermined amount of background light source is present in the film frame image, daylight When a low light source saturation correction corresponding to the correction is set, and the index is at a background light level below the predetermined value, and the predetermined amount of flash light source is not present in the film frame image. Is to set a high degree of light source saturation correction corresponding to non-daylight correction.

【0011】

[Example]

In the drawing, FIG. 1 shows a camera 10 that includes a film feed mechanism 12 for supporting and feeding the silver halide film 14. The lens 16, the aperture mechanism 20, and the shutter mechanism 22 are arranged so as to control the exposure of the frame to the film 14. For example, the controller 18 made of a microprocessor is connected to the aperture mechanism 20, the shutter mechanism 22, and the film feed mechanism 12. The electronic flash unit 24 is connected to a controller 18 that communicates charging and operating state data with the electronic flash unit 24, and a shutter mechanism 22 that operates by receiving a light emitting signal. The shutter release button 25 is connected to the controller 18, and by its operation, the controller 18 sets the aperture 20 and drives the shutter 22. The camera is also connected to a controller and includes an autofocus unit 27 that measures the distance between the camera and the subject and focuses the lens 16 in the usual way.

【0012】

The camera 10 further includes an optical level sensor 26 and a recording device 28, both of which are connected to the controller 18. The light level sensor 26 is selected and arranged to sense the background light level and can be configured with a normal automatic exposure sensor used to calculate the exposure of an image on film 14. The light level sensor 26 also has a returned flash illumination in the background taken for the purposes described below. ) Is used to detect. The recording device 28 is preferably composed of a magnetic recording head that magnetically encodes data with a magnetic recording layer formed on the surface of the film 14. In the present invention, such a recording mechanism is preferable, but other well-known recording techniques such as an optical and mechanical recording method or a magnetic recording method performed on a removable magnetic medium such as a disk or an integrated circuit card are used. It can also be used. As described in US Pat. No. 5,229,810, a variety of data is recorded by the camera, the description of which is referred to here. However, special data relating to the present invention, namely those relating to the background light level and those relating to the presence or absence of a predetermined amount of flash light source in the exposed background, will be described in detail below.

【0013】

FIG. 2 shows a photographic printer conforming to the present invention. In the illustrated printer, the rolled processed photographic film 30 is fed from the supply reel 32 to the take-up reel 38 via the exposure determination film scanner 34 and the photographic printing department 36 by a feeding means (not shown). .. Even if the feed rate of the film changes temporarily between the film scanner 34 and the photographic printing department 36, a cushioning unit 40 of the film loop may be provided so as to cope with the change.

【0014】

The exposure determination film scanner 34 typically includes a light source 42 for transmitting light to the film frame image on the film 30 arranged at the scanner frame gate 44. The formed image light corresponds to a scanning image sensor 46 that can be configured as a charge-coupled device (CCD) in a linear or two-dimensional array. U.S. Pat. No. 5,153,715, granted October 6, 1992, provides a virtual contact scanner useful as an exposure determination film scanner 34. ) Is described, but here it is referred to. The output of the scanning image sensor 46 is supplied to the AD converter (analog-digital data processing processor) 48 in the form of an analog signal of the scanned pixels, and the analog pixel information received from the scanning image sensor 46 is input by a well-known method. Converted to a digital value to represent. This digital data is then supplied to the exposure determination computer 50, which operates to determine the correction film exposure value for performing regular optical printing in the printing department 36 by a well-known method. In order to read the data magnetically recorded by the camera, a data sensor 51 preferably composed of a magnetic reading head is provided. The detected data is converted into digital data by the A / D converter 48 and sent to the exposure determination computer 50.

【0015】

The printing department 36 usually includes an optical printer light source 52, a color filter 54, a light collecting box 56, a film gate 58, an image optics 60 and a print gate 62. Photographic paper 64 of a certain length is fed from the supply reel 66 to the hoisting reel 68 through the printing department 36 in synchronization with the film 30 by a suitable feeding means (not shown). The image of the film 30 is continuously exposed on the photographic paper 64 while being controlled by a signal from the exposure determination computer 50 in order to set desired exposure conditions for printing the film frame.

【0016】

As is well known, in photographic printing of color images using automatic printing technology that uses computer algorithms to determine the spectral characteristics of film image exposure to photographic paper, the exposure of the original film image in the camera underneath. The color accuracy of the printed image can be improved by segregating the image according to the type of light source performed and setting the saturation correction based on that distinction. US Pat. No. 4,827,119 discloses a technique that can separate the light source that exposes a film image into several main light sources: daylight, tansugten, and fluorescence. When applying the exposure deterministic algorithm, multiple subject failure suppression (SFS) boundaries based on the light source are useful to give a special color balance offset for each of these light source types. Is also known.

【0017】

The present invention provides improved printer color for all light sources, whether daylight or non-daylight, using a method that is simpler and cheaper to implement than the specific light source identification methods described above. It provides a correction. With a high level of saturation correction, the exposure made to a daylight-balanced film is the final representation (eg, print) from a background illuminated by any type of non-daylight-balanced light source. The unexpected fact that it is done most accurately in is an important feature of this new method. This eliminates the need for separately preset color balance positions for each different light source type. In other words, when any non-daylight source (eg, tungsten, fluorescence or halogen) is used to expose the background on the film balanced in daylight, it is typical of the scanned color density recording of the film. Differences from background density recordings balanced in daylight will be processed with a high level of saturation correction. That is, the density difference in the exposed film image is substantially caused by the change in the light source (with respect to daylight) and is completely eliminated.

【0018】

Modern automatic optical printers, such as the Kodak Model 3510 Color Printer or the Kodak CLAS35 Color Printer, are designed to provide 100% saturation correction as needed. The level of saturation correction is typically suppressed by the SFS boundary and is the subject color that is part of the scanned density recording of the film image when taken under daylight or daylight balanced flash. Make a more moderate level of correction to avoid overcompensation for subject-matter color failures. However, when the non-daylight source is recognized by the putative light source detection according to the method of the present invention, a high level of saturation correction can be effectively applied to remove the unwanted color cast that degrades the image quality.

【0019】

According to the features of the present invention, the following background-specific quantities recorded on the camera during the exposure of each film frame image are useful for estimating the light source detection.

【0020】

Background light level (SLL) Camera-subject distance (D) Flash emission signal Flash reflection signal These are easily to establish the criteria for determining whether there is daylight-balanced lighting (DL) or non-daylight-balanced lighting (NDL) in the background shot on the film frame. A particular combination of the resulting amounts can be used. Once the light source is presumably determined from this data when balanced in daylight or non-daylight, the automatic printer algorithm provides an appropriate level of light source saturation correction.

【0021】

Exposures made to daylight-balanced film from a background illuminated by any type of non-daylight-balanced light source are final when high levels of saturation correction are applied. As a result of the unplanned fact that it is most accurate in the representation (eg print), there are two light sources rather than separate classifications for each light source (eg tungsten, fluorescence, mercury, halogen). The color image quality formed by the automatic printer can be significantly improved by a method that can be separated into classes (daylight and non-daylight). A background sensor based on a normal camera can be used to easily and efficiently separate the light sources into these two classes, resulting in an putative light source detection and printer control method. .. In FIG. 3, region 1 is a region representing daylight and covers all camera-subject distances from close range to long range for all light levels above a predetermined level Y. Level Y usually corresponds to the level at which the camera fires the flash, although in some cases it is slightly different. This area is the area of photographic space typically characterized by natural daylight illumination. Therefore, when the background light level (SLL) is in this region, the exposure determination computer 50 applies daylight saturation correction. This generally corresponds to low or weak levels of saturation correction. The light level Y is calculated by the following formula in foot tram belt (unit).

【0022】

Y = KA²N / ST Here, K = ANSI exposure constant (typically 3.91) A = f-number of camera lens S = ISO film sensitivity N = desired exposure bais (1.0 = standard exposure, 0.5 = -1 aperture, 0.25 = -2 aperture) Typically, in a camera exposure control system, 0.5 and 0.5 to activate the flash system when the ambient lighting is not at a level sufficient to produce a normal exposure to the film loaded in the camera. It is set to N between 1.0.

【0023】

In the graph of FIG. 3, the area 2 representing flash / no flash is generally below the background light level Y at which the flash operates, over the maximum distance X at which the flash is effective, or an equivalent distance between the camera and the subject. There is. This area is characterized by the presence of daylight-balanced flash illumination in the shooting background. Therefore, the daylight saturation correction is appropriate for the background image taken in this region where the flash that actually emits light is provided. The fact that the flash has fired is displayed by recording the flash flash signal with the camera, and the signal is sent from the shutter to the flash unit 24 (Fig. 1). The maximum flashable distance X is calculated in feet by the following formula:

【0024】

X = GN / AN Here, GN = flash guide number for a particular ISO film sensitivity and distance scale A = f-number of camera lens S = ISO film sensitivity N = desired exposure bias (1.0 = standard exposure, 0.5 = -1 aperture, 0.25 = -2 aperture) It can be known by recording the subject distance based on the autofocus reading that the subject distance is equal to or less than the maximum effective distance X of the flash. If the distance is less than or equal to X and the flash emission is recorded, the daylight saturation correction is applied by the photographic print exposure algorithm. Another approach to determining if a subject is in area 2 of the photographic space is by ascertaining and recording the presence of a given flash reflected light as perceived by the camera's light meter. This operation is described in detail in the international application which is the subject of International Publication WO-89 / 09964, and the description shall be referred to here.

【0025】

As mentioned above, region 2 is typically characterized by daylight balanced flash illumination and daylight saturation correction for images taken within this region in the presence of a flash light source in the film image. Is appropriate. However, in the absence of a flash, the lighting is just artificial, as determined by the method described above. As a result, non-daylight saturation correction is applied to the image captured in this region by the exposure determination computer.

【0026】

Area 3 representing non-daylight covers a limited photographic space area where the camera-subject distance is greater than or equal to the maximum flash-effective distance X and the background light level is less than or equal to the calculated light level Y. ing. This area is characterized by non-daylight balanced artificial lighting. Therefore, for images captured in this region, non-daylight saturation correction, which preferably corresponds to 100% high level saturation correction, is appropriate. In region 2, the light level is determined by data from the sensor 26, and "distance X and above" is determined by either data representing flash emission or flash reflected light at the subject distance.

【0027】

Since an object of the present invention is to improve the color image quality formed by the automatic printer algorithm by applying an appropriate level of saturation correction in the printing process, the idea using the above criteria is in the camera. Can also be done in a photo printer. When performed on the camera, the saturation correction command is recorded on the film by the camera and sent directly to the exposure determination computer. Also, if done in a printer, raw photographic data about the background light level that the subject was within the flash range (as a flash emission signal and subject distance or flash reflection signal) is recorded in the camera. , Sent to the exposure determination computer for the appropriate determination of the saturation correction command.

【0028】

As is clear from the above description, a method of effectively using the putative light source detection to improve the color image quality formed by the automatic optical printer by a simple method has been described. It is clear to those skilled in the art that this method of invention can be used to improve the color image quality formed by other displays or reproduction means such as photo CD video displays, thermal printers, CRT displays and printers and electrophotographic printers. Is.

【0029】

The present invention has been described in detail herein with particular reference to preferred embodiments. The use of other standard or non-standard methods of indicating background light levels and effective flash distances will be apparent to those of skill in the art. Therefore, it is understood that the modification or modification is effective within the scope of the present invention described in the claims.

【0030】

[Effect of the invention]

As described above, according to the present invention, by effectively using the presumptive light source detection, the color image quality formed by the automatic printer algorithm is improved by applying an appropriate level of saturation correction in the printing process. can do.

[Simple explanation of drawings]

[Figure 1]

It is the schematic of the photographic camera configured for recording the photography data useful for this invention.

[Figure 2]

FIG. 6 is a schematic diagram of a photographic printer configured to use data recorded on a camera according to the novel features of the present invention.

[Fig. 3]

It is a graph which shows the background brightness and the subject distance for demonstrating the principle of this invention.

[Explanation of symbols]

10 camera 12 Film feed mechanism 14 film 16 lenses 18 controller 20 Aperture mechanism 22 Shutter mechanism 24 Electronic flash unit 26 Optical level sensor 28 Recording device 30 photographic film 32 supply reel 34 Exposure decision film scanner 36 Photo print department 38 take-up reel 40 Film loop buffer 42 light source 44 Scanner Frame Gate 46 Scanned image sensor 48 A / D converter 50 Exposure determination computer 51 Data sensor 52 Optical printer light source 54 color filter 56 Luminous box 58 film gate 60 Image optics 62 Film gate 64 photographic paper