JP2592013B2 - Exposure control method and exposure control device for plate making camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control method for performing halftone photographing with a plate making camera and an exposure control apparatus for implementing the method.

[0002]

2. Description of the Related Art When performing halftone photographing with a plate making camera, one of methods for controlling the contrast of a halftone negative image corresponding to various originals is an auxiliary exposure method. This method generally uses a negative contact screen to expose the main exposure, highlight exposure without a screen to increase the contrast from the light to the middle of the document, and soften the contrast from the dark to the middle of the document. Therefore, a method of obtaining a net negative image corresponding to the contrast of the original by appropriately combining the main exposure, the highlight exposure and the flash exposure, comprising flash exposure for giving uniform exposure to the entire film using the screen. is there. Regarding the exposure control technology for implementing the auxiliary exposure method, conventionally, for example, a printing magazine (1.
August 975 issue. VOL. 58, pages 43 to 47
Page 35) and “35 Years of Imaging Technology” (issued on October 11, 1978,
(Pages 93 to 99) are known.

[0003] For example, as shown in FIG. 7, it is provided with a half-tone photographing data setting input unit 121 capable of setting and inputting basic data and original data, and an exposure control unit 125 having a built-in exposure calculating unit 127. Based on the basic data and the original data, the main exposure amount T _M , the highlight exposure amount T _H , and the flash exposure amount _TF are calculated to control the exposure of the plate making camera. The photographing magnification m of the plate making camera is taken into the exposure calculation unit 127 via the automatic focus control unit 130, and the lens aperture F _NO and the line drawing basic data T ₀ are also taken into the exposure calculation unit 127. Exposure calculation is appropriately performed.

The basic data includes main exposure basic data, highlight basic data, and flash basic data. For example, as shown in FIGS. 6 and 7, the main exposure basic data is a basic main exposure time T. and _BM, which contains the basic main exposure time T _BM highlight halftone dot area ratio a _H in the case of the net shooting, the reference image density B _MIN0, B _MAX0 respectively corresponding to the shadow area coverage a _S. In general, A _H =
The desired values are 95% and A _S = 5%. (B _MAX0
-B _MIN0 ) is the density area B where the contact screen can be duplicated
_DR . On the other hand, the highlight basic data is obtained by _performing halftone photographing with the basic highlight exposure time T _BH and the basic main exposure time T _BM , and then giving the highlight exposure without a screen for the basic highlight exposure time T _BH , The reference original image density B _MIN1 corresponding to the highlight halftone dot area ratio A _H at this time is included. On the other hand, the flash basic data is obtained by taking a halftone image with the basic flash exposure time T _BF and the basic main exposure time T _BM , giving the flash exposure for the basic flash exposure time T _BF , it includes reference original density B _MAX1 corresponding to a _S. The original data includes a highlight density D _MIN and a shadow density D _MAX from which a highlight halftone dot area ratio _AH and a shadow halftone dot area ratio _AS are to be obtained as a result of halftone photographing, respectively, and (D _MAX −D _MIN )
Is the density range _DDR of the original.

[0005] The basic data and the manuscript data are network photographing data.
Is input to the data setting input unit 121 and the exposure calculation unit 127
Based on the following formulas (1) to (4),
Time T_M, Flash exposure time T_FOr highlight exposure
Time T_HIs calculated and the required exposure control is executed.
Is configured. (B) If the density range of the original is larger than the density range of the screen
(D_DR> B_DR) T_M= T_BM・ 10^A … (1) where A = D_MIN-B_MIN0  T_F= T_BF× {1-10^-C｝ / {1-10^-F…… (2) where C = D_DR-B_DR  F = B_MAX1-B_MAX0  (B) The density range of the original is smaller than the density range of the screen
Case (D_DR<B_DR) T_M= T_BM・ 10^B … (3) where B = D_MAX-B_MAX0  T_H= T_BH・ 10^D・ {(1-10^C) / (1-10^-E)}… (4) where D = D_MIN-B_MIN1  E = B_MIN1-B_MIN0  Note that, in actuality, the photographing magnification m and the lens
Aperture F_NOIs corrected.

[0006]

In general, it can be said that the above-mentioned exposure control method has no theoretical problem under strict exposure and development control. However, in practice, the sensitivity of the photosensitive material varies depending on the production lot. As for the development process, there is some variation in the activity of the developer at each time, and it may be difficult to accurately measure the highlight density and shadow density of the original data. And the desired halftone dot area ratio A _{H in} the highlight corresponding portion and the shadow corresponding portion of the halftone film obtained by shooting
Or _AS may not be obtained.

In such a case, in the above-mentioned conventional example, the original data D _MIN or D _MAX is corrected and halftone photographing is repeated again. However, the correction of the original data D _MIN and D _MAX is performed in the previous network. It must be predicted from the result of the photographing, and it is difficult for an operator without considerable experience. or,
The correction of the manuscript data had to be changed by judging whether the photographic material used was a negative type or a positive type. The present invention has been made in consideration of such circumstances, and does not use a dot density as in the related art, and makes a desired dot area ratio A _H , in retaking again when a _S is not obtained, the operator directly original data D _MAX, has no requirement to modify the D _MIN, and substantially desired to highlight the corresponding portion and the shadow corresponding portion by retaking It is a technical task to obtain a dot area ratio.

[0008]

The present invention is configured as follows to solve the above-mentioned problems. That is, the first invention controls the exposure by calculating the main exposure amount, the highlight exposure amount, and the flash exposure amount based on the main exposure basic data, the highlight exposure basic data, the flash exposure basic data, and the original data, respectively. The exposure control method for a plate making camera according to the above, wherein the halftone dot image obtained by photographing based on each of the basic data and the original data has a dot area ratio of a highlight corresponding portion and a shadow corresponding portion with respect to a desired value. The shortage amount is defined as a result halftone correction value, and the main exposure amount and the high exposure amount are determined by using the highlight halftone correction data and / or the shadow part correction data included in the basic data. A method of correcting at least one of a light exposure amount and a flash exposure amount to obtain a desired halftone dot in a highlight corresponding portion and a shadow corresponding portion. That.

A second invention is an exposure control device for a plate-making camera comprising a half-tone photographing data setting input section and an exposure control section having a built-in exposure calculating section. A basic data setting input section in which data for highlight section correction and data for shadow section correction are set in addition to the exposure basic data, highlight exposure basic data, and flash exposure basic data, an original data setting input section, and a desired high When the light dot area ratio and the shadow dot area ratio cannot be obtained, the result is an excess / deficiency amount with respect to a desired value.
A correction data setting input unit in which a correction value is set, and using the highlight part correction data and / or the shadow part correction data, the main exposure amount and the highlight are obtained through the halftone correction value. An exposure control device of a plate-making camera for correcting at least one of an exposure amount and a flash exposure amount.

[0010]

In the exposure control method and apparatus according to the present invention, if the desired highlight halftone dot area ratio _AH or shadow halftone dot area ratio _AS is not obtained in the halftone dot image, the halftone dot area ratio is obtained. Is used as the correction value as it is with respect to the desired value. As a result, the dot% correction value can be easily obtained by measuring the dot area ratio of the highlight corresponding portion and the shadow corresponding portion of the dot image with a dot meter or the like. Then, at the time of re-taking, at least one of the main exposure amount, the highlight exposure amount, and the flash exposure amount is corrected via the halftone% correction value. Therefore, it is not necessary for the operator to make a difficult determination of predicting the correction value of the document data from the result of the previous halftone photographing. As a result, a desired halftone dot can be obtained without the operator correcting the original data or the basic data.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an exposure control device according to the present invention,
FIG. 2 is an external perspective view of a vertical plate making camera provided with the exposure control device. First, the vertical plate making camera will be briefly described. As shown in FIG. 2, the vertical plate-making camera is provided with a photographing rack 3 provided on an upper opening frame 2 of a substantially U-shaped base frame 1, and a lens rack 10 and a document rack 15 provided so as to be vertically movable. It is configured to be doubleable. The above-mentioned shooting rack 3
Is rotatably hinged to the focus glass 4 on the right side of the upper opening frame 2 and the film suction plate 5 to the left side, and selectively rotates the focus glass 4 and the film suction plate 5 to form an image. It is configured to be positioned on a surface. An operation panel 6 incorporating an exposure control device (reference numeral 20 in FIG. 1) according to the present invention is provided on the front side of the photographing rack 3, and original data and a dot area ratio of a dot image are measured on the right side. A densitometer 7 is additionally provided, and the densitometer 7 includes a light emitting unit 7a and
b.

The lens rack 10 is connected to the upper opening frame 2 via a bellows 8, and a plurality of imaging lenses 1 are provided at the center of the lower surface of the lens rack 10 so as to cover a required photographing magnification range.
1 is provided with a lens interchangeable, and a filter turret 1 having a plurality of color separation filters 13 in a lens mount 10.
2 and a pair of left and right flash lamps 14 are provided. The document table 15 is provided with a document table 16 provided to be able to move up and down, a document pressing glass plate 17, and a light source arm 18 on the document table 16.
A pair of reflective illumination light sources 19 supported via a light source, and a transmissive illumination light source (not shown) mounted on the lower side of the document table 16. The camera is configured so that it can be set at a desired magnification together with the lens mount 10 and photographed via an automatic focusing mechanism (reference numerals 30 to 32 in FIG. 1).

Hereinafter, an exposure control apparatus according to the present invention will be described. As shown in FIG. 1, the exposure control device 20 includes a net image data setting input unit 21 capable of setting and inputting various data from the operation panel 6, and an exposure control unit 25. That is, in the present invention, the halftone data setting input unit 21 includes a correction data input unit 24 for inputting correction data in addition to the basic data input unit 22 and the original data input unit 23. The basic data input to the basic data input unit 22 includes the same main exposure basic data (T _BM , B
_MIN0, B _MAX0), highlight exposure basic data (T _BH, B
_MIN1 ), flash exposure data (T _BF , B _MAX1 )
For example, highlight part correction data as shown in FIG.
_{(A H, A H1, B} MIN2, B MIN3) and shadow correction data _{(A S, A S1, B} MAX2) and feeling material type positive type or negative type of data is added input. These basic data are used by the exposure calculation unit 27 to correct the main exposure amount, the highlight exposure amount, and the flash exposure amount. As the correction data set and input to the correction data input unit 24, the amount of excess or deficiency with respect to a desired value when a desired highlight halftone dot area ratio _AH or a shadow halftone dot area ratio _AS is not obtained is obtained as a result. The correction values ± δ _H and ± δ _S (%) are used. Here [delta] _H corresponds to a highlight portion of the original results networks% correction value, [delta] _S is the result networks% correction value corresponding to the shadow portion of the original. This is because a person involved in the plate making operation easily recognizes the expression using the dot area ratio and suits the actual situation of the plate making operation.

First, the case where the photosensitive material is a negative type will be described. The exposure calculation unit 27, in order to obtain the desired screen to highlight the corresponding portion and the shadow corresponding section, the result net% correction value ± [delta] _H, the original data D _MIN based on the ± [delta] _S,
D _MAX is further corrected by equations (5) and (6). D _MIN1 = D _MIN ± K _H · δ _H (5) D _MAX1 = D _MAX ± K _S · δ _S (6) Here, as shown in FIG. In addition to the dot area ratios A _H and A _S of
Somewhat smaller A _H1 than _H, somewhat greater A than A _S
A dot area ratio of _S1 is set, and a standard original image density (B) at a position where a line drawn with these dot area ratios crosses each gradation characteristic curve
_{MIN0, B MIN1, B MIN2,} B MIN3 and B _MAX0, B _MAX1,
B _MAX2 ), the coefficients K _H and K _S for converting the resultant halftone _dot correction value into the density correction amount can be determined as follows. First, the correction coefficient K _{H of the} highlight part
Can be calculated by the following equation using the gradation characteristic curve by the main exposure (T _BM ) when D _DR > B _DR . K _H = (B _MIN2 −B _MIN0 ) / (A _H1 −A _H ) (7) In the case of D _DR ≦ B _DR , gradation selection by main exposure (T _BM ) + highlight exposure (T _BH ) Using the curve, it can be calculated by the following equation. K _H = (B _MIN3 −B _MIN1 ) / (A _H1 −A _H ) (8) Next, the correction coefficient K _S of the shadow portion can be calculated by the following equation using the gradation selection curve by the main exposure. . K _S = (B _MAX0 -B _MAX2 ) / (A _S -A _S1 )} (9)

Since these correction coefficients K _H and K _S are determined by the type of the contact screen irrespective of the sensitivity of the photosensitive material and the activity of the developer, they are set as basic data for each contact screen used. What is necessary is just to obtain from the calculated value by calculation. Where D _DR <8
Since the correction coefficient K _{H in} the case of B _DR depends on the ratio between the basic main exposure time (T _BM ) and the basic highlight exposure time (T _BH ), one type of main exposure time (T _BM ) is set in advance. , Set the highlight exposure time (T _BH ) in several steps, and determine the density range from each gradation characteristic curve.
(B _MAX0 -B _MIN1 ) and K _H are obtained, and the density range D _{DR of the} document is obtained.
It is more accurate exposure management when to use the K _H corresponding to nearest said density range in. The correction coefficient K
_{Since H} and K _S involve the complexity of additionally inputting the basic data for correction of the highlight part and the shadow part in addition to the basic data of the conventional example, the equations (7) to (9) are used. It has been confirmed that there is no practical problem if a predetermined value (constant) is used instead of calculating each time. Also in this case, K _H is several to have a predetermined value as described above, they are better to the selectively used in accordance with the D _DR can more accurate exposure control.

Regarding the main exposure amount and the highlight exposure amount, D _MIN1 and D _MAX1 obtained by the equations (5) and (6) are _calculated by D
_MIN, instead of _{D MAX (1), (3} ), can be corrected simply by substituting the equation (4). But about flash exposure (2)
The formula needs to be reviewed. That is, in equation (2), (5)
It is D _DR = C in C that is modified and changed by equation (6).
_MAX− D _MIN , and a change of this amount cannot obtain a desired halftone dot area ratio in the shadow corresponding portion. There is a difference in the sensitivity of the photosensitive material and the development activity of the automatic developing machine between the time when the basic data was obtained and the current time, and these effects influenced the desired halftone dot area ratio in the shadow corresponding part according to the basic data. If not, it is necessary to correct the basic flash exposure time T _BF itself, and it is necessary to introduce the following equation (10) instead of the equation (2). T _F = T _BF · 10 ^{± Kδ} (1-10 ^-C )
/ (1-10 ^-F ) (where Kδ = K _S δ _S ) (10) T _BF · 10 ^± K δ in this equation can be said to be a corrected basic flash exposure time, and δ _S = When 0, equation (10) matches equation (2). In this equation, C and F are expressed by equation (2), and K _S is expressed by
This is the same as equation (9), and the difference between D _MAX1 and D _MIN1 is applied to D _DR in the equation C = D _DR -B _DR . In the present invention, since each exposure amount is corrected based on the gradation characteristic curve, not only the fluctuation of the photosensitive material sensitivity and the development activity but also the density measurement or setting error of the original data can be corrected. In the case of a relatively small width, for example, if the error is within ± 5 to 10% of a desired halftone dot, a sufficiently effective correction is performed.

Next, the case where the photosensitive material is a positive type will be described. FIG. 5 shows each basic data and gradation characteristic curve in the case of the positive type. As can be seen by comparing FIG. 5 with FIG.
_H, determines the _{K S (7) (8)} (9) magnitude relationship photosensitive material A _H and A _H1 and A _S and A _S1 of formula is reversed depending on whether a negative type or positive type, K _H, the K _S The sign is reversed. Therefore,
Even if the setting is somewhat complicated, if K _H and K _S are calculated each time using the equations (7), (8) and (9), appropriate correction can be performed without paying attention to the positive or negative. On the other hand, when the setting is considered complicated, and K _H and K _S are directly set at predetermined values,
Instead of inverting these values and resetting them, look at which setting of the photosensitive material type is used, and in the case of the positive type, change the signs of K _H and K _{S in} the exposure calculation unit 27. What is necessary is just to invert and calculate. Note that the absolute values of K _H and K _S are almost determined by the contact screen used, and the signs are simply reversed depending on whether the photographic material used is positive or negative. Further, actually the correction with respect to a change in imaging magnification m and the lens aperture F _NO in these equations have been added.

FIG. 3 is a flowchart showing an example of a procedure of screen photographing in the plate making camera. Hereinafter, the procedure of the net photographing will be described. In step S _1, is set all Enter basic data in advance the. In step S _2,
An original is loaded on an original frame 15 of a plate making camera, a photosensitive material is placed on a film suction plate 5, and a contact screen is closely adhered thereon and held by suction, and then the film suction plate is rotated to form an image forming surface. Position. Step S original data from the operation panel 6, ₃ (D _MIN, D _MAX) sets enter and photographing magnification m. In step S _4, the automatic focusing mechanism (30, 31, 32)
Is operated to move the lens rack 10 and the document rack 15 to the required magnification position. In step S _5, the calculation of the main exposure time in the exposure control unit 27 T _M and the flash exposure time T _F or highlight exposure time T _H is made, the result is the step S ₆
Is displayed on the display section of the operation panel. Step When you start the in S ₇ main exposure original illumination lamp 19 is mainly exposed lit by a required time is performed. From Step S ₈ in the calculation result, determines one Do need flash exposure or highlight exposure, perform the flash exposure in step S ₉ if required flash exposure, if the highlight exposure is required, after removal of the contact screen in step S _10, executes the highlight exposure in step S _11. This completes the net photography once.

[0019] Step S ₁₂ in the sensitive material is developed,
The measured results area coverage at a concentration meter 7 and rated the finish, determines the necessity of correction in step S _13. Here, the densitometer 7 can also measure the halftone dot area ratio. If the correction is not necessary, the halftone photographing of the original is completed. If necessary the correction, in accordance with the excess or deficiency amount results halftone dot area ratio in the correction data input unit 24 in step S _14, the correction value ± δ _H, ± δ _S set inputs (%). Even if the photosensitive material is of the positive type, ± δ _H and ± δ _S may be set and input in accordance with the excess or deficiency of the dot area ratio as in the negative type. Step S according to _15, the correction value, by the equation (5) (6), the original data D _MIN, along with D _MAX is modified D _MIN1, D _MAX1 respectively, a review of the basic flash exposure time Done. Then, the process returns to step S _5, the calculation of the exposure time by the original data D _MIN1, D _MAX1 was fixed is made, the network shooting is performed in step S ₇ to S _11. In the above embodiment, the exposure control device is described as being built in the vertical plate-making camera.However, the present invention is not limited to this. The exposure control device is manufactured as an independent exposure control device and connected to various types of plate-making cameras. Can also be used.

[0020]

As is apparent from the above description, in the present invention, when a desired highlight dot area ratio _AH or shadow dot area ratio _AS is not obtained in a halftone dot image, the resulting halftone dot area ratio is determined. The excess / deficiency of the dot area ratio is used as a correction value as it is, and as a result, the main exposure, highlight exposure, and flash exposure are corrected via the halftone correction value. It is not necessary to make a difficult decision of predicting the correction value of the document data from the result of the above and re-taking the image, and the operator does not need to directly correct the document data. In addition, almost desired halftone dots can be obtained by re-taking, which is convenient. Since the material type is set as a part of the basic data, it is not necessary to consider the material type when setting the halftone correction value.

[Brief description of the drawings]

FIG. 1 is a block diagram of an exposure control device according to the present invention.

FIG. 2 is an external perspective view of a vertical plate-making camera provided with an exposure control device according to the present invention.

FIG. 3 is a flowchart showing a procedure of halftone photographing according to the exposure control method of the present invention.

FIG. 4 is a graph schematically illustrating the concept of negative type basic data.

FIG. 5 is a graph schematically illustrating the concept of basic data of a positive type.

FIG. 6 is a graph schematically illustrating the concept of conventional negative type basic data.

FIG. 7 is a diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

_{T BM, B MIN0, B MAX0} ... main exposure basic data, T _BH, B
_MIN1 ... Highlight exposure basic data, T _BF, B _MAX1 ... flash exposure basic _{data, A H, A H1, B} MIN2, B MIN3 ...
Highlight part correction data, A _S , A _S1 , B _MAX2 ... shadow part correction data, δ _H , δ _S … result halftone dot% correction value,
T _M : main exposure, T _H : highlight exposure,
T _F : flash exposure amount, 21: halftone data setting input section, 22: basic data input section, 23: original data input section, 24: correction data input section, 25: exposure control section, 27: exposure calculation section.

Claims (2)

(57) [Claims] An exposure control is performed by calculating a main exposure amount, a highlight exposure amount, and a flash exposure amount based on main exposure basic data, highlight exposure basic data, flash exposure basic data, and original data. An exposure control method for a plate making camera, comprising: determining an excess or deficiency of a halftone dot area ratio of a highlight corresponding portion and a shadow corresponding portion of a halftone image obtained by shooting based on each of the basic data and the original data with respect to a desired value. By defining the result halftone correction value and using the highlight part correction data and / or shadow part correction data included in the basic data, the main exposure amount and the highlight exposure amount are obtained through the result halftone correction value. Exposure control for a plate-making camera, wherein at least one of the flash exposure amounts is corrected to obtain desired halftone dots in a highlight corresponding portion and a shadow corresponding portion. Method. 2. An exposure control apparatus for a plate-making camera comprising a half-tone photographing data setting input section and an exposure control section having a built-in exposure calculating section, wherein said half-tone photographing data setting input section includes main exposure basic data, high In addition to the basic data for light exposure and the basic data for flash exposure, a basic data setting input section in which data for highlight section correction and data for shadow section correction are set, an original data setting input section, and a desired highlight halftone dot area ratio And a correction data setting input unit in which a halftone correction value is set as a result of an excess or deficiency with respect to a desired value when the shadow halftone dot area ratio is not obtained, and data for highlight part correction and / or By using the shadow portion correction data, at least one of the main exposure amount, the highlight exposure amount, and the flash exposure amount is obtained through the result dot% correction value.
Exposure control device for plate making camera that corrects one.