JPS6340128A - Gamma correcting method for simulator - Google Patents

Abstract

PURPOSE:To improve the S/N ratio, and also, to generate a simulator at a low cost by executing simultaneously corrections corresponding to a gamma characteristic of a CRT and a gamma characteristic of photographic paper. CONSTITUTION:As for a usual TV system, gamma of a TV is set to about 2.2 so that a visual observation becomes satisfactory, therefore, a gamma correcting circuit of (R)=0.45 is provided on a TV camera so as to become gamma=1 as a whole, but in case of a usual print, it is finished so as to be contrasty as gamma=about 2.0. Therefore, a single gamma correcting circuit which has set gamma to about 1 (0.45X2.0) is provided in a simulator without providing a gamma correcting circuit in a camera 30, so that a correction corresponding to a gamma characteristic of a CRT and a correction corresponding to a gamma characteristic of photographic paper can be executed simultaneously. In this way, since a single gamma correcting circuit is used, the cost is reduced, and also, since gamma of the gamma correcting circuit becomes about '1', gamma is scarcely varied by the gamma correction in the simulator, and a picture quality of the CRT becomes satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gamma correction method for a simulator, and particularly to a method for printing a finished print on a CRT that is the same as a finished print that has been printed and processed on photographic paper by a color automatic photo printing device. This invention relates to a gamma correction method for a simulator to be displayed.

[Conventional technology]

Conventionally, the product of the entire image of color negative film! By measuring the i3 excess degree (LATD), correcting the density, and performing slope control, the density and color balance of all finished prints are the same regardless of whether the negative is light or dark, underexposure, proper exposure, or overexposure. An automatic color photographic printing apparatus is known that prints and develops images so that the following results are obtained. This automatic photographic printing apparatus is constructed by sequentially arranging an optical system including a light source, a light control filter, a mirror box, a negative carrier, and a black shutter. Printing is performed by placing a color negative film on a negative carrier, turning on a light source and opening a black shutter to form an image of the color negative film on the photographic paper.The printed photographic paper is then developed through a development process. The printer is configured so that the print is automatically finished. In this automatic photo printing device, the light that has passed through the negative film is detected by a light receiving element such as red light (R), green light (G), and blue light (
B) primary color separation and LATD based on Evans' theorem.
The color balance is controlled by controlling the degree 'a' and performing slope control so that the slopes are the same for the three primary colors. Therefore, according to this automatic photoprinting apparatus, all of the normally finished prints have the same degree of printing and color balance.

However, even if the main subject of a color negative film has an appropriate density, if the background is dark or light,
Since the exposure amount is controlled under the influence of this background density, a 4 degree flare occurs.

Furthermore, when the color balance of the main subject is different from the color balance of the background, for example, when the color of the main subject and the color of the background are complementary colors, a color area occurs. Therefore, even if density correction and slope control are performed, the quality of the print may deteriorate. In this way, if the finished state of the print deteriorates, it becomes necessary to carry out printing and development again.

For this reason, conventionally, as shown in Japanese Patent Application Laid-open No. 53-46731, a TV left camera negative film image is taken and the T.
A simulator that displays images on the V screen is installed,
While displaying the image, the color video signal is adjusted so as to obtain the desired color balance and color balance, and the image is printed using an automatic photo printing device using the so-called photo certification method. There is. Also,
As shown in Japanese Patent Publication No. 42-25220, there is a system in which an image of a negative film printed on photographic paper is displayed on a TV screen, and an automatic exposure machine is linked with a resistor for adjusting the brightness and contrast of the TV. In this way, images are simulated so that the frequency of reprinting and development processing is reduced.

[Problem that the invention seeks to solve]

However, since the γ of conventional TVs is approximately 2.2, the camera is equipped with γ-0.45 to compensate for the TV's γ.
A γ correction circuit is provided so that γ becomes 1 as a whole. On the other hand, in order to improve the appearance of prints, γ-
2,0 tends to produce a high contrast finish, so corrections are made in the simulator that correspond to the γ characteristics of photographic paper.
, 0, it was necessary to provide a γ correction circuit. For this reason, the r (about 0.6) of color negative film is reduced by the camera's γ correction circuit, and further increased by the γ correction circuit in the simulator, resulting in a deterioration of the S/N ratio and the TV.
There was a problem that the image quality deteriorated. In addition, since γ correction is performed in two places: the camera and the simulator,
There is a problem in that two γ correction circuits are required, which increases the cost.

The present invention has been made to solve the above-mentioned problems.
The purpose of this invention is to provide a gamma correction method for a simulator that has a good ratio and can be created at low cost.

[Means for solving problems]

In order to achieve the above object, the present invention captures an image recorded on a film, takes into account the γ characteristics of CRT and the γ characteristics of photographic paper, and transfers the same image recorded on photographic paper to CRT. In correcting γ of the simulator to be displayed, the above C
It is characterized in that corrections corresponding to the γ characteristics of RT and the γ characteristics of the photographic paper are performed simultaneously.

[Effect]

According to the present invention, correction (0,
45) and correction (2,0) corresponding to the γ characteristic of photographic paper at the same time, the γ correction circuit uses r = 1.
It is sufficient to provide one γ correction circuit of (0,45×2.O). As the conversion coefficient for γ correction, as mentioned above, it is sufficient to use a coefficient of approximately 1 once, so the simulator can adjust the negative γ
is hardly converted, and as a result, deterioration of the S/N ratio can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, the correction corresponding to the γ characteristic of the CRT and the correction corresponding to the γ characteristic of the photographic paper are performed simultaneously, and the correction of r#1 is performed only once. The effect is that the simulator can be manufactured at low cost without deteriorating the image quality.

〔Example〕

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

This embodiment combines an automatic color photo printing device (hereinafter referred to as a printer) and a device (hereinafter referred to as a simulator) that displays an image taken on a color negative film in the same state as that printed by the printer.

As shown in Figure 1, light a composed of a halogen lamp
On the back side of 10, there is a reflecting mirror 1 composed of a cold mirror.
2 is placed. The light 'a10 is supplied with a voltage of approximately 90% of the rated voltage from a power supply device (not shown) in order to prolong the life of the light #10 and obtain a predetermined color temperature. On the light irradiation side of the light source 10, there are Y (yellow) filter plates each configured by combining two fan-shaped filter plates of approximately 1/4 circle formed by a logarithmic curve and arranging them in pairs on the left and right.
A light control filter 14 consisting of three complementary color filters of M (magenta) and C (cyan) and a mirror box 16 equipped with a scattering plate are arranged in this order, and the light rays emitted from the light tA10 are colored by the light control filter 14. After the balance and light amount are adjusted, the mirror box 16 converts the light into uniform diffused light, and the diffused light is irradiated onto the color negative film 18 held on the negative carrier. In order to set the light source voltage above to 3m, set each complementary color filter of the dimmer filter to the mechanical center, measure the light intensity with a luminometer, and adjust it to a constant light intensity (standard exposure time) to achieve the rated value. Adjust so that approximately 90% of the voltage is supplied. An optical system 20 and a black shutter 22 are arranged in this order on the exit side of the transmitted light from the color negative film 1. When the black shutter 22 is opened, the light that has passed through the color negative film 18 forms an image on the photographic paper 24 to form a print. Configured to expose paper. The exposed photographic paper 24 is processed in a development process 25 to form a print 27.

A drive circuit 26 is connected to the light control filter 14, and the drive circuit 26 moves each of the complementary color filters in a direction perpendicular to the optical axis, thereby making it possible to adjust the color balance and light amount. Further, a drive circuit 29 is connected to the black shutter 22 .

Near the 20 optical systems of the color negative film 18, R
R, G is equipped with three filters that transmit red (red) light, G (green) light, and B (blue) light, respectively.

A camera 30 configured with a three-panel camera that outputs a B signal, and an image information detection device 32 that includes a two-dimensional image sensor for detecting image density information of the three primary colors R, G, and B.
is located. This two-dimensional image sensor is a CCD
(charge-coupled device). In addition, camera 3
0 may be configured with a COD single-chip camera.

Here, in a normal TV system, T of the TV is set to be about 2.2 for good visual visibility, so a γ correction circuit with γ = 0.45 is installed in the TV camera, and γ = 0.45 as a whole.
1, but in normal printing r=2
．． In this embodiment, a γ correction circuit with a T of approximately 1 (0.45×2.0) is provided in the simulator, instead of a γ correction circuit provided in the camera 30. Thus, corrections corresponding to the γ characteristics of the CRT and corrections corresponding to the γ characteristics of the photographic paper are performed at the same time.

In this way, since a single γ correction circuit is used, the cost is reduced, and since T of the γ correction circuit is approximately 1, T hardly changes due to γ correction in the simulator, and CR
The image quality of T becomes better.

The camera 30 is connected to a simulator 34 via a gain control circuit 33, and the image information detection device 32 is connected to a slope control circuit 62 via a δ and γ correction circuit 38 and a printing system density calculation circuit 40. has been done. The printing system fourth degree calculation circuit 40 and slope control circuit 62 perform the color balance and seven degree correction described above. In addition, a chromaticity meter 42 is placed opposite to the screen of the CRT 345 that constitutes the simulator 34.
is arranged, and a chromaticity meter 44 is arranged so as to face the screen of the print 27. Color meters 42, 44 are connected to the I10 boat 46 that constitutes the computer. The computer is the I10 boat 46, CP
U4 B, read-on memory (ROM) 50, random access memory (RAM) 52, digital-analog (D/A) converter 54, analog-digital (A/D)
It is configured to include i converters 56 and 58 and buses 60 such as data buses and control buses that connect these, and is connected to a gain control circuit 33, a simulator 34, a δ and γ correction circuit 38, and a printing system density calculation circuit 40. It is connected to the connected slope control circuit 62 and drive circuit 26, and is also connected to the drive circuit 29.

The gain control circuit 33 is composed of an amplifier 331, an operational amplifier 332, a flip-flop 333, and resistors 334 to 336, as shown in FIG. A reference voltage (0.7V corresponding to the white level) is input. In order to adjust the gain of the camera 30 using the gain control circuit 33, a reference negative (so-called plain negative) obtained by developing an unburnt film is imaged by the camera 30, and R, G, B,
This is done by outputting an analog signal from the D/A converter 54 for the camera output of each of the three primary colors, and stopping the gain adjustment when the signal is output from the flip-flop 333. Since the white level of the camera can be adjusted when the negative 33J light is at its maximum, the brightness standard can be determined accurately and easily.

In addition, the iris position and color balance position of the camera after the gain has been adjusted as described above can be stored as digital values, and the chances can be adjusted for each different type of negative film or negative size (the amount of light changes because the magnification is different). If you change the negative, you can change the channel by simply changing the channel.

By doing this, even if the type of negative film or negative size changes, the iris position and color balance position of the camera can be changed simply by switching channels. In the above case, if the light source deviates from the standard state, it will be necessary to electrically correct the deviation.
It is preferable to adjust the light source so that a standard gray negative produces a standard gray print.

As shown in FIG. 3, the δ and γ correction circuit 38 includes a signal processing circuit 60 that converts the R signal output from the image information detection device 32 into a V; It is comprised of a signal processing circuit 62 that converts the B signal into a density signal and performs δ and γ correction, and a signal processing circuit 64 that converts the B signal into a 1-variant signal and performs δ and γ correction. These signal processing circuits 6
0.62.64 has the same configuration, so the signal processing circuit 6
Only 0 will be explained. The signal processing circuit 60 includes an offset correction circuit 601, a logarithmic conversion circuit 602 for converting density signals, a δ correction circuit 603, and a γ correction circuit 604. The offset correction circuit 601 includes an operational amplifier OP3, resistors R6 and R7, and a variable power supply B1. The δ correction circuit 603 includes an operational amplifier OP4, resistors R6 and R7, and a variable power supply B2. Then, the R, G, and B signals are corrected by δ and γ and output.

The above-mentioned simulator 34 uses a logarithmic converter 341 connected to the output terminal of the gain control circuit 33, which matches the density (integral density) seen from the light receiving spectral sensitivity of the camera with the density seen from the receiving and light spectral sensitivity of the photographic paper. ×3 matrix (cubic square matrix) circuit 342, N/P inversion circuit 343 that inverts negative/positive (N/P) and converts it into analytical density of photographic paper, and converts analytical density of photographic paper into analytical density of CRT. It is constructed by sequentially connecting in series a luminance signal conversion circuit 344 for converting into an analytical forest product and a CRT 345 for displaying an image captured by the camera 30 by coloring a phosphor according to the output of the luminance signal conversion circuit 344.

1. The burden of characteristics Here, the value obtained by logarithmically converting each of the B, G, and R signals output from the camera 30 by the logarithmic conversion circuit 341, that is, the integral density of the color Gafilm image as seen from the light receiving spectral sensitivity of the camera is BT. V N G 't V % R' When converted into a negative analysis 7 degree using a 3×3 matrix A-' (where -1 indicates an inverse matrix) as Tv, the following equation is obtained.

Further, if the integral density of a color negative film image viewed from the spectral sensitivity of the photographic paper is B, , G, , R, and converted into negative analysis using a 3×3 matrix B-I, the following equation is obtained.

4 degrees of negative analysis in equation (2) (BTV
, G T v , R t v ) and (BP , GP , R
Since it is proportional to P ), it can be expressed as the following (3) 2 using a diagonal matrix α whose diagonal components are proportional constants.

Therefore, using the above equations (11 to (3)), (B, , GP
, R,) and (B tv, G'rv, R'rv), the following equation (4) is obtained, which allows T
The density determined by the spectral sensitivity of V is converted into the density determined by the spectral sensitivity of the photographic paper.

'o o. ,] Each component of each of the above matrices B and α is determined in advance for a sample such as a reference negative, taking into consideration the color development characteristics of color negative film, the spectral sensitivity characteristics of photographic paper, and the spectral sensitivity characteristics of the camera, and is calculated in the matrix shown below. is set in the 3×3 matrix circuit 342.

The N/P inversion circuit 343 is a circuit that converts γ to -γ, and converts the output of the 3×3 matrix circuit 342 according to the following straight line and outputs the converted signal.

)'-y+ = a (x-x+ )...(6) where, The coordinate value a is a constant, and a negative value is usually selected.

The above pivot point is the point where the density should not change even if the N/P is reversed, that is, the neutral gray (standard)
#Gray) Rehel points are selected.

Cameras and CRTs display a range from black level to white level in the range of 0 to 0.7■, so logarithmically converting the black level of the camera output results in 1■, and when N/P is inverted, C
For example, the black level may not be accurately inverted to the white level because the RT display range is exceeded. For this reason, N/
For P inversion, it is preferable to perform N/P inversion with a pivot point near 23% of the white level of the camera outputs V, .

Figure 4 shows the camera output V, , when N/P is inverted with 23% of the white level of the camera output V, , as the pivot point.
, , and N/P inversion circuit 343 output V out ゛
relationship is shown. Since the white level of the camera is 0.7V, 23% of the white level is 0.161V.

Here, the output of the 3×3 matrix circuit 342 is expressed as Y =
3.2518 + 1 og V l1l-(71, the coordinates corresponding to 23% of the white level are (0, 1
61, 2, 47). Therefore, (2, 47, 2, 4
7) Straight line y -2,47= a (x-2,47)...(8
), the curve expressed by the above equation (7) is converted to obtain the curve shown in FIG. 4, which is N/P inverted. As understood from FIG. 4, the value of 23% of the white level of the camera output remains unchanged even after the N/P inversion.

Further, in order to perform N/P inversion, the N/P inversion circuit may be configured with the circuit shown in FIG. 5, and the N/P inversion may be performed by finding a pivot point as described below. The circuit of FIG. 5 adjusts the reference voltage by moving the operational amplifiers OPI, GP2, the variable resistor R1 that sets the reference voltage V, , V, (corresponding to the pivot point) of the operational amplifier, and the contact of the variable resistor R1. It is equipped with an actuating mechanism AC that changes. A signal is input to the inverting input terminal of the operational amplifier OPI via a resistor R2, and a variable resistor R3 for adjusting the gain is connected between the inverting input terminal and the output terminal of the operational amplifier OP1. . The output terminal of the operational amplifier OPI is connected to the inverting input terminal of the operational amplifier OP2 via a resistor R4. A resistor R5 is connected between the inverting input terminal and the output terminal of the operational amplifier OP2. One end of the variable resistor R1 is grounded, the other end is grounded via a voltage aB, and the contacts of the variable resistor R1 are connected to the non-inverting input terminals of the operational amplifiers OP1 and OP2, respectively.

We will explain how to find the pivot (point) using the above circuit. First, a color negative film colored in standard gray is held between a negative carrier and imaged with a camera, and after N/P inversion is performed using the circuit shown in Figure 5. Next, a standard gray signal (which can be created electrically by setting the white level of the CRT to 23%) is displayed on the CRT screen in close proximity to the above negative image. and,
Operate the keyboard to continuously change the resistance value of variable resistor R] to base Y1! By changing the voltages V, , V, the negative image colored in standard gray is made to match the image generated electrically with the standard gray signal.

This determines the pivot point.

By using the above circuit, it is possible to set the gray level according to the sense of the measurer, and since it is possible to set the gray level according to the sense of the measurer, it is possible to match the finished state of the print. The gray level can be set, and thereby a highly accurate simulation can be performed including conditions such as development conditions (fatigue of the developer, temperature change of the developer, etc.).

Color\Special 11 CRTs display images using light emitters, so the brightness of a CRT is proportional to the voltage. However, since photographic paper uses an absorber (dye), the amount of dye and brightness are not proportional, but the amount of dye and the logarithm of brightness are proportional, and furthermore, changing the amount of dye changes the chromaticity. Change. In other words, the pigments in photographic paper are unstable primary colors (the chromaticity point of which changes with changes in color gt).
C, Y, M).

Therefore, the luminance signal conversion circuit 344 has N
The output of the /P inversion circuit 343 is converted into an analytic luminance (i-number T) and output on the CRT screen.

T=F (f o g-' CI (D)) )...
(9) However, f is a function that converts the output into an integrated density, and F is a function that converts the integral +3 error rate 10 g-' (D) into an analytical luminance signal.

The above-mentioned functions F and r are determined by determining the output value and the analytical luminance signal T to optimal values in advance, and performing optimization using the least squares method, regression, or the like. Note that for the SEK OF and f, a 3×3 matrix is used for boat fishing.

Then, the CRT is controlled by the luminance signal obtained by the luminance signal conversion circuit 344 as described above, and the CRT is
An image having coloring characteristics matching those of photographic paper is displayed on T.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the gain control circuit shown in FIG. 1, and FIG.
A circuit diagram showing an example of the δ and γ correction circuit shown in Fig. 4.
A diagram for explaining P inversion, and FIG. 5 is another circuit diagram for performing N/P inversion. 14...Dimmer filter, 27...Print, 34...Simulator.

Claims (1)

[Claims] (1) Correcting the γ of a simulator that takes an image recorded on film and displays the same image recorded on the photographic paper on the CRT by taking into account the γ characteristics of the CRT and the γ characteristics of the photographic paper. In this case, the γ characteristic of the CRT and the γ characteristic of the photographic paper are
A simulator gamma correction method characterized by simultaneously performing corrections corresponding to characteristics.