JP2875830B2 - camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, and more particularly, to a camera capable of improving a shooting image quality in shooting using an illumination light source.

[Prior Art] In the case of photographing using an illumination light source such as a strobe of an electronic photographing system, the incident light intensity / photosensitive level on the photosensitive recording system side constituted by a photographing element and a signal processing circuit in the succeeding stage. If the ratio characteristics (gradation characteristics) are performed under the same conditions as in the case of shooting with natural light, phenomena such as overexposure are likely to occur. This phenomenon is particularly remarkable particularly when photographing a deep subject. For example, FIG. 9 shows the relationship between the distance at the time of flash emission and the amount of reflected light.
When the subject at point B and C is photographed in one screen, the subject at point A is too bright and overexposed, even if proper exposure is given to point B at the center. Become. This is a problem that occurs particularly remarkably because the dynamic range of the photosensitive recording system is extremely narrow as compared with the conventional silver halide film. A technique disclosed in Japanese Patent Application Laid-Open No. Sho 59-196664 has been proposed to solve the problem. This proposal is characterized by changing the γ characteristic, which is an important parameter representing the gradation characteristic, in order to keep the output voltage within the above narrow dynamic range, especially during flash photography.

[Problems to be Solved by the Invention] However, the one disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-196664 applies gamma correction to the photographing signal in the entire range. However, there is a problem that the temperature is also lowered.

A first object of the present invention is to solve the above-mentioned problems,
A second object of the present invention is to provide a camera capable of securing a dynamic range while maintaining contrast with respect to a main subject in photographing with an illumination light source. It is another object of the present invention to provide a camera characterized in that an excellent gradation characteristic can be obtained.

[Means and Actions for Solving the Problems] The camera of the present invention uses a light-sensitive output level characteristic with respect to incident light intensity on the light-sensitive recording system side at the time of shooting using an illumination light source. A camera having light-sensitive output characteristic varying means for obtaining a second characteristic different from the characteristic described above, wherein the light-sensitive output characteristic varying means substantially corresponds to the main subject. The portion is set so as to substantially match the first characteristic and to be different only in the other portion. Detecting means for detecting the distribution; and the light-sensitive output characteristic varying means has a plurality of the second characteristics, and the plurality of second characteristics correspond to the output of the detecting means. Any of The characteristic is characterized in that the characteristic can be selectively applied.

Hereinafter, the present invention will be described with reference to the embodiments shown in the drawings.

FIG. 1 is a block diagram of a camera showing one embodiment of the present invention, but shows only those relevant to the gist of the present invention. The photographic light beam taken in through the photographic lens 1 is converted into a photographic signal by a photographic element 3 having an element shutter function via a diaphragm device 2. Then, the image signal is processed by an imaging signal processing circuit below the S / H circuit 5 controlled by the system controller 4. That is, S / H
The sample and hold processing is performed by the circuit 5, and the luminance signal Y,
Color signals R, G, and B are separated. After that, after the band is limited by the LPF circuit 6, the partial gradation compression circuit 7 and the gamma processing circuit 8, which are the light sensitivity characteristic varying means described later, perform gradation compression processing according to each specified condition described later. , Γ correction is performed. Note that this process is based on the luminance signal,
Performed individually for each color signal. The matrix circuit 9 converts the signals into color difference signals R-Y and B-Y, which are output together with the luminance signal Y to an imaging circuit at the next stage or lower, and are recorded or reproduced as video signals. The imaging device 3 and the imaging signal processing circuit below the S / H circuit 5 constitute a photosensitive recording system.

On the other hand, the aperture operation of the aperture device 2 is performed via the exposure control driver 10 controlled by the system controller 4, and the charge accumulation time of the image sensor 3 is controlled. In addition, the controller 4 controls light emission of the strobe light emitting means 11 serving as an illumination light source. Further, the distance measuring signal of the distance measuring sensor 12 which is a detecting means for detecting the positional distribution of the subject is transmitted to the controller 4.
The tone compression circuit 7 is controlled based on the distance measurement data. Operation switch means
The user selects and designates a gradation compression mode, a strobe shooting mode, a multi-distance measurement mode, and the like by the user 13.

The distance measuring sensor 12 is an active type multi-beam sensor, the details of which will be described with reference to FIG. The distance measuring sensor 12 includes a light projecting unit and a light receiving unit. In the light emitting section, a driver circuit 23 controlled by a distance measurement control signal output from the system controller 4 causes the LEDs 22a, 22b, and 22c of the three light emitting elements to emit light at predetermined timings. Then, the light is projected as a distance measurement beam to the subject 20 via the light projecting lens 21. The ranging beams are C beam in the center direction, R beam in the right direction, and L beam in the left direction.
It consists of two beams. On the other hand, the light receiving section takes in the three reflected beams from the subject through the light receiving lens 24, and the distances l _C , l _R and l _{L in} the above three directions on the PSD 25 of the optical position detector.
Is detected and the subject distance of each object is measured. It should be noted that a passive distance measuring sensor using a one-dimensional linear sensor can be used as the distance measuring sensor.

The configuration and operation of the partial gradation compression circuit 7 will be described with reference to the circuit diagram of FIG. 3 and the characteristic diagram of FIG. As shown in FIG. 3, the compression circuit 7 has a resistance value r ₁
Dividing resistor R ₂ and the analog switch SW with a resistance R ₁ and a diode D ₁ and the resistance value r _2, which is connected in series with a
₁ and a DC power supply Ba having a voltage Ea. Further, e is an input voltage, and E is an output voltage. FIG. 5 is an output characteristic diagram of the compression circuit 7, wherein the horizontal axis and the vertical axis represent the input voltage e and the output voltage E, respectively. Since the input voltage e corresponds to the output signal of the image sensor 3, it has a value proportional to the luminance of the subject.

The analog switch SW ₁ is ON, OFF control by the system controller 4, first, when OFF, the constantly input, the output voltage is equal, the fifth diagram of characteristic lines O～P ₀
Is output. In this case, the inclination angle θ _{0 of the} characteristic line
Is 45 °. This characteristic is referred to as a first characteristic, and is applied at the time of photographing without using an illumination light source. On the other hand, based on the gradation compression instruction from the system controller 4, when the analog switch SW ₁ is set to ON state by the control signal, until the output voltage or the input voltage reaches the Ea or e _a, the output characteristic line Inclination angle θ as above
Comes to have a _zero, a current flows output voltage via the voltage dividing resistors R ₂ exceeds Ea. The output characteristics will have a tilt angle theta ₁ characteristic between the points Pa～P _2, while the input voltage e _a to e ₂ is to be output after being compressed to a voltage EA to ED. That is, the dynamic range that can be detected is widened from the input voltage e ₁ to e _2.

Note that this inclination angle θ ₁ is Becomes Therefore, the characteristics of when the switch SW ₁ is ON break points P
A knee characteristic having a will be exhibited. This characteristic is referred to as a second characteristic, and is applied at the time of photographing when an illumination light source is used. In the second characteristic, the range of the input voltage indicated by the range M within the inclination angle θ ₀ common to the first characteristic substantially corresponds to the luminance from the region where the main subject exists.

A modification of the partial gradation compression circuit 7 will be described with reference to FIGS. This modified example has two break points Pb and Pc while the characteristic line has one break point in the case of the above embodiment. In the circuit diagram of FIG. 4, will be described only schematics and different parts of FIG. 3, the analog switch SW ₂ is in the OFF state, the voltage dividing resistors R ₃ having a resistance value r ₃ and the DC power source Bb voltage Eb diode D ₁ is connected in series circuit side. Then, in the ON state is configured to diode D ₁ in series circuit side of the dividing resistor R ₄ has a resistance r ₄ and DC power supply Bc voltage Ec is connected.

Its properties are as shown in FIG. 6, firstly when the analog switch SW ₂ is in the OFF state, until the output voltage Eb (equal to the input voltage e _b), characteristic curve a as 45 ° of the inclination angle theta ₀ (the In the region where the output voltage exceeds Eb, the inclination angle θ
Becomes a characteristic line with a _2, a region between the input voltage e _b to e ₃ are grayscale compression. In the present modification, such characteristics are referred to as first characteristics. Note that the inclination angle θ ₂ is Indicated by

When the analog switch SW ₂ of the is turned ON state based in part gradation compression instruction, the characteristic line to reach the output voltage Ec (equal to the input voltage e _c), the inclination angle similarly θ ₀ , but when it exceeds the output voltage Ec, the inclination angle θ ₃
become. Note that the inclination θ ₃ is represented by the following equation.

Accordingly, the scope of the maximum input voltage is high from e ₃ to e _4, it becomes a region where the range of input voltage e _c to e ₄ are strongly grayscale compression. Such a characteristic is referred to as a second characteristic in the case of the present modification. Also in the second characteristic, in the range in which the inclination angle θ ₀ is particularly common to the first characteristic, the input voltage region in the range M corresponds to the luminance from the region where the main subject exists. .

Next, the gradation compression characteristic selection operation by the camera of the embodiment shown in FIG. 1 will be described with reference to the flowchart of the gradation compression selection processing routine of FIG. First, prior to the above-described compression selection processing, the flags for the respective processing modes shown in Table 1 are set by the operation switch means 13.
Thereafter, the gradation compression characteristic selection processing routine is called. Regarding the flag FB, the flag is also set when the flash photography is automatically selected regardless of the operation switch means 13.
FB may be set to one.

First, in step S11, the gradation compression flag FA is checked. If the flag FA is 0 and the mode is the conventional mode in which the gradation compression processing is not performed, the weak compression characteristic, which is the normal processing in step S17, is selected, and the first characteristic, that is, the compression circuit 7 Or a characteristic such that only weak compression is performed.

If the flag FA is set to 1 in step S11, the mode is the gradation compression processing mode, and
Proceed to S12. Then, it is checked whether or not the flash photography is performed by the flag FB. If the flag FB is 0, the flash is not used, and the process jumps to step S17.
On the other hand, if the flag FB is set to 1, the mode is the flash photography mode, and the process proceeds to step S13, where the multi-ranging sensor 12 measures the distance. If the distance measurement is performed immediately before the present processing routine, this data may be used.

Subsequently, in step S14, it is determined whether or not to use the multi-ranging data. If the flag FC is 0 and the designation not to use the ranging data is made, the process jumps to step S16. If the fluff FC is set to 1 and it is specified to use the distance measurement data, the process proceeds to step S15, and the distance measurement sensor 12 measures the object distance in three directions. The distribution of the subject in the front-rear direction is determined based on the data, and if the distribution is within a distribution range described later, the process jumps to step S17 because the gradation compression process is unnecessary. If it is out of the range, step S16
The processing proceeds to select the strong compression characteristic. That is, the switch SW ₁ of the circuit 7 shown in FIG. 1 in the ON state,
As described above, the second characteristic is selected in which the input / output relationship of the compression circuit 7 performs strong gradation compression in a region where the light amount is equal to or more than a predetermined light amount.

The range of the determination of the subject distribution in step S15 will be described in detail. In the present embodiment, when the luminance of the peripheral object with respect to the luminance of the central object falls within +1 Ev, overexposure or the like due to dynamic range over without the strong compression correction using the second characteristic described above is performed. Is set as a criterion that the above phenomenon does not occur.
Therefore, in general, the amount of illumination light L on a subject is inversely proportional to the square of the subject distance l, so that the above condition of the luminance ratio can be converted to the condition of the subject distance. That is, when the following expression is satisfied, the strong compression correction is not required.

Here, l _C , l _R , and l _L are the distances to the subject measured in the central, right, and left directions, respectively, by the distance measuring sensor 12 as described above. If it is determined in step S15 that the distribution of the subject satisfies the above expression (4), the process jumps to step S17. If it is determined that the distribution is not satisfied, the process proceeds to step S16 to select the strong compression characteristic. become.

Regarding the above-mentioned second characteristic with respect to the compression characteristic, in the present embodiment, as shown in FIGS. 5 and 6, one characteristic line is applied as each of the second characteristic lines. It is also possible to set things and select them according to the characteristics.

Next, a case where the present invention is applied to selection of a gradation compression characteristic at the time of macro shooting as a camera of another embodiment will be described. Compared to macro shooting without using a flash or normal flash shooting without using a macro, the overexposure phenomenon tends to occur particularly in macro shooting using a flash. In this embodiment, the electronic image pickup system has a partial gradation compression circuit, and the strong compression characteristic, which is the second characteristic described above, is selected in the compression processing in connection with macro photography using a strobe. FIG. 8 shows a flowchart of the gradation compression characteristic selection processing routine. First, in step S21, it is determined whether or not the flash shooting macro photography is set. If not set, the process jumps to step S23, and if set, the process proceeds to step S22. Step S
In 23, strong compression is not required, and weak compression, that is, normal compression characteristics is selected. In step S22, the above-described second characteristic of the strong compression processing is selected, and this routine ends.

[Effects of the Invention] As described above, the camera of the present invention provides a light-sensitive output capable of selecting a first characteristic for photographing without using an illumination light source and a second characteristic having different characteristics in a light-sensitive recording system. A characteristic varying unit is provided. In the second characteristic, a portion substantially corresponding to the main subject is assumed to coincide with the first characteristic, and the first or second characteristic is selected based on a photographing condition. Things.

Therefore, according to the present invention, when used together with an illumination light source, it is possible to perform shooting while securing a wider dynamic range than during normal shooting while maintaining the contrast with respect to the main subject, that is, the gradation characteristics. Further, it is possible to provide a camera having a remarkable effect such that an optimal gradation characteristic can be obtained according to the distribution of the subject when used together with the illumination light source.

[Brief description of the drawings]

FIG. 1 is a block diagram of a camera showing one embodiment of the present invention, FIG. 2 is a diagram of a distance measuring sensor of the camera of FIG. 1, and FIG. 3 is a diagram of the camera of FIG. FIG. 4 is a partial gradation compression circuit diagram showing a modification of the compression circuit of FIG. 3, FIG. 5 is a characteristic diagram based on the compression circuit of FIG. 3, FIG. 6 is a characteristic diagram based on the compression circuit of FIG. 4, FIG. 7 is a flowchart of a gradation compression characteristic selection process in the camera of FIG. 1, and FIG. 8 is another embodiment of the present invention. FIG. 9 is a flowchart of a macro photographing gradation compression characteristic selecting process in the camera showing an example. FIG. 9 is a diagram showing a change curve of a light amount with respect to a subject distance. 3. Image pickup element (photosensitive recording section) 5. S / H circuit (photosensitive recording section) 6. LPF circuit (photosensitive recording section) 7. Partial gradation compression circuit (photosensitive recording system) (Light-sensitive output characteristic variable means) (Light-sensitive recording staff) 8 ... Gamma processing circuit (Light-sensitive recording staff) 9 ... Matrix circuit (Light-sensitive recording staff) 12 ... Distance measuring sensor (Position distribution of subject distance) Detecting means for detecting

Claims (2)

(57) [Claims] In the photographing using an illumination light source, a characteristic of a light-sensitive output level with respect to an incident light intensity on a light-sensitive recording system is set to a second characteristic different from the first characteristic when no illumination light source is used. A light-sensitive output characteristic varying means, wherein the second characteristic of the light-sensitive output characteristic varying means is substantially the same as the first characteristic for a portion substantially corresponding to a main subject. And a camera which is set so as to be different only in other portions. 2. A characteristic of a light-sensitive output level with respect to an incident light intensity on a light-sensitive recording system side during photographing using an illumination light source is set to a second characteristic different from the first characteristic when no illumination light source is used. Camera having light-sensitive output characteristic variable means for detecting a positional distribution of a subject,
In addition, the light-sensitive output characteristic varying unit may have a plurality of the second characteristics, and any one of the plurality of second characteristics may be selectively applied according to the output of the detection unit. A camera characterized in that: