JP2680244B2 - How to confirm depth of field by simulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to visually recognize a depth of field at an arbitrary aperture value in an open aperture state by using an automatic subject distance measuring and autofocus function of an autofocus single lens reflex camera and a central processing unit. A method for confirming the depth of field by simulation.

[0002]

2. Description of the Related Art In photography, the depth of field is an important factor in determining the quality of image expression, but even a professional photographer sometimes finds an unsuitable depth of field. Depending on the depth setting, the work may fail. The smaller the aperture of the lens when taking a picture,
The depth of field is deeper. Also, the larger the aperture, the shallower the depth of field. If the aperture of the lens is reduced, the amount of incident light will decrease, and it will be difficult for the photographer to see the subject image in the viewfinder.Therefore, ordinary single-lens reflex cameras aim at the subject with the wide aperture and the aperture is pressed the moment the shutter button is pressed. It is equipped with an automatic aperture mechanism that exposes the aperture to a set value. Therefore, the depth of field of the open aperture that the photographer sees in the viewfinder is different from the depth of field of the actual shooting screen when the aperture value is equal to or less than the open aperture. Therefore, it may be necessary to determine the range of the depth of field in advance before pressing the shutter. A conventional method for determining the depth of field will be described below. Read the depth of field with the depth-of-field index marked on the lens barrel. In this method, the depth of field at a set aperture value is read by a scale that displays a different depth of field range for each aperture value. This method is inconvenient because it requires moving the line of sight from the viewfinder to the depth of field of the lens each time the aperture of the lens is changed. The focus range can be known, but the actual degree of blurring of the background or foreground cannot be known.

The depth of field of the screen of the finder is observed using the narrowing button of the single-lens reflex camera. When the aperture button is pressed, the aperture of the lens is reduced to the set aperture, but since the viewfinder screen with the reduced aperture is dark, it is difficult to visually recognize the depth of field and the degree of blurring of the background and foreground.

As described above, the conventional methods for determining the depth of field have various drawbacks, so that it is difficult to determine the depth of field.
Even a professional photographer can cause a work to fail due to a difference in depth of field when shooting.

Therefore, the degree of blurring of the background or foreground at the set aperture value and focal length can be visually recognized through the viewfinder with the open aperture, to reduce the depth of field judgment and error and to facilitate photography. Therefore, a problem to be solved occurs, and an object of the present invention is to solve the above problem.

[0006]

As a means for solving the above-mentioned problems, the present invention has a drawback that it is not easy to confirm the depth of field in a state where a diaphragm is narrowed in a conventional traditional camera. It is a modification of the. That is, using the autofocus mechanism, which is general hardware in current single-lens reflex cameras, and its central processing unit, the depth of field is calculated at any focal length setting and aperture setting, and the aperture remains open. It provides a method of visual confirmation of depth of field by simulating by expressing the degree of blurring in the setting of the aperture and focal length during actual shooting on the viewfinder image by moving the focus on a subject in the background or near view. is there. Thereby, the photographer can visually recognize the state of the depth of field at the set aperture value by observing the viewfinder image.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the conventional traditional single-lens reflex camera, when the aperture is not changed,
It has the drawback that the actual depth of field cannot be determined with the viewfinder. However, since the degree of automation of the current cameras such as automatic exposure and autofocus function has advanced, the autofocus function and the central processing unit are combined to calculate the depth of field, and the photographer is We have developed a unique simulation method that allows you to know the depth of field by observing from a viewfinder. The method and principle of the present invention will be described below.

The depth of field (focus range) of the lens is obtained by the following formula.

Depth of field distant limit point T _F = (D × f ² ) / (f ² −D × C × N) (1) Depth of field front limit point T _N = (D × f ² ) / (F ² + D × C × N) (2) where D = main subject distance f = lens focal length C = diameter of the circle of least confusion of the image that is the reference for focusing determination N = lens aperture value

By substituting the known number of each variable into the above two formulas, the depth of field far limit point T _F and the depth of field front limit point T _N can be obtained. Also, the diameter of the circle of confusion in the depth of field range can be calculated backward. Similarly, the sharpness of the background or foreground object to be observed can be calculated by using the above two formulas and further combining with the method of the present invention described below.

The depth-of-field calculation formula is not limited to the above-mentioned two depth-of-field calculation formulas, and various other depth-of-field calculation formulas are known, and other similar calculations. The formula can also be used to calculate the depth of field range, and the depth of field calculation results are also within the permissible range.

As shown in FIG. 1, when the camera is aimed at the main subject A, the distance D of the main subject A can be obtained by the autofocus mechanism. Then, move the camera to the background subject B (or foreground subject f) that you want to observe.
Aiming at the target, the distance T of the background subject B you want to observe
Can be requested. Substituting the background distance T and the aperture value N set by the photographer into Formula 1 or another formula for calculating the depth of field, the minimum confusion when the background object B is imaged on the film in the situation of the aperture value N. The circle C can be determined (use formula 2 if you observe the foreground f). Then, by substituting the obtained minimum circle of confusion C and the open aperture value of the lens into Formula 1 or another formula for simulating the depth of field, the distance Dnew of the virtual main subject A'can be obtained. After that, the auto focus mechanism is driven to focus the lens to the distance Dnew of the virtual main subject A '.
Transfer to At this time, the image of the background subject B viewed from the viewfinder can be seen with the sharpness on the film actually photographed at the set aperture value. With the above method and formula, the sharpness of the image of the foreground or background subject can be clearly seen from the viewfinder in a situation where the photographer cannot change the aperture, and thus the depth of field at the set aperture value can be known. obtain.

FIG. 2 shows a hardware system of the present invention. A central processing unit used for data processing, a distance measuring system for measuring a distance between an object and a camera, an aperture and a shutter speed required for accurate exposure are determined. Metering system for
It is composed of a zoom system for enlarging the object in the background or foreground to be observed and facilitating the determination of the sharpness of the subject, and an auto-focus mechanism that allows quick and accurate focusing and appropriate focus movement. .

The hardware configuration of the present invention is exactly the same as that of the current autofocus single-lens reflex camera. The present invention measures the distance between a main subject and an arbitrary subject before and after the main subject by a distance measuring system, and performs a simulation calculation of the depth of field by the above-described method by the central processing unit and further automatically by an autofocus system. Adjust the focus. That is, the degree of blurring when the subject is photographed at the set aperture value before or after the main subject in the state of being focused on the main subject is reproduced in the viewfinder image, and after confirming the degree of blurring, accurate blurring by the automatic metering system is performed. By shooting at the exposure value, the shooting effect intended by the photographer can be obtained. If a zoom lens is used, an object can be observed at a relatively long focal length using a zoom system in the depth-of-field observation process, and the sharpness can be easily determined.

FIG. 3 is a flow chart of the depth-of-field simulation method of the present invention, showing each operation step of the present invention. FIG. 4 shows a data processing process of software to which the present invention is applied, and shows each step of the simulation operation of the central processing unit of the present invention. First, the depth of field priority mode of the present invention is selected and set from various shooting modes such as the shutter speed priority mode and the program exposure mode. After that, the camera is moved to frame the shooting screen in the viewfinder, and an arbitrary aperture value Nold is determined. The distance Dold of the main subject is measured by aiming at the main subject, and the central processing unit stores data such as the lens focal length fold, the subject distance Dold, and the aperture value Nold.

After this, the photographer moves the camera and aims at an arbitrary subject in the background or in the near view whose degree of blurring is to be observed. If it is desired to magnify and observe this subject, the zoom system is used to change the lens focal length to the long focal length direction to magnify the subject image. Here, the distance measuring mechanism determines the distance T _F or T _{N of the} background or near object, and the central processing unit stores the data of the distance T and the focal length fnew. After the photographer completes operations such as framing, aiming, and zooming of the background subject, the central processing unit performs a simulation calculation of the depth of field. The first step of the depth of field calculation of the central processing unit is the distance T of an arbitrary subject in the background or the near view and the main subject distance Dold.
Is compared to determine whether any subject is the foreground or background of the main subject.

If the subject is a background subject, the following equation is adopted to obtain the minimum circle of confusion C on the real screen of the subject.

T _F = (Dold × fold ² ) / (fold ² −Dold × C × Nold) (3)

If the subject is a foreground subject, the following equation is adopted to find the minimum circle of confusion C on the real screen of the subject.

T _N = (Dold × fold ² ) / (fold ² + Dold × C × Nold) (4)

After calculating the minimum circle of confusion C of the actual screen of an arbitrary subject, the minimum circle of confusion C, the focal length fnew after zooming,
The virtual main subject distance Dnew is calculated by substituting the open aperture value Nnew of the lens into the above depth-of-field calculation formula. Besides, other formulas for calculating the depth of field may be adopted in the above steps. The value obtained by the calculation also meets the request.

After the central processing unit completes the simulation calculation of the depth of field, the autofocus system is driven to move the lens focus of the camera to the virtual main subject distance Dnew.
Transfer to At this time, the diameter of the circle of confusion C of the image of the background subject or the foreground subject due to the open aperture value Nnew is the distance D
old, the lens focal length fold, and the set aperture value Nold are equal to the diameter of the circle of confusion C of the actual captured image. Therefore, in the state of the open aperture value Nnew and the lens focal length fnew, the sharpness of the background or the near-distance subject in the actual photographing condition can be visually recognized by the viewfinder by the main subject distance Dold, the lens focal length fold, and the set aperture value Nold. .

If the photographer is dissatisfied with the sharpness of the background or near-field subject, the central processing unit performs a simulation calculation of the depth of field again by changing the set aperture value Nold, and further the focus fnew. Can be adjusted to allow the photographer to newly observe the degree of blur. The photographer can also magnify and observe the degree of blur by zooming the lens focal length to further magnify the screen.

After the sharpness of the background or near object has been met, the same observation can be performed on another object. After the observation is completed, the autofocus system of the camera automatically restores the focus to the main subject distance Dold, and also returns the lens focal length to fold. Therefore, the main subject is first restored to the framing state. After that, the amount of light is measured again by the photometry system, the shutter speed at the set aperture value is determined, and the photographer can shoot a good work simply by pressing the shutter.

3 and 4 of the present invention, the degree of blurring of the object is actually simulated, and the circle of confusion C is set to about 0.0 when the depth of field of the background or near object is calculated.
Temporarily set to 3 mm (which is regarded as the smallest circle of confusion for determining the focus in a 35 mm autofocus camera),
The depth-of-field range formula is used to directly determine the depth-of-field long-distance point T _F and the depth-of-field short-distance point T _N, which are displayed in the viewfinder in the form of numerical distance data for reference by the photographer. You may use it. In addition, the above-mentioned T _F and T _N are displayed in the viewfinder by an appropriate symbol such as a bar graph relative to the shooting distance, and the photographer also uses the depth of field range directly appearing in the viewfinder as a reference for shooting. Good. According to this, since the simulation of the depth of field due to the focus movement of the lens is not performed, the time required for shooting can be shortened.

[0026]

According to the present invention, it is possible to observe the sharpness of the background or near-view subject in the aperture setting at the time of shooting, while keeping the camera at the open aperture. Therefore, the depth of field in the set shooting state can be visually recognized accurately, and the photographer can adjust the degree of depth of field at any time while looking through the finder, and the operation is easy. Further, the sharpness of an arbitrary background subject or foreground subject can be confirmed, and the intended depth-of-field effect can be easily used for shooting.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the positions of a camera and a subject, and is an explanatory diagram of focus movement by a depth of field simulation.

FIG. 2 is an explanatory diagram of a control system of an automatic exposure autofocus camera.

FIG. 3 is a flowchart of a shooting operation according to the depth-of-field confirmation method of the present invention.

FIG. 4 is a data processing flowchart of the depth of field simulation of the present invention.

[Explanation of symbols]

 A main subject A'virtual main subject B background subject F near-field subject D main subject distance Dnew virtual main subject distance T background subject distance

Claims (4)

(57) [Claims] 1. A method of confirming a depth of field by a simulation, which is capable of confirming the depth of field at a set aperture value in a viewfinder image without performing a lens aperture operation in an autofocus camera, comprising: a. Set a calculation formula to calculate the depth of field based on each parameter of aperture value, lens focal length, and subject distance b. Measurement of the main subject distance DoId and the distance T of the foreground or background object by the autofocus mechanism of the camera c. Lens focal length foI at main subject distance DoId
Calculation of d d. Setting of arbitrary first aperture value NoId for shooting e. Reading a second aperture value Nnew, which is an aperture value when observing an object with a viewfinder of the camera, in the camera f. Main subject distance DoId, foreground subject or background subject distance T, lens focal length foId, and first aperture value NoI
d, substituting the second aperture value Nnew into the calculation formula, the image sharpness of the foreground subject or the background subject in the state of the first aperture value NoId at the main subject distance DoId, and the second aperture value Nnew A virtual main subject distance Dnew at which the image sharpness of the foreground subject or the background subject in the state is equal to g. The focus of the lens is moved from the main subject distance DoId to the virtual main subject distance Dnew by the autofocus mechanism of the camera. By executing the above steps, the virtual sharpness of the foreground subject or the background subject in the state of the first aperture value NoId. Depth of field confirmation method by simulation in which the degree is shown in the viewfinder in the state of the second aperture value Nnew. 2. A method of confirming a depth of field by a simulation, which is capable of confirming the depth of field at a set aperture value in a viewfinder image without performing a lens aperture operation in an autofocus camera, comprising: a. The depth of field calculation formula adopts the following formula: (i) When collimating a foreground subject: T = (D × f ² ) / (f ² + D × C × N) (ii) a background subject When collimating: T = (D × f ² ) / (f ² −D × C × N) In the above formula, D: main subject distance T: foreground or background subject distance f: lens focal length C : Diameter of circle of least confusion in image of foreground subject or background subject N: Aperture value of lens b. The steps of estimating the virtual subject distance are as follows: (i) Using the formula, the main subject distance Dold and the lens focal length foId measured through a distance measuring mechanism.
Is substituted into the variables D and f in the formula, the distance T of the foreground or background object is substituted into the variable T, and the arbitrarily set first aperture value Nold is substituted into the variable N,
A minimum confusion circle diameter C of the foreground subject image or the background subject image is calculated. (ii) Substituting the minimum confusion circle diameter C into the formula variable C, the distance T of the foreground subject or the background subject to the variable T
, The second aperture value Nnew is assigned to the variable N, and the lens focal length foId is assigned to the variable f to calculate a variable D. The value of the variable D is the virtual subject distance Dnew. (iii) When the zoom lens of the camera is zoomed, the focal length fnew of the lens after zooming is substituted as the variable f in step b (ii). The depth of field confirmation method by simulation according to claim 1, wherein the above steps are executed. 3. A depth-of-field confirmation method by simulation, which enables the depth-of-field at a set aperture value to be confirmed in a viewfinder image without performing a lens aperture operation in an autofocus camera. 3. The simulation according to claim 1, wherein the step of calculating the virtual subject distance Dnew and the step of moving the focal point of the lens to the virtual subject distance Dnew are repeated according to the change of the value NoId. Depth of field confirmation method by. 4. A method of confirming a depth of field by a simulation, which is capable of confirming a depth of field at a set aperture value in a viewfinder image without performing a lens aperture operation in an autofocus camera. The method for confirming depth of field by simulation according to claim 1 or 2, wherein the value Nnew is a maximum aperture value of the lens of the autofocus camera.