JP3137967B2 - TTL division photometry method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a TTL split metering device, in which a luminous flux to be directed to a portion of a split subject screen into a photometric device enters an adjacent other photometric device and erroneous photometry is performed. The present invention relates to a method and an apparatus for preventing occurrence and obtaining a correct photometric value.

(Problems of the Related Art and Invention) In the case of using the SPD as the photometric element in the TTL split photometry, considering the split photometry on the subject screen as shown in FIGS. In an ordinary photometric optical system, a part reaches the central part, and a part of the light that should reach the central part reaches the peripheral part.

When a flat light source is viewed using an ideal optical system, the photometric distribution at the center is as shown in FIG. 2, but in reality, the luminous flux is spread as described above, and as shown in FIG. Become. Third
The hatched portion in the drawing is a portion where a part of the light in the peripheral portion reaches the central portion, and extra light is provided in the central portion. Conventionally, a complicated optical system was required to prevent this.

(Means for Solving the Problems) In view of the above-described circumstances, the present invention provides a partial photometry unit that performs photometry of one area of a multi-divided subject screen subjected to TTL division photometry, A light flux from a photometric surface which is provided with another photometric means for performing photometry in another area except for one area, and a computation storage means for computing the photometric output of these photometric means and storing the data; Does not affect the partial photometric means (EVa) and the output (EVa) of the partial photometric means when the two photometric means receive a luminous flux from a photometric surface having no luminance difference
A) and the output (EVB) of the other-part photometry means are measured in advance, and a correction coefficient K is obtained in advance by the equation EVa = EVA-K · 2 ^(EVB-EVA). A TTL division photometry method characterized by obtaining a photometry output that is not affected by a light beam from another portion photometry means by reducing terms.

Further, a partial photometric unit that performs photometry in one area of the multi-divided subject screen that is subjected to TTL division photometry, and another unit photometric unit that performs photometry in another area excluding the one area of the screen, It receives the output (EVa) of the partial photometric means when the light flux from the photometric surface received by the other part photometric means does not affect the partial photometric means, and the light flux from the photometric surface where there is no difference in luminance between the two photometric means. The output of the partial photometer (EVA) and the output of the other photometer (EVB) are measured in advance and the correction coefficient K calculated by the equation EVa = EVA−K · 2 ^(EVB−EVA). TTL division photometry characterized by comprising: a storage device for preliminarily storing the photometry output and calculating a photometry output that is not affected by the luminous flux from the other photometry unit based on the outputs of the two photometry units and the correction coefficient K. Provide equipment.

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

FIG. 1 is a view of an embodiment of the apparatus of the present invention, FIG. 2 is a photometric distribution diagram of a central portion when a flat light source based on ideal optics is viewed, and FIG. FIG. 4 is a diagram showing an example of division of a subject screen, and FIG. 5 is a diagram showing an example of division of another subject screen.

In FIG. 1, SPDs 1, 2, 3, 4, and 5 respectively correspond to A, B, C, D, and E in FIG.
The photocurrent generated from D is logarithmically compressed by a logarithmic compressor 6, A / D-converted by an A / D converter 7, and a computing unit 8 of a photometric optical system which uses the luminance difference between the respective parts as a parameter, which will be described later. The operation of calculating the correction formula and obtaining the true photometric value is performed. 9 to 13 are switches, and 14 is a regulator.

Next, the correction formula will be described. For simplicity of description, the two-division system shown in FIG. 4 will be described. Assuming that the true EV value (exposure value) to be measured is EVa, the EV value including the influence of the spread of the luminous flux in the adjacent photometric region is EVA, and the correction coefficient is K, the brightness is uniform between the central portion A and the peripheral portion B. When the light flux is received from the photometry surface and photometry is performed, the true EV value of the central portion A can be obtained by the following equation: EVa = EVA−K (1)

Therefore, the EV of the central part A is brighter than the peripheral part B.
By measuring the value EVa, and then irradiating both the central portion A and the peripheral portion B with a light beam having the same brightness, and measuring the EV value EVA of the central portion A, the correction coefficient K becomes K = EVA−EVa. ··· (2)

If the correction coefficient K is stored in the arithmetic unit 8, a true EVa value of the central portion A when the central portion A and the peripheral portion B have the same luminance can be obtained.

However, the brightness of the central portion A and the peripheral portion B may naturally be different. For example, if the brightness doubles, the correction coefficient K
Also needs to be doubled.

Therefore, the peripheral portion B including the influence of the spread of the luminous flux
Assuming that the EV value is EVB, the true EVa value can be obtained from the equation EVa = EVA−K · 2 ^(EVB−EVA) (3).

As described above, the correction coefficient K is determined by taking the difference between the EV value affected by the spread of the luminous flux and the EV value not affected by the spread of the luminous flux as the influence component. This is applicable to the case of multi-division as shown in FIG. In this case, the correction equation is as follows.

EVa = EVA-Kb · 2 ^(EVB-EVA) -Kc · 2 ^(EVC-EVA) -Kd · 2 ^(EVD-EVA) -Ke · 2 ^(EVE-EVA) · · (4) C, D, E
The EV value of each section is EVC, EVD, and EVE, and the correction coefficient is K
Here, b, Kc, Kd, and Ke are obtained. Kb is obtained by Expression (3), and other coefficients are obtained in advance by applying Expression (3). Note that this correction may cause some errors,
By using the corrected value for the exponent of 2 in Equation 3 or Equation 4 and performing correction twice or many times, accurate correction can be achieved.

(Effects) As described in detail above, according to the present invention, accurate TTL division photometry can be performed with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a view of an embodiment of the apparatus of the present invention, FIG. 2 is a photometric distribution diagram of a central portion when a flat light source is viewed by an ideal optical system, and FIG. FIG. 4 is a diagram showing an example of division of a subject screen, and FIG. 5 is a diagram showing an example of division of another subject screen. 1 to 5 SPD, 6 logarithmic compressor, 7 AD converter, 8 arithmetic unit, 9 to 13 switches, 14 regulator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 1/44 G03B 7/28

Claims (2)

(57) [Claims] 1. A partial photometer for taking light metering of one area of a multi-divided subject screen subjected to TTL split photometry, and another part metering taking charge of photometry of another area excluding said one area of the screen. Means for calculating the photometric output of these photometric means and storing the data, wherein the light beam from the photometric surface received by the other photometric means does not affect the partial photometric means. The output (EVa) of the partial photometer, the output (EVA) of the partial photometer and the output (EVB) of the other photometer when the two photometers receive the luminous flux from the photometric surface having no difference in luminance. Measure in advance and E
Va = EVA−K · 2 ^{(EVB−EVA) The} correction coefficient K is obtained in advance and the photometric output not affected by the luminous flux from the other photometric means by subtracting the term of the correction coefficient K from the photometric output. TTL split metering method characterized by obtaining 2. A partial light metering means for performing light metering of one area of a multi-divided subject screen subjected to TTL split metering, and another light metering section for performing light metering of another area other than the one area of the screen. Means, an output (EVa) of the partial photometric means when the light flux from the photometric surface received by the other photometric means does not affect the partial photometric means, The output (EVA) of the partial photometer and the output (EVB) of the other photometer when the light beam is received are measured in advance, and E
Va = EVA−K · 2 ^{(EVB−EVA) The} correction coefficient K calculated and calculated by the equation ^(EVB-EVA) is stored in advance, and the output of the two photometric means and the correction coefficient K affect the luminous flux from the other photometric means. A TTL division photometric device, comprising: an arithmetic storage unit for calculating a photometric output that is not performed.