JPH0157770B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camera that uses both average and partial photometry.

Among the objects to be photographed by a camera, there are those that have small differences in brightness overall and are suitable for average photometry, and those that have particularly high or low brightness in some areas and are suitable for partial photometry. Therefore, in order to perform optimal photometry for any subject, it is desirable to use average photometry and partial photometry. Therefore, cameras have been provided that have both average and partial photometry functions.

Here, there are cases where average and partial photometry alone are insufficient and an auxiliary light is required. For example, when the background is high brightness and the subject is low brightness.

Conventionally, in such cases, the necessity of using an auxiliary light has been determined empirically.

However, such a photographing operation that involves complicated judgments does not meet the demand for simplifying the photographing operation due to recent camera automation.

An object of the present invention is to provide a camera photography control device that can automatically select one mode among average metering mode, partial metering mode, and average metering mode using auxiliary light based on both normal and partial metering contents. be.

The figure shows the circuit configuration of an embodiment of the present invention, in which the outputs of a partial photometry circuit and an average photometry circuit are compared, and the output of one of the photometry circuits is selected and applied to the arithmetic circuit. and a circuit that compares the outputs of the two photometric circuits and generates an output in electric flash mode (hereinafter simply referred to as EF mode) when auxiliary light emission is required.

PD _S is a photosensitive element for partial photometry, and is combined with an operational amplifier _OAS equipped with a logarithmic compression element as a feedback element, and its output is sent to an analog switch.
AS ₁ and two comparators CO ₁ and CO ₂ . Variable resistors VR ₁ and VR ₂ are shown in the signal path from the operational amplifier _OAS to the comparator CO ₁ and further to the comparator CO ₂ , respectively. PD _A is a photosensitive element for average photometry, and is combined with an operational amplifier OA _A equipped with a logarithmic compression element as a feedback element, whose output is sent to an analog switch AS ₁ and two comparators CO ₁ and CO _2. give.

Comparator CO ₁ is analog switch ₁ and AS ₁
The output is sent to the analog switch via a switch circuit consisting of a pair of analog switches AS ₂ , ₂ and a transistor Q.
Given to the control terminal of AS ₁ , ₁ . The display element changes as the analog switches AS ₁ and ₁ open and close.
Displays the lighting of L _A and L _S. Another comparator, CO ₂ , emits auxiliary light, and its output is
It is applied to the EF mode output terminal as well as to the EF mode display element _LEF for light emission display, and is further applied to the control terminals of a pair of analog switches AS ₂ and AS ₂ to control their opening and closing. The display elements L _S , L _A , and L _EF are arranged, for example, within the viewfinder.

Now suppose that the output given from the operational amplifier OA _A to the comparator CO ₂ is the output from the operational amplifier OA _S to the variable resistor VR ₁ ,
An EF mode output occurs when the output is greater than the output provided to the comparator CO ₂ via VR ₂ by a predetermined value. This predetermined value is determined by the settings of variable resistors VR ₁ and VR ₂ , of which VR ₁ is determined when the sum of the partial photometric value and the voltage drop due to variable resistor VR ₁ is smaller than the average photometric value by a certain degree. VR ₂ is used to set the value to be added to the sum of the partial photometry value and the voltage drop across variable resistor VR ₁ . . Here, comparator CO ₁ produces an output when the partial photometric value is not smaller than the average photometric value by a certain degree, and this output is given to the control terminals of analog switch ₁ and AS ₁ via the switch circuit. Used for opening/closing control, while comparator
Conversely, CO ₂ produces an output when the average photometric value is larger than the partial photometric value by a predetermined value, and this output is used to control the opening and closing of analog switches ₂ and AS ₂ of the switch circuit.

Figure 2 shows the partial photometry signal in the circuit of Figure 1.
This figure shows the relationship between the magnitude of the difference between V _S and the average photometric signal V _A (V _S −V _A ) and the operating mode. In other words, the range in which the partial photometry value is at the same level as the average photometry value, and the range in which the partial photometry value is at the same level as the average photometry value, are variable resistance.
The average photometry mode will be used up to the low level range within the VR ₁ setting value, and the partial photometry value will become a lower level beyond that, and the variable resistor will change to the VR ₁ setting value.
It becomes partial metering mode in the range where the level is lower than the average metering value up to the VR ₂ setting value. and,
The difference between the average photometric value and the partial photometric value is the variable resistor VR ₁ ,
If it is larger than the sum of both settings of VR ₂ ,
It becomes EF mode, and at this time it becomes average metering mode. This is because it is convenient when daylight synchronized photography is assumed.

This type of operation mode switching is done using a comparator.
Analog switch ₁ , AS ₁ for CO ₁ , CO ₂ output
and ₂ , performed by AS ₂ being driven. That is, when comparator CO ₂ does not produce an EF mode output, analog switch ₂ is open and AS ₂ is closed. At this time, the output of comparator CO ₁ is passed through analog switch ₂ to analog switch ₁ ,
It is applied to the control terminal of AS ₁ , and mode switching between average photometry and partial photometry is performed. On the other hand, the comparator CO ₂
When the EF mode output occurs, the analog switch
₂ is closed and AS ₂ is open. At this time, the output of comparator _CO1 is the transistor Q acting as an inverter.
After that, it is applied to the control terminals of analog switches ₁ and AS ₁ via analog switch AS ₂ , so the output of comparator CO ₁ is inverted and applied to analog switches ₁ and AS ₁ . This causes the camera to switch to average metering mode when in EF mode.

As described above, the present invention compares the average photometry value and the partial photometry value in a camera that uses both average photometry and partial photometry, and calculates the average value depending on whether or not these two photometry values have a predetermined magnitude relationship. Since one of the photometry mode, partial photometry mode, and average photometry mode using auxiliary light is selected, the photographing conditions can always be automatically made favorable.

[Brief explanation of drawings]

1 and 2 are a circuit diagram and an operation explanatory diagram showing one embodiment of the present invention. PD _S , PD _A ...photosensitive element, L _S , L _A , L _EF ... display element, OA - operational amplifier, CO... comparator.

Claims (1)

[Scope of Claims] 1. A first photometric circuit that performs average photometry, a second photometric circuit that performs partial photometry, and an exposure calculation that performs calculations based on the photometric output of the first or second photometric circuit. circuit; first and second comparators that output a selection signal and an auxiliary light emission signal in accordance with photometric outputs of the first and second photometric circuits; 1
and a switching circuit that selects one of the outputs of the second photometric circuit and applies it to the exposure calculation circuit, and the first comparator selects one of the outputs of the second photometric circuit and applies it to the first photometric circuit. The difference in output is the first
outputting a selection signal that selects the output of the first photometric circuit when it is less than a predetermined amount, and selects the output of the second photometric circuit when it exceeds the first predetermined amount; The comparator outputs an auxiliary light emission signal when the output of the second photometric circuit is smaller than the output from the first photometric circuit by an amount equal to or more than the first predetermined amount plus the second predetermined amount. A photographing control device for a camera that uses both average photometry and partial photometry, and outputs a selection signal for selecting the output of the first photometry circuit.