GB2132369A

GB2132369A - Apparatus for flash photography

Info

Publication number: GB2132369A
Application number: GB08326714A
Authority: GB
Inventors: Gottfried Konig; Claus Kuhnel; Udo Postel
Original assignee: Pentacon Dresden VEB
Current assignee: Pentacon GmbH Foto und Feinwerktechnik
Priority date: 1982-12-01
Filing date: 1983-10-06
Publication date: 1984-07-04
Also published as: DD212121A1; DD212121B1; DE3332835A1; GB2132369B; GB8326714D0; DE3332835C2

Abstract

The invention relates to an apparatus for flash photography with flash units which are attachable to a camera or are integrated components thereof. The apparatus comprises an indicator 10 for indicating that the flash will be adequate for a correct film exposure, a radiation emission system e.g. for infra-red, which is independent of the flash emission and directs radiation on to the picture subject, and a detector 3 for sensing the radiation which is reflected-back. The output signal of the detector (3) is fed, together with signal values characteristic of the guide number of the flash unit, film sensitivity and preselected diaphragm aperture, to a computer unit (4) which is followed by the indicator (10) for the preliminary indication of expectable incorrect flash exposure and/or correct flash exposure. <IMAGE>

Description

SPECIFICATION Apparatus for flash photography The invention relates to an apparatus for flash photography with flash units which are attachable to a camera or are integrated components thereof.

It is known to arrange in flash units or in the viewfinder of a photographic camera a signal element which indicates whether the existing flash light energy was or is adequate for a correctly exposed shot (for example Fed. Ger. Pub.

Sp. 22 03 541).

However it is common to all known apparatuses of this kind that this indication takes place only after a flash exposure or after emission of a test flash. Thus it is possible that scarcely recurring picture subjects may be lost and film stock may be used up unnecessarily.

The technique of picture-taking with flash is to be improved with the invention.

It is the problem of the invention to produce an apparatus for flash photography which increases the quality output of flash exposures and renders superfluous the activation of the flash unit for the emission of a test flash.

In accordance with the invention this problem is solved in that an emission system, independent of the flash emission, for preferably invisible light directed on to the subject and a reception system for a reflected light proportion are provided and in that the output signal of the light reception system, together with signal values characteristic of the guide number of the flash unit, the film sensitivity and the pre-selected diaphragm aperture, is fed to a computer unit which is followed by an indicator for the preliminary indication of expectable incorrect exposure and/or correct flash exposure.

The invention will be explained in greater detail hereinafter by reference to examples of embodiment.

Figure 1 shows an apparatus for flash photography with computer flash unit and integrated additional light emission and reception system, Figure 2 shows an apparatus for flash photography with flash unit of constant light emission and self-focussing camera.

According to Figure 2 a camera 14 comprises having a flash control circuit 1 is additionally provided with a light emission and reception system 3 on infra-red basis (hereinafter called IR system), a computer unit 4 and a linkage circuit 5.

The computer flash unit 2 is in connection through contacts 6, 7, 8 and 6', 7', 8' with a camera circuit 9 consisting inter all of an indicator 10 for the preliminary indication of correct or inadequate flash exposure and an input stage 11 for the processing of an object brightness signal L with guide values signals corresponding to the pre-selected lens diaphragm aperture k and the film sensitivity x. As indicated by an arrow, the input stage is in connection with a circuit (not shown) for exposure time formation.

12 indicates a memory circuit and 13 a releaser catch for the camera.

According to Figure 2 a camera 14 comprises an automatic focussing system 1 5 with active rangefinder system, a computer unit 16, a signal linkage circuit 17 and an indicator 18 for the preliminary indication of expectable correct exposure or flash under-exposure or overexposure. The camera is in connection through contacts 19, 20 with contacts 19', 29' of a flash unit 21 of constant light emission. 22 designates a flash switch.

The manner of operation is as follows Startling from the exposure equation: c.k2.1 0-x/1O L L=subject brightness with the photometric equation for flash lighting: I.p ff 12 I=flash unit light intensity the following equation results for the exposure time t:

constant .12.p-1 For the advance indication of the expectable exposure with computer flash unit (Figure 1 ) the IR system 3 is set in operation. The radiation and reception of infra-red light take place through a common optical system.The proportion of light reflected by the picture subject, which determines the exposure time t, is proportional to the product of 12. pl, thus in desired manner it corresponds to the shooting distance I and the degree of remission p which differs from subject to subject.

In the computer unit 4 a signal is formed from the reflected light proportion by comparison with; signal values characteristic of the guide number of the flash unit, the pre-selected diaphragm aperture k and the film sensitivity x, which signal is fed preferably together with a flash readiness signal CCS to the linkage circuit 5. The output signal of the linkage circuit is fed by way of the contacts 6, 6' to the indicator 10 which is visible in the camera viewfinder and preferably is formed as a single luminous element.

This indicator 10 is stimulated into for example constant lighting (represented symbolically in Figure 1 by the circle sign) when the said output .signal corresponds to an expectable correct flash exposure. In this case a proper exposure can take place in that during the open phase of the shutter the flash ignition takes place through the centre contacts 7', 7. With the lens diaphragm shut down to the preselected aperture value k the subject brightness is ascertained and an appropriate signal is fed through the computer unit 4 to the flash control circuit 1. After entry of a specific quantity of flash light the flash is extinguished and thus the exposure time is determined. In place of the signal taken from the input stage 11 for flash regulation it is also possible to use that of the memory circuit 12 which may be present in the camera.If an underexposure is to be expected (represented symbolically in Figure 1 by the minus sign), the indicator flashes and signals that the range of the shot must be shortened and/or the diaphragm aperture must be opened further. It is not possible to overlook this necessity because the output signal of the memory circuit 12 at the same time activates the releaser catch 13 of the camera. An optical indication of a possible over-exposure is not necessary, by reason of the above-described automatic flash quantity regulation of computer flash units.

According to Figure 2 the automatic focussing system 1 5 on infra-red basis present in the camera is used for the flash pre-indication. The output signal delivered by this likewise contains the product 12. p- which characterises the exposure range and the degree of remission of the subject.A corresponding signal value is fed, together with signal values characteristic of the pre-selected lens diaphragm aperture k, the film sensitivity x and the guide number of the flash unit, to the computer unit 1 6. If the subject brightness is sufficient a signal appears at the output of the computer unit and is processed with a readiness for flash signal fed through the contacts 19', 19, in a linkage circuit 1 7 and activates the flash indicator 1 8 to constant lighting. During the open period of the camera shutter the switch 22 is closed and through the contacts 20, 20' the flash unit 23 of constant light emission is ignited. If the subject brightness is not sufficient, that is if an incorrect exposure is to be expected, the flash indicator is caused to light up intermittently by the computer unit.A lighting sequence of low frequency indicates an under-exposure, a lighting sequence of higher frequency an expectable over-exposure.

Without departing from the scope of the invention the circuit units as represented in the examples of embodiment can also be associated with the flash unit and the camera in a manner other than that illustrated. For example the IR system 3 can be arranged in a camera not equipped for automatic focussing and only the computer unit 4 may be arranged in the flash unit 2. On the other hand it is possible to transmit, out of the output signal delivered by the IR system 3 which contains the information as to the range I of the subject, a corresponding signal directly into the camera, in order to effect the focussing here.

In the latter manner a camera-bound emission and reception system for focussing would be superfluous. In the interest of a flash preindication on the basis of an optional integral or part-integral measurement the working angle of the light emission and reception system is variable. Likewise the infra-red measurement light can be replaced by modulated visible light. In the case of flash units the optical axis of which is pivotable for the purpose of indirect flash illumination, provision is made that the optical axis of the emission system always lies parallel to the first-mentioned optical axis.

Claims

1.) Apparatus for flash photography which comprises an indicator for indicating adequate flash energy for a correct film exposure, characterised in that an emission system independent of the flash emission is provided for preferably invisible light directed on to the picture subject and a reception system (3) is provided for a reflected-back light proportion and in that the output signal of the light reception system is fed, together with signal values characteristic of the guide number of the flash unit, film sensitivity and pre-selected diaphragm aperture, to a computer unit (4) which is followed by an indicator (10) for the preliminary indication of expectable incorrect flash exposure and/or correct flash exposure.

2.) Apparatus according to Claim 1, characterised in that the light emission and reception system of a focussing device (1 5) at the same time forms the light emission and reception system for the actuation of the indicator for the flash exposure preliminary indication.

3.) Apparatus according to Claim 1, characterised in that the flash exposure advance indicator is formed preferably as a single luminous element with different operational conditions for correct and for over and under exposure when using flash units with constant light emission or for under-exposure when using computer flash units.

4.) Apparatus according to Claim 1, characterised in that the indicator is actuated from the linkage of the signal value corresponding to a correct flash exposure with a signal value characteristic of flash readiness.

5.) Apparatus according to Claim 1, characterised in that a storable signal for the light quantity regulation of a computer flash unit is derived at the same time from the signal value for the preliminary indication of correct flash exposure.

6.) Apparatus according to Claim 1, characterised in that a storable signal for the shutter releaser catch (13) is derived from the signal value for the preliminary indication of an incorrect flash exposure.

7.) Apparatus according to Claim 1, characterised in that the working angle of the light emission and reception system is variable for optional integral or part-integral measurement.

8.) Apparatus according to Claim 1, characterised in that the optical axis of the emission system always lies parallel to the pivotable optical axis of the flash unit.

9.) Apparatus according to Claim 1, characterised in that a focussing signal for the camera is derived from the output signal of the light emission and reception system which controls the indicator for the flash exposure advance indication.

10.) Apparatus according to Claims 1 and 4, characterised in that a contact system (6, 7, 8, 6', 7', 8') for the transmission of signals for flash readiness, flash release and flash regulation, in any case present between flash unit and camera, is formed at the same time as channel for the transmission of signals gained in the flash unit for the actuation of the indicator for flash preliminary indication or for the camera focussing.

11.) Apparatus for flash photography substantially as described with reference to Figures 1 and 2 of the accompanying drawings.