GB2141248A

GB2141248A - Film data reading device in a camera

Info

Publication number: GB2141248A
Application number: GB08414396A
Authority: GB
Inventors: Eiichi Tano
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1983-06-07
Filing date: 1984-06-06
Publication date: 1984-12-12
Also published as: DE3421227A1; GB8414396D0; JPS59226330A; GB2141248B

Abstract

A camera includes an exposure control circuit 27, a set of terminals 2a-6a for reading film sensitivity data provided on a record plate attached to a film cartridge 21, a pair of terminals 1a, 7a for reading data on the record plate which indicate the presence or absence of film sensitivity data on the cartridge 21, a detecting unit 24, a manual film sensitivity setting circuit 25, and a selecting circuit 27. When the unit 24 detects that film sensitivity data is present on cartridge 21, data read by terminals 2a to 6a is supplied to the exposure control circuit 27, and when unit 24 detects that sensitivity data is not present data from the setting circuit 25 is supplied to the exposure control circuit 27. <IMAGE>

Description

SPECIFICATION Film data reading device in a camera The present invention relates to cameras having circuitry for detecting data, such as film sensitivity data, encoded on a film cartridge loaded in the camera.

The main cause of unsatisfactory pictures taken with an automatic exposure camera is that the film sensitivity is not correctly set in the camera. For example, even if an exposure value is automatically set, a corrected exposure value cannot be obtained without setting the correct film sensitivity. Recently, Kodak Company has proposed a system in which digital codes, namely, camera automatic sensing codes are used to record film sensitivity (hereinafter referred to as "ISO") on the film cartridge. The recorded data on such a film (hereinafter referred to as "a CAS (camera auto sensing) film") can be read by a film data reading device in the camera. When CAS film is used with a camera having an appropriate reading device, errors caused by improper setting of the film sensitivity can be prevented.

However, both CAS film and non-CAS film are used at various times in the same camera, and therefore it is essential for the operator to properly select between automatic or manual setting of film sensitivity. Improper selection will result in the same problem as previously noted.

It is an object of this invention to provide an improved camera in which the above-mentioned problem is overcome or reduced.

According to this invention, there is provided a camera having an exposure control circuit adapted to receive at an input thereof a film sensitivity value, a manual setting means for manually selecting a film sensitivity value, and a data detector for detecting film sensitivity data recorded on film cartridges which may be inserted in said camera and for providing in response thereto a film sensitivity value, and a data sensing means for sensing the presence of film sensitivity data recorded on a film cartridge loaded in said camera and for causing said film sensitivity value from said detector to be applied at an input of said exposure value circuit when said presence is sensed, and for causing said film sensitivity value from said manual setting means to be applied at an input of said exposure value circuit when said presence is not sensed.

This invention will now be described in more detail, by way of example, with reference to the drawings in which: Figure 1 is a perspective view showing one example of a film with codes automatically sensed by the camera; Figure 2 is a table indicating an example of film sensitivity codes provided on a film; Figure 3 is a block diagram showing one example of a film data reading device embodying this invention.

Figure 4 is a circuit diagram showing the film data reading device in more detail.

Figure 1 is an explanatory diagram showing a CAS film. A record code plate 23 is attached onto the surface of the cartridge 22 of the CAS film 21. The record code plate 23 has record bits 1 through 12.

For convenience in description, the twelve record bits are shown separated from one another by the broken lines.

In order to provide the twelve record bits, an electrically conductive member is divided into twelve blocks, and the blocks are selectively coated with insulating material. Of these record bits, one pair of record bits 1 and 7, the uppermost in Figure 1, form a film identifying section R which designate that this film is a CAS film. The record bits 1 and 7 are electrically conductive. In other words, the record bits 1 and 7 are noting but a conductor. A pair of film identifying terminals la and 7a (Figures 3 and 4) are provided in the camera so that they are brought into contact with the record bits 1 and 7, respectively.

The remaining record bits 2 to 6 and 8 to 12 are selectively coated with insulating material, and form a film data section I in which, for instance, ISO data is recorded. Film data detecting terminals 2a to 6a and 8a to 12a are provided in the camera so that they are brought into contact with the record bits 2 to 6 and 8 to 12 (Figures 3 and 4). In Figure 1, the record bits coated with insulating material are shown in black, representing a high logic level (hereinafter referred to as "H" or ), "'), and the white record bits are not coated with insulating material, representing a low logic level (hereinafter referred to as "L" our "0").

Therefore, film data such as film sensitivity data can be recorded by combination of "H" and "L".

Figure 2 shows a code table in which film sensitivities are represented by five record bits 2 to 6. The film sensitivity indicated by the record code plate in figure 1 is ISO 1000. The record bits 8 to 12 are used to record the number of frames, a latitude, etc.; however, their description will be omitted because they are not directly related to the invention.

Figure 3 is a block diagram showing the fundamental arrangement of the film data reading device according to the invention. The aforementioned film identifying terminals 1a and 7a are provided on a detecting unit 24. ISO data detected by the film data detecting terminals 2a to 6a is applied as 5-bit digital data to an input terminal IN1 of a selecting circuit 26. The selecting circuit 26 has another input terminal IN2 to which a manual film sensitivity setting means 25 applies film sensitivity data. In response to the output of the detecting unit 24, the selecting circuit applies one of the two data outputs to an exposure control circuit 27.

When a CAS film is loaded in the camera, the film identifying terminals 1a and 7a are short-circuited by the record bits 1 and 7 in the film identifying section R. Therefore, the detecting unit 24 detects the presence of the CAS film from the short-circuiting of the terminals and applies the detected data to the control terminal of the selecting circuit 26. Upon reception of the data, the selecting circuit 26 applies, with priority, the ISO data detected by the data detecting terminals 2a to 6a to the exposure control circuit 27 no matter what film sensitivity has been set in the manual setting means 25.

On the other hand, when an ordinary film other than CAS films is loaded in the camera, the film identifying terminals 1 a and 7a are not shortcircuited because the surface of the film cartridge is covered with insulating material. In this case, in response to the detection output of the detecting unit 24, the selecting circuit 26 supplies the film data from the manual setting means 25 to the exposure control circuit 27.

Figure 4 is a circuit diagram showing the film data reading device of the invention in more detail. In Figure 4, those components which have been previously described with reference to Figure 3 are therefore designated by the same reference numerals or characters.

In Figure 4, reference numeral 28 designates a camera body, in which the exposure control circuit 27 is provided. The voltage of a battery 29 is applied through a photometering switch 30 to the exposure control circuit 27. The "on" and "off" conditions of switches S2 to S6 drawn between the record bits 2 to 6 and the record bits 1 and 7 indicate whether or not the record bits 2 to 6 are coated with insulating material.

The manual film sensitivity setting means 25 comprises switches MS2 to MS6, equivalent to the switches S2 to S6. When an ISO value is manually set, these switches are turned on and off according to the ISO value thus set. First terminals of these switches MS2 to MS6 are connected to the collector of an NPN transistorT1 in the detecting unit 24, and the remaining second terminals are connected respectively through diodes D2 to D6 to the data detecting terminals 2a to 6a, and to the exposure control circuit 27. The emitter of the transistor T1 is connected to the detecting terminal 7a and to the negative terminal of the battery 29. The base of the transistorT1 is connected through a resistor R1 to the photometering switch 30 and to the detecting terminal 1a.

The operation of the device thus organised will be described.

Let us consider the case where an ordinary film other than CAS films is loaded in the camera. The non-CAS film may be regarded as the CAS film whose record bits 1 to 12 are coated with insulating material. Under this condition, the record bits 1 and 7 are electrically disconnected from the record bits 2 to 6. When the switch 30 is closed, transistor T1 is rendered conductive, as a result of which the "on" and "off"states of the switches MS2 to MS6 in the manual setting means 25 are applied to the exposure control circuit 27. In this case, the data of the opened switch causes no problem because it is logically "1"; however, there remains some problems as to whether or not the data of the closed switch is logically "0" because of the inputting of the sum of the saturation voltage of the transistor T1 and the diode forward voltage. The sum is generally of the order of 0.7 volt.Therefore, as for the logical level of the exposure control circuits 27 operated on a supply voltage of three to six volts, the data can be regarded as "0" when a suitable threshold value is set.

Therefore, the open states of the switches MS2 to MS6 can be applied as "1" to the exposure control circuit 27, and the closed states as "0".

Now, the case where a CAS film is loaded in the camera will be described. In this case, the base and the emitter of the transistor T1 are short-circuited by the record bits 1 and 7 of the CAS film through the identifying terminals 1 a and 7a, so that the transistor T1 is rendered nonconductive. The "on" and "off" data of the switches MS2 to MS6 are applied through the diodes D2 to D6 to the exposure control circuit 27. Therefore, the diodes D2 to D6, and the switches MS2 to MS6 can be regarded as eliminated when viewed from the exposure control circuit 27.Therefore, when a CAS film is loaded in the camera, the film data represented by the "on" and "off" states of the switches S2 to S6 (expressed "0" and "1", respectively) is inputted to the exposure control circuit 27 completely, irrespective of the "on" and "off" states of the switches MS2 to MS6 in the manual setting means 25.

As is clear from the above description, in the data reading device the detecting unit detects whether or not ISO data is recorded on the film, and according to the result of detection, the film sensitivity data set by the manual setting means orthe film sensitivity data detected by the automatic reading means is selectively applied to the exposure control circuit.

Therefore, the employment ofthefilm data reading device of the invention can positively prevent the trouble that, as CAS films and non-CAS films are available in combination, an error is made in setting a film sensitivity, resulting in a poor picture.

Claims

1. A camera having an exposure control circuit adapted to receive at an input thereof a film sensitivity value, a manual setting means for manually selecting a film sensitivity value, and a data detector for detecting film sensitivity data recorded on film cartridges which may be inserted in said camera and for providing in response thereto a film sensitivity value, and a data sensing means for sensing the presence of film sensitivity data recorded on a film cartridge loaded in said camera and for causing said film sensitivity value from said detector to be applied at an input of said exposure value circuit when said presence is sensed, and for causing said film sensitivity value from said manual setting means to be applied at an input of said exposure value circuit when said presence is not sensed.

2. A camera as claimed in claim 1, in which film cartridges having data readable by said camera include a film identifying section of electrically conductive material and a data section which is encoded by a pattern of the presence and absence of electrically conductive material, and in which said data sensing means comprises a pair of film identifying terminals adapted to contact at their probe ends separate points of said film identifying section, the short circuiting of said probes being sensed as the presence of film sensitivity data.

3. A camera as claimed in claim 2 in which said data detector comprises a plurality of probes adapted to contact different data points in said data section of said recorded data, said data detector having an output signal representing the film sensitivity value recorded in said data section and said output signal being connected to said exposure control circuit, and in which the manual setting means provides an output signal representing said manually set film sensitivity value, the latter output being connected to said exposure control circuit, and in which said data sensing means further comprises a transistor circuit connected to a pair of film identifying terminals and to said manual setting means for deactivating the output from said manual setting means when said probes of said terminals are short-circuited.

4. A camera substantially as hereinbefore described with reference and as shown in the accompanying drawings.