DE2649895A1 - Photoresistor trigger for cine camera film drive - uses shutter blade to control light striking photoresistor and balance comparator circuit preventing exposure when light level is too low - Google Patents

Abstract

The cine camera motor is switched by the shutter blade so that film is not used when light levels are unsuitable. Light striking a photoresistor causes an imbalance in a comparator circuit controlling the shutter blade drive motor. The shutter blade is driven to control the light striking the photoresistor and balance the comparator circuit but, as a determinable light level, an abutment on the blade opens a switch to disconnect the circuit to the film transport motor. Reconnection of the film drive motor circuit follows automatically.

Description

Fade-in and fade-out device for cinematographic cameras

The invention relates to a fade-in and fade-out device for cinematographic Cameras with a film drive that can be actuated by a release device and with a device for regulating the aperture stop containing a light-sensitive Signal value transmitter, a comparison signal value transmitter, a comparison and control device and an aperture stop adjusting motor.

The invention is based on the object of a fade-in and fade-out device To create of the type mentioned, in the case of the film drive motor after dimming has taken place should be shut down to avoid unnecessary film consumption.

The object is achieved according to the invention in that after detuning of the light-sensitive signal value transmitter means a dimmer switch a switch to stop the film drive motor by means of the aperture diaphragm at Reaching their dimmed position is operated, with the shutdown switch with is in series with the trigger switch. When the blind position is reached, without unnecessary film consumption, the drive motor for film transport is shut down. Here it does not matter within which time span the dimming takes place.

Either a direct current motor is used as the aperture diaphragm drive motor or a stepper motor is used.

These motors have the advantage that their torque during the entire fade-out or fade-in process is constant, since the comparison and control device expediently has a digital signal at the output. Thus, when the dimming switch on the dimming shutter is operated, the shutdown switch is activated operated with sufficient force. Appropriately, the switch is by means of a on the aperture provided approach can be actuated.

In the following, the invention is illustrated by means of one in the figure Embodiment described.

According to the figure, 1 denotes a battery that has a Operating switch 2 can be connected to the circuit arrangement. In the input circuit a control circuit 3 is a trigger switch 4, which is normally with a closed switch 5 is connected in series. In the output circuit of the control circuit 3 is a relay e, whose contact 7 is in the circuit of a film drive motor 8 is arranged. One still in the circuit of the film drive motor 8 Circuit arrangement 9 is used for speed control.

Behind an aperture stop 10 there is a photo resistor 11, together with a series resistor 12 as a light-sensitive signal value transmitter serves. Two further resistors 13 and 14 serve as comparison signal value transmitters. An analog comparison circuit is denoted by 15. It is on the output side with connected to an analog-to-digital converter 16, one output of which has a connection with a pulse generator 17 and its other output with a control circuit 18 for a stepper motor 19 is connected. The one with the pulse generator 17 The connected output signals are used to switch the stepper motor on and off 19, while the signals appearing at the other output direction signals for the Stepper motor 19 are. Four excitation windings of the stepper motor are at 20.21 22.23 designated. The armature of the stepping motor is denoted by 24.

From the armature 24 leads a connection to a screw 25, which over a gear 26 is connected to a pin-and-slot connection 27, 28 of the aperture stop 10 is. One approach to the aperture stop 10 is denoted by 29.

The photoresistor is for the purpose of dimming by means of a dimming switch 30 can be bridged.

If dimming is to be carried out, switch 30 is closed and the stepper motor switched on in the sense of a dimming. The aperture diaphragm is closed and when the end position of the aperture diaphragm is reached, the switch 5 opened by means of the approach 29. As a result, even when the trigger switch is closed 4 the control circuit for the relay 6 is interrupted and the film drive motor 8 shut down.

If a fade-in is to take place afterwards, first the switch 30 is open, so that due to the reversed polarity of the detuning the bridge circuit of the stepping motor 19 an opposite direction signal receives and thus the aperture diaphragm 10 opens. As a result, then the switch 5 closed and when the trigger switch 4 is actuated, the relay 6 is energized and The motor circuit for the drive motor 8 is closed via its contact 7.

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Claims (2)

Claims 1. Fade-in and fade-out device for cinematographic cameras with a film drive that can be actuated by a release device and with a Device for regulating the aperture diaphragm containing a light-sensitive signal transmitter, a comparison signal generator, a digital comparison and control device and an aperture diaphragm drive motor, characterized in that after detuning the light-sensitive signal value transmitter by means of a dimming switch a switch (5) to stop the film drive motor (8) by means of the aperture diaphragm when it is reached its dimmed position is actuated, the switch (5) with the trigger switch (4) is in series. 2. Fade-in and fade-out device according to claim 1, characterized in that that the switch (5) by means of an approach provided on the aperture diaphragm (10) (29) can be actuated.