WO2020242358A1

WO2020242358A1 - A computer implemented method and a system for coordinating events in portable electronic camera devices

Info

Publication number: WO2020242358A1
Application number: PCT/SE2020/050341
Authority: WO
Inventors: Tobias LINDBÄCK; Anton Falk
Original assignee: Profoto Aktiebolag
Priority date: 2019-05-27
Filing date: 2020-04-01
Publication date: 2020-12-03

Abstract

The present disclosure relates to a computer implemented method and system for coordinating a primary event in a first portable electronic camera device (101) and at least one secondary event in at least one remote portable electronic camera device (102b, 102c, 102d), wherein the primary event and/or at least one secondary event is an image capture. The method comprises the steps of obtaining (S1) a primary time base for a processor element (105) of the first portable electronic camera device (101), estimating (S2) a respective secondary time base for a processor element (105) of each remote portable electronic camera device (102b, 102c, 102d), scheduling (S3) a timing for initiation of the at least one secondary event in the primary time base, and obtaining (S4) at the remote portable electronic camera device (102b, 102c, 102d) the respective scheduled timing of initiation of the secondary event.

Description

A COMPUTER IMPLEMENTED METHOD AND A SYSTEM FOR COORDI NATI NG EVENTS I N

PORTABLE ELECTRONIC CAMERA DEVICES

TECHN ICAL FI ELD

The present invention relates to photography and in particular to the illumination of a scene during image capture.

BACKGROUND

I n situations when it is desired to provide additional illumination of a scene to be

photographed, a n illumination device may be used to provide additional light. The camera used for image capture may be arranged to provide a sync signal to the illumination device to activate the illumination device when the photographer takes a picture.

SUMMARY

An object of the invention is to improve control in illuminating a scene during image capture of said scene using a portable electronic camera device.

This object has been achieved by means of a computer-implemented method for coordinating initiation of a primary event in a first portable electronic camera device having an image sensor and possibly an illumination device configured to emit a flash, and at least one secondary event in at least one remote portable electronic camera device having an image sensor and possibly an illumination device configured to emit a flash. The primary event and/or at least one secondary event is an image capture with the respective image sensor. The method comprises the steps of obtaining a primary time base for a processor element of the first portable electronic camera device, estimating a respective secondary time base for a processor element of each remote portable electronic camera device in relation to the primary time base. The method further comprises scheduling a timing for initiation of the at least one secondary event in the primary time base so that coordination of the timing for initiation of the primary event and the timing for initiation of each secondary event is obtained, and obtaining at the remote portable electronic camera device the respective scheduled timing of initiation of the secondary event in the respective secondary time base of that portable electronic camera device.

The flash is a brief, sudden burst of light. The flash has characteristically a short extension in time, typically shorter than a second. The use of a flash is less intrusive compared to illuminating with a constant light. Also, a flash allows energy efficient illumination with bright light as it only illuminates during a short time.

In this patent application it is to be understood that the first portable electronic camera device may be any of a digital camera, a camera phone or a tablet, and that the remote portable electronic camera device may be any of a digital camera, a camera phone or a tablet.

In accordance with this method, image capture with an image sensor is coordinated with obtaining of a flash pulse with one or more illumination devices. The coordination may be made such that the at least one flash pulse is emitted at substantially the same point in time or near the same point in time as the image sensor captures or initiates capture of the image. Alternatively, the coordination may be made such that there is a predetermined relation between image capture and the obtaining of the flash pulse of the respective illumination device.

Thereby, the timing of initiation of each secondary event may be coordinated with the primary event between the secondary event from each at least one illumination device and the image capture using the image sensor. The coordination of the timing of initiation of the secondary events and the timing of initiation of the primary event may involve determining timings for the primary event and timings for initiation of the respective secondary events.

With the coordination as defined above, the timing of the secondary events in relation to the primary event may be coordinated so that the at least one flash occurs at a desired timing in relation to the image capture. Further, when a plurality of illumination devices are used, they may be coordinated to flash at a desired timing in relation to each other and in relation to the image capture. Further, when a plurality of image sensors are used, they may be coordinated to capture an image at a desired timing in relation to each other and in relation to flashing my means of the illumination device(s).

According to the method a timing for initiation of the at least one secondary event in the primary time base is scheduled. The timing for initiation of the at least one secondary event is timed with the primary event. Thus, according to an embodiment the timing of the primary event may also be scheduled in the method. It is however not always necessary to schedule the primary event. In some applications it is not possible to schedule the primary event without changing the hardware. One example is mobile phones in which the exact timing of the capture of an image often cannot be controlled with an application. It is however possible to determine the timing when the mobile phone will capture the image after an initiation of an image capture by, e.g., pushing a button on the mobile phone. In such a case it is known that the image will be captured at a predetermined point in time. It is then only the secondary event that has to be scheduled. Another example of when the method does not have to include the scheduling of the primary event is when the scheduling is performed after the steps in the method. Thus, the scheduling of the primary event may be performed after obtaining at the remote portable electronic camera device the respective scheduled timing of initiation of the secondary event in the respective secondary time base of that portable electronic camera device.

It is of course possible to have more than one secondary event in the same remote portable electronic camera device. It is for example possible to emit a flash and capture an image with the same remote portable electronic camera device.

It is of course possible to have more than one primary event in the first portable electronic camera device. It is for example possible to emit a flash and capture an image with the first portable electronic camera device. It is for example possible to emit a flash and capture an image as primary events in the first portable electronic camera device.

The coordination of the timing for emission of the flashes in relation to the image capture so that the at least one flash occurs at a desired timing in relation to the image capture has the effect that the amount of artificial light provided to the captured scene can be increased, for example in relation to if an artificial light having a constantly emitting light is used. The avoidance of a constantly emitting light is also advantageous for other reasons. For example, the constantly emitting light may be disturbing.

Further, the amount of artificial light can be adjusted, manually or automatically. The amount of light may be adjusted in relation to the ambient light and/or, if a plurality of portable electronic camera devices with illumination devices are used, between the illumination devices of the different portable electronic camera devices.

The method as disclosed herein allows for coordination of flashes of the illumination devices of portable electronic camera devices with the image capture, but also external illumination devices may be added to the set-up and coordinated in the same manner as the illumination devices of the portable electronic camera devices.

The time base for a portable electronic camera device should be understood herein as the time base for a processor element of said device.

Characteristically the primary time base of the first portable electronic camera device and the secondary time base of the at least one remote portable electronic camera device are different. Thus, a clock of a processor element of the first portable electronic camera device has characteristically a different timing than a clock of the respective remote portable electronic camera device. This instantaneous difference between the readings of the clock of the first portable electronic camera device and the respective remote portable electronic camera device is called their skew or clock skew. Thus, there is characteristically a skew between the primary time base of the first portable electronic camera device and the respective secondary time base of the at least one remote portable electronic camera device. Thus, the skew may be taken into account when coordinating timing of initiation of flashes from each of the one or more illumination devices and the image capture using the image sensor.

Further, the time bases may drift in relation to each other with time. Therefore, the estimation of the secondary time base for a processor element of each at least one remote portable electronic camera device in relation to the primary time base of the processor element of the first portable electronic camera device may be performed continuously or repeatedly. The primary event may be an image capture with the image sensor of the first portable electronic camera device. Such a primary event may be combined with any secondary event. It is also possible to coordinate a plurality of secondary events in a plurality of remote portable electronic camera devices. The secondary event may be different in different remote portable electronic camera devices. Thus one remote portable electronic camera device may capture an image with the image sensor of the respective remote portable electronic camera device as secondary event, while another remote portable electronic camera device may emit a flash with an illumination device of the respective remote portable electronic camera device as secondary event.

The primary event may be an emission of a flash with the illumination device of the first portable electronic camera device. With such a primary event at least one remote portable electronic camera device must capture an image as the secondary event.

The step of estimating a respective secondary time base for a processor element of each remote portable electronic camera device in relation to the primary time base may comprise the steps of transmitting at least one request for time information relating to the remote portable electronic camera device, obtaining a timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device, obtaining a response for each remote portable electronic camera device comprising the requested time information in a time base of that remote portable electronic camera device, and determining the estimate of the respective secondary time base for the processor element of each at least one remote portable electronic camera device in relation to the primary time base based on the obtained timing of the transmission of the request for time information and the time information comprised in the response for the respective remote portable electronic camera device.

The timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device that is obtained may either be stored in the first portable electronic camera device or be transmitted with the request to the remote portable electronic camera devices. In the latter case the obtained time reference of the first portable electronic camera device must be sent back in the response for each remote portable electronic camera. The obtained response for each remote portable electronic camera device comprises the requested time information in a time base of that remote portable electronic camera device. Depending on whether the timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device was sent to the remote portable electronic camera device or not the requested time information may have different formats. In case the timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device was not sent to the remote portable electronic camera device the requested time information is the time of the reception of the request in the time base of that remote portable electronic camera device. In case the timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device was sent to the remote portable electronic camera device the requested time information may either be the time of the reception of the request in the time base of that remote portable electronic camera device or the difference between the timing of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device and the time of the reception of the request in the time base of that remote portable electronic camera device. Thus, the requested timing is expressed as a positive or negative difference.

The present disclosure further relates to a control system for coordinating initiation of at least a primary event and at least one secondary event in a plurality of portable electronic camera devices, each having an image sensor to capture an image and possibly an illumination device configured to emit a flash. The control system is arranged to control the initiation of the primary event in a first portable electronic camera device among the plurality of portable electronic camera devices, said first portable electronic camera device having a processor element operating in a primary time base, and the initiation of the at least one secondary event in at least one remote portable electronic camera device among the plurality of portable electronic camera devices, each remote portable electronic camera device having a processor element operating in a respective secondary time base. The primary event and/or at least one secondary event is an image capture with the respective image sensor. The control system comprises a time base estimating element arranged to estimate a relation between the primary and the respective secondary time bases, a scheduler element, arranged in one of the portable electronic camera devices, and arranged to schedule in the primary time base a timing for initiation of said at least one secondary event so that coordination of the timing for initiation of the primary event and timing for initiation of said at least one secondary event is obtained, and a communication interface arranged to transmit to the respective remote portable electronic camera device the scheduled timing for initiation of the secondary event of that remote portable electronic camera device.

The discussion above regarding the possible scheduling of the primary event is valid also for the control system.

The present disclosure further relates to a portable electronic camera device arranged to coordinate initiation of a primary event in said portable electronic camera device and initiation of at least one secondary event in at least one remote portable electronic camera device, wherein the portable electronic camera device comprises an image sensor, possibly an illumination device, and a processor element operating in a primary time base, wherein the remote portable electronic camera device comprises an image sensor, possibly an illumination device, and a processor element operating in a respective secondary time base, and wherein the primary event and/or at least one secondary event is an image capture with the respective image sensor. The portable electronic camera device comprises at least a part of a time base estimating element arranged to estimate a relation between the primary and the respective secondary time bases, a scheduler element arranged to schedule in the primary time base a timing for initiation of the at least one secondary event in the respective remote portable electronic camera device so that coordination of the timing for initiation of the primary event and the timing for initiation of said at least one secondary event is obtained, and a

communication interface arranged to transmit to the respective remote portable electronic camera device the scheduled timing of said remote portable electronic camera device.

As stated above the first portable electronic camera device may be any of a digital camera, a camera phone or a tablet, and the remote portable electronic camera device may also be any of a digital camera, a camera phone or a tablet.

The discussion above regarding the possible scheduling of the primary event is valid also for the portable electronic camera device. The primary event may be an image capture with the image sensor of the portable electronic camera device. Such a primary event may be combined with any secondary event. It is also possible to coordinate a plurality of secondary events in a plurality of remote portable electronic camera devices. The secondary event may be different in different remote portable electronic camera devices. Thus one remote portable electronic camera device may capture an image with the image sensor of the respective remote portable electronic camera device as secondary event, while another remote portable electronic camera device may emit a flash with an illumination device of the respective remote portable electronic camera device as secondary event.

The first portable electronic camera device may be arranged to communicate with the at least one remote portable electronic camera device via a Bluetooth interface.

The present disclosure further relates to a computer program product for performing the method for coordinating initiation of a flash pulse of at least one portable electronic camera device and image capture using an image sensor of a portable electronic camera device, as disclosed herein.

The discussion above regarding the possible scheduling of the primary event is valid also for the computer program product.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a scheme illustrating an example of a system for coordinating initiation of a first event in a first portable electronic camera device having an image sensor and possibly an illumination device configured to emit a flash, and at least one secondary event in at least one remote portable electronic camera device having an image sensor and possibly an illumination device configured to emit a flash. Figure 2a illustrates an example of a back side of a portable electronic camera device.

Figure 2b illustrates an example of a front side of a portable electronic camera device.

Figure 2c illustrates an example of a portable electronic camera device in the form of a digital camera.

Figure 2d illustrates an example of a portable electronic camera device in the form of a digital camera.

Figure 3 is a scheme illustrating an example of a control system for coordinating a plurality of portable electronic camera devices to capture at least one image and initiate at least one flash.

Figures 4a and 4b is a scheme schematically illustrating some aspects of the control system of figure 3.

Figure 5 is a flow chart illustrating an example of a computer-implemented method for coordinating initiation of a flash pulse of at least one illumination device and image capture using an image sensor.

Figure 6 is a flow chart illustrating an example of the step in figure 5 of estimating a time base for each at least one remote portable electronic camera device relative to an obtained time base of the first portable electronic camera device.

Figure 7 is a time scheme illustrating a detailed example of a step for estimating a time base for a remote portable electronic camera device relative to a time base for a first portable electronic camera device.

Figure 8 is a time scheme illustrating a modified detailed example of a step of estimating a time base for a remote portable electronic camera device relative to a time base for a first portable electronic camera device. DETAILED DESCRIPTION

In figure 1 an example of a system 100 for coordinating initiation of a primary event and at least one secondary event is illustrated.

In figure 1, the system 100 comprises a first portable electronic camera device 101 and a first, a second, and a third remote portable electronic camera device 102b, 102c, and 102d. The first portable electronic camera device 101 is a digital camera, a camera phone or a tablet. The first portable electronic camera device comprises an image sensor 61a and an illumination device 62a.

The remote portable electronic camera devices 102b, 102c, 102d, in Fig. 1 are digital cameras, camera phones or tablets The different remote portable electronic camera devices 102b,

102c, 102d do not have to be the same, but may be independently chosen from a digital camera, a camera phone and a tablet. The remote devices 102b, 102c, and 102d, comprise an image sensor 61b, 61c, 61d, and an illumination device 62b, 62c, 62d, except for the third remote portable electronic camera device 102d which comprises an image sensor 61d but no illumination device.

Each device of the system 100 has a control element (not shown) for controlling that device. Each control element is associated to an internal clock 104a, 104b, 104c, 104d of the corresponding device. The internal clock 104a, 104b, 104c, 104d provides a time base for that device. Each device is controlled by the corresponding control element and the control element operates in the time base of that device.

Figure 2a illustrates an example of a portable electronic camera device 101 or a remote portable electronic camera device 102b-102d, which in the illustrated example is a smart phone with an image sensor 61 and a lens 64, and an illumination device 62 configured to emit a flash are positioned on a back side of a portable electronic camera device. Further, an additional image sensor and at least one illumination device configured to emit a flash may be positioned on a front side of the portable electronic camera device 101 or the remote portable electronic camera device 102b-102d.

In figure 2b, an example is illustrated wherein the image sensor 61 and illumination device 62 configured to emit a flash are positioned on a front side of the portable electronic camera device 101 or the remote portable electronic camera device 102b-102d. Further, an additional image sensor and at least one an illumination device configured to emit a flash may be positioned on a back side of the portable electronic camera device 101.

Figure 2c illustrates an example of a portable electronic camera device 101 or a remote portable electronic camera device 102b-102d, which in the illustrated example is a digital camera with an image sensor 61, a lens 64, and an illumination device 62 configured to emit a flash.

Figure 2d illustrates an example of a portable electronic camera device 101 or a remote portable electronic camera device 102b-102d, which in the illustrated example is a digital camera with an image sensor 61, and a lens 64.

In the system 100 illustrated in Fig. 1 the portable electronic camera devices do not have to be of the same type, but may be any combination of camera phones, digital cameras, and/or tablets.

Further, in the illustrated example an application 65 is loaded into the portable electronic camera device 101. The app is configured to coordinate initiation of a primary event being the emission of a flash from an illumination device 62 in a portable electronic camera device 101 and initiation of a secondary event being image capture using the image sensor 61 of a remote portable electronic camera device 102b-102d, as disclosed herein. The app 65 may comprise a user interface for user input. The user input may for example be user input for initiating capture of an image. The user input may be adapted for clustering together portable electronic camera devices and possible additional illumination devices clustered for coordination of image capture and emitting flash pulses using said clustered devices. The user interface may also be used for user input of user preferences. For example the user preferences may comprise relation between amount of ambient light and artificial light and/or a relation between amount of light in the flashes from the different illumination devices.

As an alternative the application may be configured to coordinate initiation of a primary event being the capture of an image using the image sensor 61 of a first portable electronic camera device 101 and initiation of a secondary event being the capture of an image using the image sensor 61 of a remote portable electronic camera device. It is possible to add additional portable electronic camera devices 102b-102d and to coordinate a plurality of secondary events. The secondary events may be different in different remote portable electronic camera devices 102b-102d. Thus, one secondary event may be the initiation of the imaged capture with the image sensor 61 of a remote portable electronic camera device 102 while another secondary event may be the initiation of the emission of a flash from the illumination device 62 of another remote portable electronic camera device 102b-102d.

It is of course also possible to coordinate two secondary events in the same remote portable electronic camera device 102b-102d, i.e., a remote portable electronic camera device 102 may be controlled to capture an image as well as emitting a flash, while the first portable electronic camera device 101 is controlled to, e.g., capture an image.

Figure 3 illustrates a control system 200 for coordinating a plurality of portable electronic camera devices to capture at least one image and initiate at least one flash. The control system is implemented in a system comprising the plurality of portable electronic camera devices. The plurality of portable electronic camera devices having each an image sensor to capture an image and an illumination device configured to emit a flash. The plurality of portable electronic camera devices comprise a first portable electronic camera device and at least one remote portable electronic camera device. For example, the control system may be implemented in a system having at least some devices as discussed in relation to figure 1. For example, the elements of the control system 200 may be mainly or in part implemented in a first portable electronic camera device, as discussed in relation to figure 1.

The control system 200 is arranged to control operation of the first portable electronic camera device among the plurality of portable electronic camera devices and at least one remote portable electronic camera device among the plurality of portable electronic camera devices. The first portable electronic camera device has a processor element 105 operating in a primary time base. Each remote portable electronic camera device has a processor element 105 operating in a respective secondary time base.

The control system 200 comprises a scheduler element 210 and a time base estimating element 211. The scheduler element and the time base estimating element are essentially arranged in one of the portable electronic camera devices or shared between the portable electronic camera devices. The scheduler element is characteristically comprised in the first portable electronic camera device. The time base estimating element is shared between the first portable electronic camera device and the remote portable electronic camera device. This will be described in more detail in relation to figures 4a, 4b.

The control system 200 further comprises a communication interface(s) 212 for

communication between different devices of the system.

The control system 200 may further comprise a user interface 213 for receiving user requests. The user interface comprises means for receiving a user request to capture an image. The user interface may therefore for example comprise an image sensor pushbutton. The push button may be a physical pushbutton arranged at the portable electronic camera device. The user interface may comprise a touchscreen of the portable electronic camera device.

The scheduler element 210 is arranged to, upon request, schedule a timing for initiation of a flash pulse of at least one of the illumination devices and/or a timing for image capture using the at least one image sensor in the time base of the first portable electronic camera device so that the timing(s) for capturing the image(s) is coordinated with the timing(s) for initiating the at least one flash.

The request is characteristically obtained via the "image sensor pushbutton "of the user interface 213.

The scheduled timing(s) are fed from the scheduler element 210 to the devices of the system 100. The scheduled timing(s) for those devices, which are remote portable electronic camera devices, are fed to the communication interface 212 for transmission of the scheduled timings to the respective remote portable electronic camera device. Any scheduled timing associated to a flash or image capture event in the device in which the scheduler element is implemented is also communicated to that illumination device or image sensor.

The scheduled timing(s) fed to the communication interface 212 is/are transmitted to the remote portable electronic camera device to which the particular timing for initiation of a flash pulse and/or for initiation of image capture is associated.

The time base estimating element 211 is arranged to obtain a time base for a processor element 105 of the own device 101 and estimating a time base for each at least one remote portable electronic camera device 102 relative to the obtained time base of the own device 101. Generally, the estimation of time base comprises transmitting at least one request for time information relating to said at least one remote portable electronic camera device, obtaining a timing of the transmission of the request for time information based on the obtained time reference, receiving a response from each said at least one remote portable electronic camera device comprising the requested time information in a time base of that remote portable electronic camera device, and determining the estimate of the time base for each at least one remote portable electronic camera device based on the obtained timing of the transmission of the request for time information and the time information comprised in the response from respective remote portable electronic camera device. Examples of how the time bases may be estimated will be discussed in more detail below.

Figures 4 a, b disclose an aspect of the control systems 200 for coordinating a plurality of portable electronic camera devices to capture at least one image and initiate at least one flash, as exemplified in figure 3. The control system is arranged to control operation of a first portable electronic camera device 101 having a processor element 105 operating in a primary time base and at least one remote portable electronic camera device 102 having a processor element 105 operating in a respective secondary time base.

The first portable electronic camera device 101 may be a digital camera, a camera phone or a tablet.

The at least one remote portable electronic camera device 102 may comprise at least one remote illumination device. The at least one remote portable electronic camera device may comprise a camera phone or a tablet.

The control system 200 comprises a time base estimating element 211 arranged to estimate a relation between the primary and the respective secondary time bases. The control system comprises further a scheduler element 210 arranged to schedule in the time base of the first portable electronic camera device a timing for initiation of the secondary event, being a flash pulse of the at least one illumination device and/or a an image capture using the at least one image sensor, whereby the timing for initiation of the secondary event is coordinated with the timing for initiation of the primary event, being an image capture or an emission of a flash.

The primary event and/or at least one secondary event is an image capture with the respective image sensor Communication between the first portable electronic camera device and the at least one remote portable electronic camera device is performed over a communication interface (not shown). The communication interface may be a wireless interface such as a Bluetooth interface.

In the example of figure 4a, the time base estimating element 211 is arranged to transmit from the first portable electronic camera device to the at least one remote portable electronic camera device at least one request TR over said communication interface. The request is a request for timing information relating to said at least one remote portable electronic camera device. The request may comprise an identity uniquely identifying the request. Further, the time base estimating element is at the first portable electronic camera device arranged to obtain a timing (TTRI, T TR2, T TR3) of the transmission of the request for time information in the obtained primary time base.

In response to receiving the transmission request TR, the remote portable electronic camera device is arranged to provide the requested time information in the secondary time base of that remote portable electronic camera device. The time base estimating element is at the remote portable electronic camera device further arranged to form a response (R) comprising the requested time information and to transmit the formed response to the first portable electronic camera device. The response comprises characteristically also the identity uniquely identifying the request. Thereby, pairing of the request with its corresponding response is facilitated.

A time base determining part 214 of the time base estimating element is arranged to determine the estimate of the secondary time base for the processor element 105 of each at least one remote portable electronic camera device in relation to the primary time base of the processor element 105 of the first portable electronic camera device based on the obtained timing of the transmission of the request for time information and the time information comprised in the response (R) from the respective remote portable electronic camera device.

The scheduler element 210 is arranged to feed to the communication interface for further communication to the respective remote portable electronic camera device the scheduled timing for the respective remote portable electronic camera device in the secondary time base. In the example of figure 4b, the time base estimating element 211 is arranged to transmit from the first portable electronic camera device to the at least one remote portable electronic camera device at least one transmission request TR over said communication interface. The transmission request is a request for timing information relating to said at least one remote portable electronic camera device. Further, the time base estimating element 211 is at the first portable electronic camera device 101 arranged to obtain a timing of the transmission of the request for time information in the obtained primary time base and to include the obtained timing of the transmission of the request in the request.

In response to receipt of the transmission request TR, the remote portable electronic camera device is arranged to obtain the requested time information in the secondary time base of that remote portable electronic camera device.

The time base determining part 214 of the time base estimating element is in this example arranged at the respective remote portable electronic camera device 102. The time base determining part is arranged to determine the estimate of the secondary time base for the processor element 105 of its remote portable electronic camera device in relation to the time primary base of the processor element 105 of the first portable electronic camera device based on the obtained timing of the transmission of the request for time information and the obtained requested time information.

The scheduler element 210 is arranged to feed to the communication interface the scheduled timing for the respective remote portable electronic camera device in the primary time base, for further communication to the respective remote portable electronic camera device. The respective remote portable electronic camera device may then convert the scheduled timing to a timing in the secondary time base of that remote portable electronic camera device.

In figure 5, an example of a computer implemented method 10 for coordinating initiation of a primary event in a first portable electronic camera device and initiation of a secondary event in a remote portable electronic camera device is illustrated.

The method is adapted for a system including a first portable electronic camera device having an image sensor and a illumination device, and at least one remote portable electronic camera device having an image sensor and a illumination device. The method comprises the steps of obtaining SI a primary time base for a processor element 105 of the first portable electronic camera device.

The method further comprises a step of estimating S2 a respective secondary time base for a processor element 105 of each at least one remote portable electronic camera device in relation to the primary time base.

The communication between the first portable electronic camera device and at least one remote portable electronic camera device may be performed over a wireless channel with predetermined communication timings, so called connect events. The estimation S2 of a secondary time base for each at least one remote portable electronic camera device is then performed also based on the predetermined communication timings. Further, the primary and respective secondary time bases may drift in relation to each other with time. Therefore, the estimation S2 of the secondary time base for a processor element 105 of each at least one remote portable electronic camera device in relation to the primary time may be performed continuously or repeatedly.

The method further comprises a step of scheduling S3 a timing for initiation of a secondary event, being the initiation of the flash from the illumination device and/or the initiation of an image capture using the image sensor of the at least one remote portable electronic camera device, in the primary time base so that coordination of the timing for initiation of the first event and the timing for initiation of the second event is obtained. The scheduling may be performed at least in part in the first portable electronic camera device. The scheduling characteristically takes place when the user indicates a wish to capture an image via a user interface at the first portable electronic camera device. The indication may in another example be obtained by means of an indication via a user interface of one of the remote portable electronic camera device(s). The scheduling may take into account any delays within the respective devices to initiate image capture and/or initiating the flash light. The scheduling may also or instead take into account timings of connect events for communication between the first portable electronic camera device and the respective remote portable electronic camera device. The timings for connect events may be provided in the step of estimating S2 the time base for the respective remote portable electronic camera device; this is further illustrated in relation to figures 7 and 8. The scheduling may comprise obtaining a timing for scheduling initiation of a primary event, being the initiation of a flash and/or initiation of image capture, of the first portable electronic camera device itself. The timing for scheduling of the first portable electronic camera device is then fed to hardware/software for control of initiation of a flash and/or initiation of image capture by means of the first portable electronic camera device. The scheduling of a primary event may be omitted in case it is not possible to control the timing of the primary event. It might be that when the user indicates a wish to capture an image via a user interface at the first portable electronic camera device an image is captured after a predetermined delay. It is then only the secondary event(s) that have to be scheduled to occur at the same time as the first event.

The method further comprises a step of obtaining S4 at the respective remote portable electronic camera device of the system the scheduled timing for initiating the secondary event, being initiation of the flash and/or initiation of the image capture by means of the remote portable electronic camera device in the secondary time base of that device. The scheduled timing is communicated from the first portable electronic camera device to the respective remote portable electronic camera device.

In figure 6, an example of a step of estimating S2 a secondary time base for a processor element 105 of each at least one remote portable electronic camera device in relation to the primary time base of the processor element 105 of the first portable electronic camera device of a computer implemented method as discussed in relation to figure 5 is disclosed. In the illustrated example, the step of estimating S2 a secondary time base for a processor element 105 for each at least one remote portable electronic camera device in relation to the primary time base comprises the steps of transmitting (S21) at least one request (TR1, TR2, TR3) for time information relating to said at least one remote portable electronic camera device, obtaining (S22) a timing (TTRI, T TR2, T TR3) of the transmission of the request for time information based on the obtained primary time base, obtaining (S23) a response (Rl, R2, R3) for each said at least one remote portable electronic camera device (102) comprising the requested time information in a secondary time base of that remote portable electronic camera device, and determining (S24) the estimate of the secondary time base for the processor element 105 for each at least one remote portable electronic camera device in relation to the primary time base based on the obtained timing of the transmission of the request for time information and the time information comprised in the response for the respective remote portable electronic camera device.

The obtained response (Rl, R2, R3) for each said remote portable electronic camera device may be transmitted to the first portable electronic camera device. The determination S24 of the estimate of the secondary time base for each at least one remote portable electronic camera device is then performed at the first portable electronic camera device. Scheduled timings are then transmitted to the respective remote portable electronic camera device in the secondary time base of that remote portable electronic camera device.

The at least one request (TR1, TR2, TR3) may comprise the obtained timing (TTRI, TTR₂, TTR₃) of the transmission of the request. The determination S24 of the estimate of the secondary time base of the remote portable electronic camera device in relation to the primary time base may then be performed at the each respective remote portable electronic camera device based on the obtained timing (TTRI, TTR₂, T _TR3) of the transmission of the request and the obtained response (Rl, R2, R3). The scheduled timings may then be transmitted to the respective remote portable electronic camera device in the first time base.

The communication between the first portable electronic camera device and at least one remote portable electronic camera device may be performed over a wireless channel with predetermined communication timings, so called connect events. The communication may be performed according to a Bluetooth protocol.

The predetermined communication timings may be unknown. The estimation of a secondary time base for each at least one remote portable electronic camera device may then be performed based on the predetermined communication timings.

However, the predetermined communication timings may be unknown. A plurality of requests (TR1, TR2, TR3) for timing information may then be transmitted S21. The determination S24 of the estimate of the secondary time base for each at least one remote portable electronic camera device may then comprise determining a timing relation between the timing (TTRI, T _TR2, T _TR3) of the transmission of each request and the communication timings based on the information in the respective obtained response. The timing of the transmittal of a next request for timing information may be selected based on the determined timing relation between the timing (TTRI, TTR2, TTR3) of the transmission of the preceding request(s) and the communication timings so as to narrow a time window within which the communication event occurs. It may be that time information relating to directly preceding request(s) are not available. Then, earlier requests may be used in the selection.

The determining S24 of the estimate of the time base may comprise determining a time interval within which the time base lies based on a time window within which it has been determined that the communication event occurs. The requests for timing information may be repeatedly transmitted until the time interval within which the time base lies is within predetermined boundaries.

In fig 7, one example of a scheme for estimating the secondary time base for a remote portable electronic camera device is schematically illustrated. The secondary time base is estimated based on an obtained timing of a transmission of a request for time information from a first portable electronic camera device to the remote portable electronic camera device and the time information comprised in the response from the remote portable electronic camera device.

In the illustrated example a time interval Tl between connect events, i.e. timings when the first portable electronic camera device communicates with the remote portable electronic camera device is known. The example is illustrated in relation to an example wherein the connect time interval Tl=100; this connect time interval is only set for illustrative purposes.

The connect time interval Tl may for example be given in microseconds.

In the illustrated example, the first portable electronic camera device transmits a request for time information at a timing TTRI=50. In the illustrated example, this request for time information is denoted TR1. The request for time information is communicated to the remote portable electronic camera device during a next connect event CE1. The timing TCEI of the next connect event CE1 is not known. However, as the time interval is known, it is known that the next connect event Cl will occur within the connect timing interval Tl, i.e. within

100 microseconds. In response to receiving the request for time information, the remote portable electronic camera device forms a response R1 to the request for time information. The response R1 comprises time information indicating the time of an internal clock of the remote portable electronic camera device. In the illustrated example, the response comprises the time

The time is for example given in microseconds.

Then, a difference between the time of the first portable electronic camera device and the remote portable electronic camera device may be estimated. The estimated time difference may be given as a time interval.

An upper limit for the time difference interval may be determined based on a time difference between the timing T1 of the transmission of the request and the timing information in the response. Thus, in the illustrate example, an upper limit for the time difference interval is A1UL=TRI-TTRI=1200-50=1150 [ps].

Further, as the upper limit has been determined and the connect time interval Tl between connect events in this example is known, this may be used for determined a lower limit for the time difference interval, i.e. the lower time limit is D1i_i_= D1ui_-TI=1150-100=1050 [ps]. Thus, the estimation of the difference between the time of the first portable electronic camera device and the remote portable electronic camera device may be given as a time interval D1 £ [1050, 1150], i.e. D1 = 1100 ± 50 [ps]. However, note that an upper limit can always be estimated, even though the time interval is not known.

The information provided above relating to transmission of the transmission request TR, the formation of the associated response R1 and the time interval Tl may also be used to provide an estimate relating to the timing of the connect events in the time base of the first portable electronic camera device. Thus, the timing of the connect event Cl in the primary time base (i.e. the time base of the first portable electronic camera device) may be estimated as

TcEl_First device =TRI~A1 = 1200— (1100 ± 50) =100 ± 50 [ps].

Accordingly, the next connect event CE2 in the primary time base may be estimated to take place at TcE2_First device =200 ± 50 [ps]. The estimated time difference interval D1 may not be of a satisfactory size. Therefore, the above-described process may be repeated one or more times until the time difference interval is within acceptable boundaries.

Accordingly, in accordance with the illustrated example, the first portable electronic camera device transmits a second request for time information. In the illustrated example, the second request for time information is transmitted at a timing TTR2=180. In the illustrated example, this request for time information is denoted TR2. The time for transmitting the second request for time information may obtained arbitrary or selected. If selected, the time may be selected based on the connect time interval. In the illustrated example, the timing of the transmitting of the second request for time information is selected as an increment larger than the connect time interval Tl. Thus, the second request for time information is selected to occur at a point in time closer to the timing of a following connect event than the first request for time information. It may be that time information relating to directly preceding request(s) are not available, in which case earlier requests may be used in the selection.

The request for time information is communicated to the remote portable electronic camera device during a next connect event CE2.

In response to receipt of the second request for time information, the remote portable electronic camera device forms a response R2 to the second request TR2 for time information. The response R2 comprises as described above time information indicating the time of an internal clock of the remote portable electronic camera device. In the illustrated example, the response comprises the time TR2=1300 [ps].

Then, the estimation of the time difference between the time of the first portable electronic camera device and the remote portable electronic camera device may be updated.

As the time information included in the second response R2 differs with an amount corresponding to the connect time interval Tl between connect events, in this case 100 [ps], it can be concluded that the response was received in a connect event directly following the first connect event. The upper limit for the time difference interval may be updated based on a time difference between the timing T_TR2 of the transmission of the request TR2 and the timing information of the formed response R2.

Thus, in the illustrate example, an upper limit for the time difference is

A2UL=TR2-TTR2=1300-180= 1120 [ps].

At this stage, no information has been obtained for updating the lower time limit.

Thus, the time difference between the time of the first portable electronic camera device and the remote portable electronic camera device has now been updated.

Thus, the estimation of the difference between the time of the first portable electronic camera device and the remote portable electronic camera device has been updated. The time difference may be given as a time difference interval D2 £ [1050, 1120], i.e.

D2 = 1085 ± 35 [ps].

Further, the timing T_CE2 of the connect event CE2 in the primary time base may be estimated as

TcE2_First device ~TR2~A2 = 215 ± 35 [ps].

Accordingly, the next connect event CE3 in the time based of the first portable electronic camera device may be estimated to take place at Tc_E3__{First de ice} =315 ± 35 [ps].

The so determined time difference interval may not be satisfactory small. Therefore, the above-described process may be repeated at least one time to obtain satisfactory accuracy.

Accordingly, in accordance with the illustrated example, the first portable electronic camera device transmits a third request TR3 for time information. In the illustrated example, the third request TR3 for time information is transmitted at a timing TTR3=310. In the illustrated example, the timing T_TR3 of the transmission of the third request TR3 for time information is arbitrary obtained or selected. If selected, the timing T_TR3 of the transmission of the third request TR3 may be an increment in relation to the second request for time information TR2 with a time larger that the connect time interval Tl. Thus, the third request for time information is then selected to occur at a point in time closer to the timing of the connect event than the second request for time information. It may be that time information relating to directly preceding request(s) are not available. Then, earlier requests may be used in the selection.

The request TR3 for time information is communicated to the remote portable electronic camera device during a connect event CE4.

In response to receipt of the third request for time information TR3, the remote portable electronic camera device forms a response to the third request for time information TR3. The response comprises as described above time information indicating the time of an internal clock of the remote portable electronic camera device. In the illustrated example, the response comprises the time TR3=1500 [ps].

As the time information included in the third response differs with an amount corresponding to two connect time intervals Tls between connect events, in this case 200 [ps], it can be concluded that the response was not formed in a connect event CE3 directly following the second connect event but in a thereafter following connect event CE4. This means that the third request TR3 was transmitted at a timing after the third connect event CE3 or at least so close to the timing of the connect event CE3 that the third request TR3 could not be included in the third connect event CE3.

The lower value for the time difference interval may be updated based on a time difference between the timing T3 of the transmission of the request and the timing information of the of received response R3. The lower limit for the time difference may be updated by determining that the request was transmitted after the timing TR3-TTR3=1500 - 310 = 1190 [ps] in the time base of the remote portable electronic camera device and that the lower limit for the time difference then may be updated as the difference between the timing of the third connect event CE in the time base of the remote portable electronic camera device and the timing of the transmission of the third request TR3 in the time base of the first portable electronic camera device.

In practice, the lower limit for the time limit may be calculated as follows. The time difference between the timing T_TR3 of the transmission of the request TR3 and the timing information of the formed response R3 is determined as TR3-TTR3=1500-310=1190. This time difference larger than the previously estimated upper limit, and thus it may be determined that the third request TR3 was transmitted at a timing after the third connect event CE3 or at least so close to the timing of the connect event CE3 that the third request TR3 could not be included in the third connect event CE3

Thus, in the illustrate example, a lower limit for the time difference is D3i_i_=

TR3-T_TR₃-TI=1500-310-100= 1090 [ps].

Thus, the estimation of the difference between the time of the first portable electronic camera device and the remote portable electronic camera device has been updated. The time difference may be given as a time difference interval D3 £ [1090, 1120], i.e.

D3 = 1105 ± 15 [ps].

At this stage, no information has been obtained for updating the upper time limit.

Thus, the time difference between the time of the first portable electronic camera device and the remote portable electronic camera device has now been updated. In this example, the time difference interval has been updated to be D3 £ [1090, 1120] [ps].

Further, the timing T_CE4 of the connect event CE4 in the time base of the first portable electronic camera device may be estimated as

TcE4_First device =395 ± 15 [ps].

Accordingly, a next connect event CE5 in the time base of the first portable electronic camera device may be estimated to take place at Tc_E5__{First de ice} =495 ± 15 [ps].

The so determined time difference interval may not be of a satisfactory size. Therefore, the above-described process may be repeated at least one time using timings of transmissions of the requests TRn in order to further narrow the time interval D.

In fig 8, a modified example of a scheme for estimating the secondary time base for a remote portable electronic camera device is schematically illustrated.

In line with the example of fig 7, the secondary time base is estimated based on an obtained timing TTR of a transmission of a request TR for time information from a first portable electronic camera device to the remote portable electronic camera device and the time information comprised in the response R from the remote portable electronic camera device.

In line with the example of fig 7, a connect time interval Tl between connect events, i.e.

timings when the first portable electronic camera device communicates with the remote portable electronic camera device may be known. The example is illustrated in relation to an example wherein the connect time interval Tl=100; this time connect time interval is only set for illustrative purposes. Tl may for example be given in microseconds.

In accordance with this example, a plurality of transmission requests TR1, TR2, TR3 are transmitted at different, predetermined timings in relation to each connect event. Thereby, the time needed for obtaining a time difference between the first portable electronic camera device and the respective remote portable electronic camera device may be shortened in relation to the example of Figure 7. In the illustrated example, a first transmission request TR1, a second transmission request TR2 and a third transmission request TR3 are transmitted at a first timing TTRI=50 [ps], a second timing TTR2=180 [ps] and a third timing TTR3=310 [ps].

The first and second transmission requests TR1, TR2 for time information are communicated to the remote portable electronic camera device during a next connect event CE1. However, the third transmission request is not communication at that connect event. The third transmission request is awaiting the thereafter following connect event CE2.

In response to receipt of the first and second transmission requests TR1, TR2 for time information, the remote portable electronic camera device forms a response Rl, R2 to the respective first and second requests TR1, TR2 for time information. The responses Rl, R2 to the respective first and second transmission requests TR1, TR2 comprises time information indicating the time of an internal clock of the remote portable electronic camera device. Thus, the response comprises in an example two time indications indicating the same timing. In the illustrated example, the responses comprise the time 1200. The time is for example given in microseconds. The response does not comprise a third time indication as the third

transmission request TR3 has not yet been communicated.

Thus, after the first connect event CE1 of this example, the same information is obtained as after a plurality of connect events in fig 6. Then, a difference between the time of the first portable electronic camera device and the remote portable electronic camera device may be estimated. The estimated time difference may be given as a time interval.

The time difference between the time of the first portable electronic camera device and the remote portable electronic camera device may then be determined to be D £ [1090, 1120] based on the connect time interval information Tl, the timings of the transmission

requests (TTRI=50, TTR2=180, TTR3 =310) and the information that the first and second responses were received at 1200 in the time base of the remote portable electronic camera device in an equivalent manner as described in relation to fig 6.

The example illustrated in relation to figs 7 and 8 are merely examples.

In the herein illustrated examples, some algorithm for selection of timings for transmissions of the transmission requests TR may be used for narrowing the time interval D. The selection may be based on previous responses to transmission requests. It may be that responses relating to directly preceding request(s) are not available. Then, earlier requests may be used in the selection.

Further, in the herein illustrated examples, communication of the request, formation of the response and communication of the response, when applicable take place within the same connect events. However, this is only an example. For example, the communication of the request and the formation of the response may be arranged to take place in one connect event and the communication of the response, when applicable, takes place in a following connect event. In another example, the communication of the request takes place in one connect event and the communication of the response, when applicable, takes place in a following connect event. The teaching as described herein is applicable to all situations, as long as the scheme for communication and formation of responses is known. Should there be occurrences when data falls outside the determined scheme for communication and formation of responses, those data should be ignored.

Further, in the herein illustrated examples, it is assumed that the communication of the transmission request of the first portable electronic camera device, the reception of the transmission request at the remote portable electronic camera device, the processing of the transmission request at the remote portable electronic camera device, the transmission of the response from the remote portable electronic camera device and the receipt of the response at the first portable electronic camera device is performed more or less momentarily. In order to further improve the estimation of the time difference between the first portable electronic camera device and the remote portable electronic camera device, any delays in this scheme may be taken into account when estimating the time difference between the first portable electronic camera device and the remote portable electronic camera device.

Further, the transmission requests may comprise an identity uniquely identifying the request. Transmitted responses then characteristically also comprises the identity uniquely identifying the one or plurality of requests to which the response is associated. Thereby, pairing of the request with its corresponding response is facilitated. When the requests are uniquely identified, this allows for example for discarding retransmissions when estimating the time difference between the first portable electronic camera device and the remote portable electronic camera device. Precision in the estimation may thereby be improved. Further, in practice, the clocks of the first portable electronic camera device and the remote portable electronic camera device will characteristically drift in relation to each other.

Therefore, estimation of the time difference between the primary time base of the first portable electronic camera device and the secondary time base(s) of the remote portable electronic camera device(s) may be performed repeatedly. Thus, the estimation time difference between the first portable electronic camera device and the respective remote portable electronic camera device may take place continuously or at predetermined time intervals.

Claims

1. A computer implemented method (10) for coordinating initiation of a primary event in a first portable electronic camera device (101) having an image sensor (61) and possibly an illumination device (62) configured to emit a flash, and at least one secondary event in at least one remote portable electronic camera device (102b, 102c, 102d) having an image sensor (61) and possibly an illumination device (62) configured to emit a flash, wherein the primary event and/or at least one secondary event is an image capture with the respective image sensor, said method comprising the steps of obtaining (SI) a primary time base for a processor element (105) of the first portable electronic camera device (101), estimating (S2) a respective secondary time base for a processor element (105) of each remote portable electronic camera device (102b, 102c, 102d) in relation to the primary time base, scheduling (S3) a timing for initiation of the at least one secondary event in the primary time base so that coordination of the timing for initiation of the primary event and the timing for initiation of each secondary event is obtained, and obtaining (S4) at the remote portable electronic camera device (102b, 102c, 102d) the respective scheduled timing of initiation of the secondary event in the respective secondary time base of that portable electronic camera device (102b, 102c, 102d).

2. The computer implemented method according to claim 1, said computer implemented method being executed by an app in the first (101) and/or the remote portable electronic camera device (102b, 102c, 102d).

3. The computer implemented method according to any of the preceding claims, wherein the step of estimating (S2) a respective secondary time base for a processor element (105) of each remote portable electronic camera device (102b, 102c, 102d) in relation to the primary time base comprises the steps of transmitting (S21) at least one request (TR1, TR2, TR3) for time information relating to the remote portable electronic camera device (102b, 102c, 102d), obtaining (S22) a timing (TTRI, T TR2, T TR3) of the transmission of the request for time information based on the obtained time reference of the first portable electronic camera device (101), obtaining (S23) a response (Rl, R2, R3) for each remote portable electronic camera device (102b, 102c, 102d) comprising the requested time information in a time base of that remote portable electronic camera device (102b, 102c, 102d), and determining (S24) the estimate of the respective secondary time base for the processor element (105) of each at least one remote portable electronic camera device (102b, 102c, 102d) in relation to the primary time base based on the obtained timing of the transmission of the request for time information and the time information comprised in the response for the respective remote portable electronic camera device (102b, 102c, 102d).

4. The computer implemented method according to claim 3, wherein the obtained response (Rl, R2, R3) for each said remote portable electronic camera device (102b, 102c, 102d) is transmitted to the first portable electronic camera device (101) and the determination (S35) of the estimate of the time base for each at least one remote portable electronic camera device (102b, 102c, 102d) is performed at the first portable electronic camera device (101), and wherein the scheduled (S4) timing is transmitted to the respective remote portable electronic camera device (102b, 102c, 102d) in the time base of that remote portable electronic camera device (102b, 102c, 102d).

5. The computer implemented method according to claim 3, wherein the at least one request (TR1, TR2, TR3) comprises the obtained

timing (TTRI, TTR2, TTR3) of the transmission of the request and the determination (S35) of the estimate of the time base for the remote portable electronic camera device (102b, 102c, 102d) in relation to the time base of the first portable electronic camera device (101) is performed at the remote portable electronic camera device (102b, 102c, 102d) based on the obtained timing (TTRI, TTR₂, TTR₃) of the transmission of the request and the obtained response (Rl, R2, R3), and wherein the scheduled (S4) timing is transmitted to the respective remote portable electronic camera device (102b, 102c, 102d) in the time base of the first portable electronic camera device (101).

6. Method according to any of the preceding claims, wherein the scheduling of a timing is performed at least in part in the first portable electronic camera device (101).

7. The method according to any of the preceding claims, wherein the communication

between the first portable electronic camera device (101) and at least one remote portable electronic camera device (102b, 102c, 102d) is performed over a wireless channel with predetermined communication timings, so called connect events, and wherein the estimation of a time base for each at least one remote portable electronic camera device (102b, 102c, 102d) is performed based on the predetermined

communication timings.

8. The method according to claim 7, wherein the predetermined communication timings are unknown, wherein a plurality of requests (TR1, TR2, TR3) for timing information are transmitted and wherein the determination of the estimate of the time base for each at least one remote portable electronic camera device (102b, 102c, 102d) comprises determining a timing relation between the timing (TTRI, TTR₂, TTR₃) of the transmission of each request and the communication timings based on the information in the respective obtained response.

9. The method according to claim 8, wherein the timing of the transmittal of a next request for timing information is selected based on the determined timing relation between the timing (TTRI, TTR₂, TTR₃) of the transmission of preceding request(s) and the

communication timings so as to narrow a time window within which the communication event occurs.

10. The method according to claim 8 or 9, wherein the determining of the estimate of the time base comprises determining a time interval within which the time base is based on a time window within which it has been determined that the communication event occurs.

11. The method according to claim 10, wherein requests for timing information are

repeatedly transmitted until the time interval within which the time base is within predetermined boundaries.

12. The method according to any of the claims 7 - 11, wherein communication is performed according to a Bluetooth protocol.

13. The method according to any of the preceding claims, wherein the primary event is an image capture with the image sensor of the first portable electronic camera device

(101).

14. The method according to any of claims 1-12, wherein the primary event is an emission of a flash with the illumination device of the first portable electronic camera device.

15. The method according to any of claims 1-13, wherein at least one secondary event is an emission of a flash with an illumination device of the respective remote portable electronic camera device (102b, 102c, 102d).

16. The method according to any of claims 1-14, wherein at least one secondary event is an image capture with the image sensor (61) of the respective remote portable electronic camera device (102).

17. A control system (200) for coordinating initiation of at least a primary event and at least one secondary event in a plurality of portable electronic camera devices (101, 102b,

102c, 102d), each having an image sensor (61) to capture an image and possibly an illumination device (62) configured to emit a flash, said control system (200) being arranged to control the initiation of the primary event in a first portable electronic camera device (101) among the plurality of portable electronic camera devices (101, 102b, 102c, 102d), said first portable electronic camera device (101) having a processor element (105) operating in a primary time base, and the initiation of the at least one secondary event in at least one remote portable electronic camera device (102b, 102c, 102d) among the plurality of portable electronic camera devices (101, 102b, 102c, 102d), each remote portable electronic camera device (102b, 102c, 102d) having a processor element (105) operating in a respective secondary time base, wherein the primary event and/or at least one secondary event is an image capture with the respective image sensor (61), said control system comprising, a time base estimating element (211) arranged to estimate a relation between the primary and the respective secondary time bases, a scheduler element (210), arranged in one of the portable electronic camera devices, and arranged to schedule in the primary time base a timing for initiation of said at least one secondary event so that coordination of the timing for initiation of the primary event and timing for initiation of said at least one secondary event is obtained, and a communication interface (212) arranged to transmit to the respective remote portable electronic camera device (102b, 102c, 102d) the scheduled timing for initiation of a flash pulse and/or for initiation of image capture of that remote portable electronic camera device (102b, 102c, 102d).

18. The system according to claims 17, wherein the time base estimating element (211) is arranged to request transmission of at least one request (TR1, TR2, TR3) over said communication interface (212) time information relating to said at least one remote portable electronic camera device (102b, 102c, 102d), obtain a timing (TTRI, T TR2, T TR3) of the transmission of the request for time information based on the obtained primary time base of the first portable electronic camera device (101), obtain a response (Rl, R2, R3) for each said at least one remote portable electronic camera device (102b, 102c, 102d) comprising the requested time information in a secondary time base of that remote portable electronic camera device (102b, 102c, 102d), and determine the estimate of the secondary time base for the processor element (105) of each at least one remote portable electronic camera device in relation to the time base of the processor element (105) of the first portable electronic camera device (101) based on the obtained timing of the transmission of the request for time information and the time information comprised in the response for the respective remote portable electronic camera device (102b, 102c, 102d).

19. The control system according to claims 18, wherein the obtained response (Rl, R2, R3) for each said remote portable electronic camera device (102b, 102c, 102d) is transmitted to the first portable electronic camera device (101) over the communication interface (212) and wherein the time base estimating element (211) is arranged to determine the estimate of the time base for each at least one remote portable electronic camera device (102b, 102c, 102d) time base at the first portable electronic camera device (101), and wherein the scheduler element (210) is arranged to feed to the communication interface (212) the scheduled timing for initiation of a flash and/or for initiation of image capture for the respective remote portable electronic camera device (102b, 102c, 102d) in the secondary time base.

20. The control system according to claims 18, wherein the at least one request (TR1, TR2, TR3) comprises the obtained

timing (TTRI, TTR2, TTR3) of the transmission of the request and wherein the time base estimating element (211) is arranged to determine the estimate of the secondary time base for each at least one remote portable electronic camera (102b, 102c, 102d) device at the respective remote portable electronic camera device (102b, 102c, 102d) and wherein the scheduler element (210) is arranged to feed to the communication interface (212) the scheduled timing for initiation of a flash pulse and/or for initiation of image capture for the respective remote portable electronic camera device (102b, 102c, 102d) in the primary time base.

21. A portable electronic camera device (101) arranged to coordinate initiation of a primary event in said portable electronic camera device and initiation of at least one secondary event in at least one remote portable electronic camera device (102b, 102c, 102d), said portable electronic camera device (101), comprising an image sensor (61) and possibly an illumination device (62), and a processor element (105) operating in a primary time base, wherein the at least one remote portable electronic camera device (102b, 102c, 102d) comprises an image sensor (61) and possibly an illumination device (62), and a processor element (105) operating in a respective secondary time base, wherein the primary event and/or at least one secondary event is an image capture with the respective image sensor (61), said portable electronic camera device (101) comprising at least a part of a time base estimating element (211) arranged to estimate a relation between the primary and the respective secondary time bases, a scheduler element (210) arranged to schedule in the primary time base a timing for initiation of said at least one secondary event in the respective remote portable electronic camera device so that coordination of the timing for initiation of the primary event and the timing for initiation of said at least one secondary event is obtained, and a communication interface (212) arranged to transmit to the respective remote portable electronic camera device (102b, 102c, 102d) the scheduled timing of said remote portable electronic camera device (102b, 102c, 102d).

22. The portable electronic camera device (101) according to claim 21, wherein the portable electronic camera device (101) is arranged to communicate with the at least one remote portable electronic camera device via a Bluetooth interface.

23. The portable electronic camera device (101) according to claim 21 or 22, wherein the primary event is an image capture with the image sensor (61) of the portable electronic camera device (101).

24. The portable electronic camera device (101) according to any of claims 21 or 22, wherein the primary event is an emission of a flash with the illumination device (62) of the portable electronic camera device (101).

25. The portable electronic camera device according to any of claims 21-23, wherein at least one secondary event is an emission of a flash with an illumination device (62, 62b, 62c) of the respective remote portable electronic camera device.

26. The portable electronic camera device according to any of claims 21-24, wherein at least one secondary event is an image capture with the image sensor (61, 61b, 61c, 61d) of the respective remote portable electronic camera device (102b, 102c, 102d).

27. A computer program product for performing the method for coordinating initiation of a flash from at least one portable electronic camera device (101, 102b, 102c, 102d )and image capture using an image sensor (61, 61b, 61c), according to any of the claims 1-16.