Sync multiple cameras too single flash - a delay circuit?

[Michael Durham]

Sadly, my ability to understand and absorb basic electronics is rather limited - But let me describe what I am trying to do, and how most of the problems have been solved. Ideas on how to proceed are welcome. I apologize in advance for the long post.

I have made my living as a nature photographer for many years, and much of my work has been built around using a camera to photograph subjects or events that are typically hidden from human eyes. You can see a few samples here: **broken link removed**

My current issued involves using multiple cameras for a custom trail camera set. With this system, I use three cameras to photograph a trigger event. Each camera will record a different view of the same moment. Most events happen at night, so electronic flash is used to creatively light the scene. With multiple cameras, there is a 'master' camera that triggers the flash units. The other cameras are 'slaved' to the master.

In other words, all of the cameras will use the same flash units for the photograph. With my old film camera set, I could easily time the cameras and determine which was slowest to open its shutter, and once determined, this remained consistent. The slowest camera becomes the master because, when everything works correctly, the other cameras will have already opened their shutters when the flash units are triggered by the master.

Now however, I am using Canon 20d digital bodies for this work. Digital, as you might imagine, provides far superior results and allows me to see if I have been successful instantly. This saves time and money.

The problem with the Canon 20d is that the timing of the cameras is not consistent. It has taken a while for me to figure this out, but the response time of each camera can vary by microseconds over time which makes it impossible to determine a 'master' camera.

Setting the flash sync to 'rear curtain' on the master camera would solve this problem, however Canon does not provide this setting for "non-canon" flash units (which I must use).

My thought is that if I could just slightly delay (by a few microseconds) the flash sync signal consistently, that this would allow me to solve this problem.

I ordered a simple delay circuit kit (http://hiviz.com/kits/du.htm), that uses a 555 timer, however my attempts to build it have met with failure. I have replaced components, triple checked my wiring – but it just does not work. I have no doubt that this is an error on my part. I have spent many hours over several days trying to build and trouble shoot the circuit and I am not even sure that it would suit my needs.

The cameras will need to be active and ready to trigger, at a moments notice, over several weeks. I'm not sure that the 9 volt battery for this delay circuit, and the power requirements would allow it to function over that length of time.

I am looking for an elegant and simple solution for delaying, by microseconds, the flash output sync signal. Preferably one that does not require much power. It would also be handy if I could purchase this ready made or hire someone to make it for me.

A few important details. Some of my flash units have very high sync voltages (on the order of 240 volts). These flash units were custom built to stay powered up, and ready to flash, for weeks on end.

The entire system can currently fit in one large backpack, and I am trying to keep things as light and portable as possible.

I'm not sure if there are details that I missed.

Any advice would be appreciated.

Thanks

MD

 

[Mikebits]

The 555 timer would be a bad choice for microsec accuracy as they tend to have a lot of drift.
One question I have is how are the camera flashes triggered? Is it a switch closure, a voltage, if the latter, what voltage?

 

[Michael Durham]

Good question. On the camera terminal I measure .5 volts when triggered, otherwise there is nothing.

coming from the flash, however, there can be significant voltage. One of my flash units measures 180 volts. Once triggered the voltage drops significantly, and slowly builds up as the cap is recharged.

Another flash has a consistent 8 volts on the sync cord.

The camera sync terminal is rated for up to 250 volts.

MD

 

[Mikebits]

I am not familiar with how this works. So I imagine a master camera which provides flash control to slave cams. Something like attached image. Is this thinking wrong?

 

[Mikebits]

Or is it more like this. We need to understand the interface, this is why I ask.

 

[Michael Durham]

I really appreciate your thoughts on this.

I have included a diagram to show the relationship between the cameras, sensor and flash.

The master camera is the slowest to open the shutter. The shutter trips the flash, and the other two cameras will have their shutters already open.

The sensor trips all three cameras, but only the master camera triggers the flash discharge.

Thanks

MD
**broken link removed**

 

[Michael Durham]

If I can delay the flash discharge by a few microseconds, then I should be able to get all of the cameras to see the light consistently.

 

[Mikebits]

I think I found the interface info for your camera remote. I hope anyways Take a look at this link and tell me if this sounds about right.
https://www.diff.net/peter/photography/canon_n3_connector_info.shtml

If this is your control input then that would explain why your timer circuit did not work as you need to emulate a switch closure. Maybe the input is an active low, meaning the line needs to be pulled low.

 

[Michael Durham]

I think I found the interface info for your camera remote. I hope anyways Take a look at this link and tell me if this sounds about right.
https://www.diff.net/peter/photography/canon_n3_connector_info.shtml

If this is your control input then that would explain why your timer circuit did not work as you need to emulate a switch closure. Maybe the input is an active low, meaning the line needs to be pulled low.

That looks correct. However the camera terminals are not really part of the problem.

What I am hoping to do is delay the flash output from the master camera. I want all three cameras to be triggered at the same moment, but I want the flash output slightly delayed.

It would be great if I could plug in a small device between the camera and flash, that would allow an adjustable delay.

I'm not sure this is even possible.

MD

 

[jpanhalt]

I do not understand why you need the delay to be a few microseconds. Sure, that is doable, but it is dark. A millisecond delay delay would be easy to get with a one-shot based on a 555, for example. What would be the problem with having the shutters open before the flash for a longer period, such as 1 to 5 milliseconds? Isn't it the flash, not the shutter time that controls the exposure when it is dark? I apologize for my ignorance of photography, if the answer is obvious.

John

 

[Mikebits]

That looks correct. However the camera terminals are not really part of the problem.

I realize we are not worried about the terminals, but we need to understand the mechanism which triggers the camera. From the web link I provided, it looks like the shutter is triggered by applying a common terminal to the shutter pin in other words a simple contact closure, or maybe just pulling the shutter pin low.

What I am hoping to do is delay the flash output from the master camera. I want all three cameras to be triggered at the same moment, but I want the flash output slightly delayed.

It would be great if I could plug in a small device between the camera and flash, that would allow an adjustable delay.

I'm not sure this is even possible.

It is possible once we understand the interface. I am leary to just say try this or that since we are dealing with expensive gear. I have no experience with cameras so I am leaning on the side of caution. I would hate to hear you say "Thanks for the advice, now my camera is blown up"

MD

Well I hope that makes sense.
What would be ideal is an actual interface spec for the shutter pin. I looked on the cannon web site but did not find one. Maybe it is in your camera manual.

 

[Michael Durham]

I do not understand why you need the delay to be a few microseconds. Sure, that is doable, but it is dark. A millisecond delay delay would be easy to get with a one-shot based on a 555, for example. What would be the problem with having the shutters open before the flash for a longer period, such as 1 to 5 milliseconds? Isn't it the flash, not the shutter time that controls the exposure when it is dark? I apologize for my ignorance of photography, if the answer is obvious.

John

John - thanks for your question.

Three cameras are being used to record the scene from one flash unit. To allow this, all the cameras must be synced and timed. The slowest camera, will drive the flash by virtue of the fact that the other two cameras will already have their shutters open. Therefore all cameras will record the same moment from different angles using the same illumination.

Ideally, this occurs in the dark. You are correct that the flash output controls the exposure (and freezes action).

Here are a couple of real world examples.

Kangaroo Rat: Camera A

**broken link removed**

Kangaroo Rat: Camera B

**broken link removed**

These are the exact same moment, captured by two different cameras. I think Camera B got the best image.

Again. Mountain Lion: Camera A

**broken link removed**

Mountain Lion: Camera B

**broken link removed**

The same flash units light the scene at the exact same moment. The trick is getting multiple cameras timed correctly to capture the flash. By the way, the cameras were in place for five weeks before getting these cougar images.

The Canon 20d is ideally suited for digital remote photography for a variety of great reasons. However they suffer from inconsistent timing which makes it very challenging to get all the shutters open before the flash is discharged.

If I could delay the flash slightly and controllably, then I could be sure that all the cameras were capturing the image.

 

[Michael Durham]

Originally Posted by Michael Durham
That looks correct. However the camera terminals are not really part of the problem.

I realize we are not worried about the terminals, but we need to understand the mechanism which triggers the camera. From the web link I provided, it looks like the shutter is triggered by applying a common terminal to the shutter pin in other words a simple contact closure, or maybe just pulling the shutter pin low.

What I am hoping to do is delay the flash output from the master camera. I want all three cameras to be triggered at the same moment, but I want the flash output slightly delayed.

It would be great if I could plug in a small device between the camera and flash, that would allow an adjustable delay.

I'm not sure this is even possible.

It is possible once we understand the interface. I am leary to just say try this or that since we are dealing with expensive gear. I have no experience with cameras so I am leaning on the side of caution. I would hate to hear you say "Thanks for the advice, now my camera is blown up" Well I hope that makes sense.

What would be ideal is an actual interface spec for the shutter pin. I looked on the cannon web site but did not find one. Maybe it is in your camera manual.

OK

A simple circuit closure will trip the camera, however it has to be awake. The cameras are usually asleep, so there is a pulse to wake them up and then a pulse to trigger them. This really saves on battery power, and allows the cameras to last for four weeks or more in the field.

I made the cord that goes from the sensor to the camera myself. I used a cheap knock-off (chinese) Canon remote cord and stripped it down to the wire. I experimented with shorting the three wires in various combinations until I was able to get the sensor to properly wake-up and trigger the camera.

Here is a pin out description of the camera port: https://www.camerahacker.com/Canon/Canon N3 Connector Pin-Out.php

Thanks!

MD

 

[Mikebits]

Those photo's are great and fascinating. How do you get those shots without spooking the animals? Do you have the cams just sit in one place and have some sort of motion sensor that triggers when an animal walks by? Maybe these are trade secrets so I won't push for an answer
Damn nice pics though... Wow is what comes to mind, very cool.

 

[Michael Durham]

Those photo's are great and fascinating. How do you get those shots without spooking the animals? Do you have the cams just sit in one place and have some sort of motion sensor that triggers when an animal walks by? Maybe these are trade secrets so I won't push for an answer
Damn nice pics though... Wow is what comes to mind, very cool.

Thanks Mike

There aren't really any trade secrets. It takes persistence and knowledge of your subject. Time is the principal element. Some of these shots can two months to get.

MD

Did the pin-out url help?

 

[Mikebits]

Did the pin-out url help?

Yes it confirms a few things. I think we can proceed. I have an idea that should work but need to put into a drawing for ya.

 

[mneary]

1) You could take the flash trigger from all three cameras and apply them to an AND gate (don't need to use a "real" gate). If I have time to draw this later, I will, unless somebody beats me to it.
2) You can get a fairly consistent (short) delay with a reed relay. No circuitry required.

 

[Michael Durham]

1) You could take the flash trigger from all three cameras and apply them to an AND gate (don't need to use a "real" gate). If I have time to draw this later, I will, unless somebody beats me to it.
2) You can get a fairly consistent (short) delay with a reed relay. No circuitry required.

A reed relay sounds simple and easy. I would have no idea how to impliment, and also i wonder about the the sync voltage of the flash. One flash has a sync voltage of 180 volts, the other 8 volts.

Thanks!

MD

 

[Mikebits]

A reed relay sounds simple and easy. I would have no idea how to impliment, and also i wonder about the the sync voltage of the flash. One flash has a sync voltage of 180 volts, the other 8 volts.

Thanks!

MD

Doesn't the camera control the flash? Are we not just boinking the shutter pin? I'm confused...

 

[mneary]

A reed relay would require experimentation to get the timing right, but here's what I would do:

Take the flash sync from one of the cameras, wire it with 3V worth of AA's in series with a reed relay such as this one from All. If it's too slow, use a higher battery voltage - the relays won't care, if the pulses are short enough to keep the power reasonable.

Use the multiple contacts to trigger different flash units without interference.