Sync multiple cameras too single flash - a delay circuit?

[Michael Durham]

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

I'm probably not explaining this well. I don't want to delay the camera reaction to the sensor. I want to delay the flash response to the shutter.

I don't want to slow down the camera, just the flash reaction. It would be simple if Canon allowed "rear curtain sync" on non-canon flash, because then I could just make the flash trigger upon shutter closing instead of shutter opening.


HOWEVER, In principal - slowing the reaction of one camera's response to the sensor (ever so slightly) would also do the same thing. (Which isn't a bad idea at all)

Now I understand why you wanted the pin-out on the camera remote port!

MD

 

[Mikebits]

Posted is an image of what my approach to your timing dilemma would have been. Let me know if this is off base. If it sounds feasable to you, I will post my circuit for implementing this.

P.S. I start school on Monday, so after that, my free time will be limited

 

[AllVol]

I'm probably not explaining this well. I don't want to delay the camera reaction to the sensor. I want to delay the flash response to the shutter.

I don't want to slow down the camera, just the flash reaction.

I might be way off base here, but isn't the problem one of semantics? Aren't you really saying you want the flash duration extended so all cameras can capture the moment?

When you say flash delay, I think in terms of withholding the flash until all cameras are operative. I remember when electronic flash first became widely available for photography. We used the speed of the flash unit to stop drops of water falling and such, as opposed to the slower flash-bulbs, which generated a longer-lasting light.

Just a thought.

 

[sergesret]

Just stumbled on this thread. I'm working a similar problem to this one, namely synchronizing two cameras to get stereo photos. A flash may or may not be involved in making the photo. I ran across a commercialized product called the SLR Shepherd that implements this function: http://www.ledametrix.com/slrshep/index.html . The key idea of this system is that the flash sync from a camera gives a reliable signal of the instant shutter is actually openned. Therefore, you can obtain the shutter lag from measuring the time difference between closing the shutter button to receiving the flash sync trigger from the camera. If you measure the shutter lag for each camera, you can stagger the shutter triggers for each camera such that the flash sync from each camera arrives simultaneously. This process can be expanded to any number of cameras. By definition this synchronizes the flash between all of the cameras.

I'm in the process of building my own version of this synchronization process using an AVR microcontroller. This is my first AVR project so it's taking me a bit of time to ramp up. For the first phase I'm most of the way through implementing a single camera intervalometer. Once I get this working I'm going to go the rest of the way and start measuring the shutter lag to build out the multi camera part of the project.

What I can looking for here was some hints on how to get the flash sync signal out of the camera. The shutter close is very simple. You just short out the appropriate terminals on the remote release. Simple enough to do with something like an opto coupler or some transistors. But the flash sync seems to be a weird beast. I was hoping that it was a simple relay in the camera closing to complete an external circuit. But hooking up my multimeter to the X sync terminal I not only got some odd voltage readings but the camera didn't function correctly with the meter attached. I found that anything less than a 10K resistor across the X terminal would cause the camera to not work. This is a Canon camera, by the way, if that matters. From what I've gleaned so far, there is something more than a simple relay in the camera, but exactly how to convert what the X sync gives you into a bit on a microcontroller input port I'm not sure.

So, if anyone has any helpful details on how the flash sync is implemented on the camera side of a Canon camera that would be helpful. I'm also interested in trading notes with anyone interested in camera synchronization in general.

 

[jmb4370]

Pocket Wizard is a line of radio controllers for firing remote cameras and flash units, and is the gold standard in pro photography. The MultiMax version has this ability to both time and analyze the shutter lag of a given camera, so that multiple cameras can be synced to a single flash unit. The idea is to find the camera with the slowest time, and this becomes the zero point for when the flash is fired. The faster acting cameras are then delayed by the number of microseconds they are faster than the slowest camera.

This is how it is done in arenas and other places where multiple cameras are sharing the same strobes.

Michael

 

[Rolf]

{snip}

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

I have a little experience with optical slave triggers, see; Slave Flash Trigger Kit, Optical with PIC Controller, Ver.III Photo Gallery by Rolf at pbase.com

As I see it the simplest way to do it is to use one camera to trigger an external flash optically, block of any of the light that could fall on the subject use it only to trigger the remote slave trigger and it's flash. You would probably need to play with the shutter speed on the two other cameras in order for them to be open when the flash triggers. You might also have to play with the set up in order to get the slowest triggering camera to do the flash triggering. And you might have to set the two fastest cameras shutter speed fairly slow like a 1/25 sec. but this will be no problem in the dark.

Rolf

P.S. If you would like to talk about this, you can find me on Skype as "sinoline"

 

[mtrxmek]

Could you please post your modification of your camera sync cable. I am interested in syncing the shutter release on three 20d's

 

[pixnum]

Try to use two silver reflectors with a powerful flash unit. Place your camera angle in such a way that after flashing from main flash unit then the light will travel from first reflector to second reflector to then camera lens. In this way process will be completed. It will cut your money and tension. If your picture still need some manipulation,then photoshop will do rest !

 

[rolland_elliott]

follow up

I'm just curious if you ever found a solution. I am looking to the do the same thing but with around 9 cameras to make 3d lenticular prints or do Matrix type "bullet time special effects" . Any guidance would be appreciated.

Thanks, Rolland

 

[Big Lemon]

Try locating a Remote flash such as the ones they use on RED LIGHT CAMERAs. I used to install these Robo-Cops and the Flash was on a Delayed Trigger board. Frame Grabber events where designed into the operation of the unit. But there was a Flash unit that sits at the corner to capture the 2nd shot of the car in the intersection based on the cars Speed or Trigger if you will. The Flash units had an adjustable Pot on the rear from 0 to 1.5 seconds. I forgot the name of the unit but I think it would do what you want. What is your Triggering system? Motion? or infrared heat? Oh yeah the Flash Bulb was HUGE on this thing about 1/2 inch thick circular bulb, about 8 inches in diameter.

 

[adamey]

Maybe I'm missing the obvious here, but why do you need to have the camera itself trigger the flash? Why not have a circuit that triggers all 3 cameras and then triggers the flash?

What sort of shutter speeds are we talking about? Are they long exposures? If they're short exposures (like 1/60 sec) then how could you even begin to guarantee that 3 cameras would still have their shutters open at the same time to be able to allow the flash to provide consistent illumination?

I can think of a really simple circuit that would give the camera the "wake-up" pulse, the shutter release pulse and then the flash trigger, but it would really only work well with longer exposures.