sync 550d and USB connection problem

[Dannykwon]

Please some one help...

1.

I have a very big difficulty to synchronizing 12 canon 550D..

Do I have to upgrade ? as 600D? , some one says.. it is better .

If I want to sync 12 cameras with 2 light stobe ?

I would like to use 1/200 Speed 16F iso 100.

I am sick of tired seeing black picture...

2.

I am using apple OSX.
when I try to connect 12 cameras with 2 hubs which have their own power, 7ports each of them.
they are very unstable ..
I am Using Mac which has 2 USB ports.
any one help?
they are disconnected time to time.

Please help

[Magnus]

Hello!

1. Unless your surroundings are very bright you should not need such a high shutter speed (and it probably wont work anyway).
What most do with multicamera setups is having longer shutterspeeds (I've used 1/5th or 1/8th or so when mixing different models and brands of cameras) and freezing the subjects with the flash strobes.
By having longer shutterspeeds you can make it so that the flash occurs during the shutter being open, even with different cameralags.
What brand of flash strobes do you have?
Something that might be needed is to have a delay on the firing of the strobes, this can be done with triggers like some models of PocketWizards for example.
Or you could trigger the strobes with a Speedlite if you have one, I can describe more about that if you need.

2. I used a Macbook Air with OSX and had lots of problems with the USB connection but when I installed Windows 7 thru Bootcamp on that same computer it worked fine with multiple cameras. That's my limited experience of that.

Hope this helps a bit.

Best, Magnus.

[Lambo]

Yes as Magnus described, you don't need speeds that fast on the shutter for that since the Flash is the one that dictates the speed.
Another trick you can use is what I am using, that is to have a transmitter on 1 of the cameras (connected to the horseshoe) that sends the flash signal and put that camera to shoot a flash WITH THE SECOND CURTAIN. That will make it shoot the flash (or send the signal for it to the external flash) closer to the end of the shutter time you have set on your cameras. That way you make sure all the cameras have their shutters open by then.
Basically I have all cameras of the same exact model (that helps with synchronization) and I can set them as fast as 1/20 maximum before they start showing black lines.
But using 1/10 I get consistent good results.

Leo

[Lambo]

Another thing, if you are shooting static subjects, then the main light before the flash doesn't matter too much, but if you are gonna shoot anyone moving, you want the main light to be as dim as you can since you will get a ghosting effect specially behind hair that is moving.
Leo

[Dannykwon]

Thank you for your help Leo,
first of all,
I solved Usb Problem. Thank you 360.
But the shatter speed..
I have stil have difficulty to sync.
although I use 1/10 speed , Iso 100, F16.
there are still many black images...

My camera all connected by wire... as long as strobe too, not wireless to have perfect sync.
I am using mirror up setting too.

DO I HAVE TO USE Consistent LIGHT? USING ISO 400 ?

[Magnus]

Hello Danny!

It sounds like you will need to find a way to delay the triggering of the strobes. The cameras usually have a delay of some 10s of ms after the trigger is pushed.

One thing you can try is to half-press the trigger you use for the cameras (which is usually used for focusing), they should be beeping now and then press down fully to trigger the cameras and see if that atleast helps. Or does the strobes go off with half-press?

Btw, you have the cameras set to manual focus?

Best, Magnus.

[Lambo]

Yes, Magnus is right, I forgot to tell you that the autofocus delays the cameras a little bit, enough to make those black images.
But the man problem is that you are triggering the strobe at the same time as the cameras and that will not work without some kind of delay.
Somehow you have to connect your flash with the camera signal and put the camera to flash on the second curtain to add that small delay you need.
Leo

[Dannykwon]

Thank you for your help.
I really appreciate it.
My strobe is this
http://m.ebay.com/itm/Fomex-E400-Studio-400W-Digital-Flash-Strobe-Light-Head-w-Reflector-for-PHOTO-NEW-/251337420308

I have 12 550d and these 2 strobes.
I think my strobe doesn't support second curtain.
Having some delay.. Do i have to buy
Camera axe?

[Lambo]

The strobes don't have to support second curtain, that is a feature of the camera as to when it fires the flashes.
What you have to do is to set 1 of the cameras to fire flash on the second curtain ( I dont know how to do it on Canons since I am using Nikons but it is easy to find on the net )
Then you connect this to the hot shoe of that camera for example:   http://www.paulcbuff.com/cst.php
Then you connect this to your strobe:  http://www.paulcbuff.com/csr.php  (it is recommended to use the AC version since it plugs to the wall and has a wire that keeps going to your strobe )
You should need to connect only one to 1 strobe since most strobes can sync to the other strobe automatically as Master and Slave.
Also I see that at the bottom of the link you sent for your strobe, it shows the adapter to connect the strobe to the hot shoe of your camera with a cable, if that is what you are using, then you don't need the wireless ones I described above.
All you need to do is to set the camera that has that adapter to fire the flash on the second curtain.
Leo

[tommyboy]

Canons in particular have a high level of variability in shutter lag, so even firing on the second curtain, you are probably going to get some black frames. It is definitely important to prefocus cameras before firing as this greatly reduces the variability in shutter lag, but it still happens. Most reliable is to introduce the delay as suggested, for which the formula is:

1) Set shutter speed to be somewhat long (1/10 generally as mentioned by many)
2) Introduce a delay for the strobe firing that is 1/2 of the shutter speed, for best chance of all shutters being open when the strobes fire.

This is the approach that I have used to great success, you can get the shutter speed lower still even, but why bother when this works 100%.

In our case we use a PocketWizard Plus X (cheapst model) to transmit the signal, and MultiMax to receive the signal and introduce the 1/20 second delay before passing the signal on to the strobe. I believe a Camera Axe will allow you to do the same thing for cheaper, but requires a bit more work to set up.