Hardware for camera array trigger

30_08 wrote:

Hello!

I read thread about "bullet-time effect" (https://www.dpreview.com/forums/thread/4031596) and i had a question about this. Which hardware should be use for remote camera array in time? Simple USB cables bad because it can delay cameras about 1/10sec. BreezeSys advice to use TriggerBox by Esper for avoid delay between cameras. It's good, but maybe there are others solutions for this?

General question - what are the hardware solutions for remote cameras array?

There is no general answer. It depends on the cameras used.

Canon PowerShot cameras that are supported by CHDK can sync very precisely (to about 1/1000s, sometimes better) by triggering when they see 5V applied to their USB.

Lots of older cameras have a three-conductor wired remote that works as a ground and half-press and full-press; you connect ground to half-press, wait a bit, then also connect full-press to ground to fire the shutter. That's what BreezeSys is talking about here .

Basically, the issue is that most cameras have a little lag as they do the half-press (focus and set exposure), and normal tethered-USB operation asking for the shutter to be pressed can suffer that delay. The actual USB delay can be pretty small, and for USB2 the communication protocol delay is less than 120us (i.e., 0.00012s), so it really just depends on how the camera handles the shoot request. With Canon PowerShots under CHDK, you can actually control things well enough that you can trigger quite precisely using an actual USB message (rather than just detection of 5V), but then there's the scaling problem that USB commands to multiple cameras sharing the same USB connection will get serialized, adding a little delay... whereas any number of cameras can detect the 5V simultaneously without any scaling issue.

The other option is to do sloppy sync, but flash the light -- dark room, long exposure, fire a strobe to capture from all cameras at the same moment (usually about 1/1000s duration for a strobe).