High-speed video with timelapse

[scrax]

That's a feat that I'm thinking about for some time now, but don't know if could work.

The idea is to shoot a constant repetitive fast event like an industrial machine doing his job quickly with a camera triggered by the machine movement at a constant time. After each pic camera will add a 1/n of delay before tacking a pic and wait for another trigger. That way we will have in the end a sequence of the machine states with n being our fps

To trigger camera I think I can make a simple mechanical switch that go in to cable release port.
PicoC will be good I think to implement the delay but is the camera precise enough?
Also was thinking about using audio trigger but don't know a lot on how it could be best way to do it.
We can't go faster than 1/4000 on 600D but i thing that 1/500 will be already interesting.

[eduperez]

Or you could use a plain intervalometer, configured with an interval just slightly larger than the machine's cycle; main problems is that your machine needs a stable speed, and you must precisely measure the cycle.

[wolf]

In my experience picoc isn't precise enough. I would trigger a laptop or a microcontroller that triggers the camera with increasing delay.
Looks like an interesting projekt.

[a1ex]

So, in order to get a 25p video of 1 machine cycle, you will record 25 timelapses, each at 1 image/second, and then assemble them in a movie?

Let's say a machine cycle takes 3 seconds and it's repeated after 10 seconds (so a cycle is 10 seconds).

Then you would take:
timelapse 1: pictures at 0, 1, 2, 3 seconds
timelapse 2: pictures at 10.04, 11.04, 12.04, 13.04 seconds
timelapse 3: pictures at 20.08, 21.08, 22.08, 23.08 seconds
timelapse 25: pictures at 240.96, 241.96, 242.96 and 243.96 seconds

and then you play back the frames at 0, 10.04, 20.08, ... 240.96, 1, 11.04 and so on.

Is this correct?

If so, I suggest using the DIGIC timer at 0xC0242014. It wraps after 1048576 ticks, which correspond to 1 second. Take a look at seconds_clock_task.

Triggering a frame can be done with +/- 10ms timing accuracy afaik (from my bulb tests). Try in audacity (record the shutter sound).

You can access the digic timer from picoc directly with *(int*)0xC0242014. I think it's worth trying; the main problem here is DryOS timing resolution.

[wolf]

Just thought the most simple way might be record the machine with 25 fps or  24 fps depending on machine freq.
Extract the clip to single frames
use nth-image of the result and
create a new clip with them.

You also could use FPS override to adjust the sync time.

[scrax]

So, in order to get a 25p video of 1 machine cycle, you will record 25 timelapses, each at 1 image/second, and then assemble them in a movie?

Yes, to explain it better here there is a controller made for this purpose: http://www.bmumford.com/photo/synchronome/index.html
I took the idea from it