Author Topic: Precise Timing of rapid fire external trigger  (Read 1614 times)


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Precise Timing of rapid fire external trigger
« on: March 23, 2017, 12:37:10 AM »
I have an application where I want to shoot at 4+fps, but I need to control the trigger of each image within +/- 2 mseconds.    If I lift the mirror and use external trigger, I can accomplish the precision, but it takes 312ms between each shot and the mirror goes down after each image.  Is there a better way to accomplish this through ML using bracketing?    I'd like to get under 250ms between images.  Can I lift the mirror and keep it lifted for four images?

The application is a rotating plate that has 4 different bandpass filters.  On every 2nd or 3rd rotation of the plate I want to capture a series of images, one for each filter.   I want to keep the filter plate turning at constant rotational velocity.  My camera I plan to use is a Canon 6D.


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Re: Precise Timing of rapid fire external trigger
« Reply #1 on: March 23, 2017, 01:44:06 AM »
Not with current implementation, unfortunately.

You can lift the mirror and keep it lifted with a piece of tape; however, the mechanical shutter is actuated. This part happens on a different CPU that is not very well understood (the MPU). You can take pictures with shutter open (see FRSP), but has a gradient at short exposures. Additionally, file saving and image capturing must be pipelined to achieve 4 fps.

If resolution and rolling shutter are not an issue, you could look into half-shutter triggers for raw recording. However, its timing is given by the LiveView clock, not by the external trigger.

Delaying pictures in regular burst mode using an external signal might be easy to implement (didn't try, but I don't see why it wouldn't work). Not sure if half-shutter can be used as a sync signal though, as it must be pressed to keep the burst running.