Using a picamera, what is the best latency one can achieve from a real world event like an led lighting up and the Pi/MCU 'knowing' it has occured(by extracting image data)?

I would also be interested in all the parameters being involved, especially those the user has control over like shutter speed.

The docs state a maximum FPS of 90, resulting in a frame time of 11ms. But that does not guarantee an actual response within that timeframe. I couldn't find any worthy mention of latency in said docs.

Setting up an experiment

The best experiment I can think of consists of

  • pi + cam
  • an LED
  • an oscilloscope

The oscilloscope is hooked up to the led as well as any digital GPIO of the pi, measuring the time between those 2 changing level.

The software on the pi shouldn't perform any more processing than let's say checking a single pixel in the center of the picture for being brighter than a dumb threshold like 200 and pulling the GPIO pin high, if it is. This way, processing power won't matter much.

  • For the timing, I'd make the Pi light the LED (in a process independent to the camera). That way you can just log the time it goes on in software, and log the time the light is detected, saving the need for an oscilloscope. – Mark Smith Mar 7 '19 at 20:47

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