I wanted to know the delay from closing the shutter of my camera to when the actual picture is taken. With this information, then it becomes easier to setup various stop-motion picture captures.
For this experiment, I needed three things:
- A way of controlling the Canon XSi camera
- A bright enough LED with a short flash time while the camera was in total darkness
- An accurate accounting for delay from control of camera to LED flash
The LED I used was a Luxeon I, which was controlled via a simple transistor driver (2N2222 + base resistor). The flash time for the LED was chosen to be only 1msec. To get an accurate delay I found I had to write my own delay routines. The delay routines provided by the Arduino library were not really adequate for my purpose.
My software hardware algorithm was simple. Have the arduino close the camera shutter, have it delay a predetermined (but user variable) amount, and flash the LED at a piece of paper, for which the camera was taking a picture. I then manually looked at the resulting picture to see the amount of light that was exposed in the picture. I recorded the results and changed the amount of delay and repeated. Because the LED flash time was only 1msec, I had to shoot with an ISO of 1600.
I did two different sets of pictures. The first picture set was just of an arbitrary piece of paper I had laying around. It had some garbage writing on it, but this was to determine if the setup worked ok. The shutter speed was set at 1/100. I approximated from these pictures the actual shutter speed at 1/100.6, which is within 0.6% of the camera’s setting. Also the delay begins at 84msec through 86msec depending upon the position in the camera’s sensor.
Notice how the sensor is opened from the bottom and the 2nd curtain also starts at the bottom (as it should).
The second set of pictures was of a sheet of paper that had printed on it lines labelled from 0 through 10. This ruling would permit me to better estimate the delay time to % position of the shutter open or closed. I carefully positioned the paper and camera zoom so that the “0” line was just at the bottom and the “10” line was just at the top of the camera’s sensor.
Here is an example of one of these shots.
Lastly, I used the perceived % opening/closing of shutter to plot the delay of the shutter. I posted these as two excel charts, the first for the shutter opening, the second for closing.