Waterdrop collision

This is a picture of two water drops colliding with each other. Two drops of water were released with a specific time differential between them. The first drop hit a pool of water and bounced up to collide with the second one. I used two flash units placed on either side of the setup, one with a red gel filter and the other with a cyan filter. The falling drops triggered the flash units, and the lights in the room were dimmed enough so they didn't influence the exposure but offered enough light for me to see what I was doing. The total exposure time was 2.5 seconds, and I used f/32 to gain as much depth of field as possible. I did several test shots to determine the exposure, and I varied the amount of light striking the location where the drops collided by positioning the flash units closer to and farther from the water. The ISO in this shot was 800. With the device I was using (Cognysis Stopshot), I was able to alter the timing between the two drops in thousands of a second in order to orchestrate the collisions.