Water drop collision

I've come up with a new idea for a photo workshop, and one of the cool things I'll be setting up for participants is a device that sets up water drop collisions. Anyone can photograph a single water drop splashing into a liquid, but to be able to capture two drops colliding with each other requires practice, finesse, patience -- and a sophisticated electronic device. For this shot, I added some milk to the water to give the liquid a bit of opacity. The color comes from two flash units, one covered with a green gel and the other covered with a magenta gel. The timing device, made by Cognisys, measures the time between the release of the drops and the collision in milliseconds. I used a Canon 100-400mm lens with an extension tube to fill the frame with the collision. This picture is uncropped. My settings were f/32, 1600 ISO, and I turned the power down on the Yongnao flash units to 1/128th power. This produced an extremely short flash duration (about 1/128,000th of a second) which froze the action. The shutter speed was irrelevant in terms of exposure, but it was 2 seconds.