Art Meets Science
Water drop photography poses two major technical challenges. First, water drops fall very rapidly, and the splashes they make on impact move even faster. A normal photograph of fast-moving water will be very blurry. To freeze the splash, the photographic exposure must be very short; around 100 microseconds. But no camera shutter can operate that quickly. The only way to get such a short exposure is with a very brief pulse of light. Modern flash units put out suitably short pulses if their power is turned way down. If the only light the camera sees is from the flash, the shutter can be left open while the drop falls and the splash forms, then closed after the flash goes off. The part of the splash you see depends on exactly when the flash fires. Second, clear water is very difficult to photograph, and it is not all that interesting to look at except from a scientific perspective. If color is added to the water, or to the light, the splashes show up much better and are more interesting to look at.
The scientific part of water drop photography is control of the process from when a droplet of water starts falling to when the camera records an image. I use an electronic valve to release a single droplet of water. The falling drop triggers a photocell, which starts an electronic timer. At a predetermined time delay, the flash is fired and the image recorded by the camera. The timer lets me control when the flash is fired. If the flash fires very soon after the drop hits the pan of water, the splash will have a crown-like shape. If the flash is delayed a few hundred milliseconds after the initial impact, the splash will look like a tall spike. If a second drop is released at just the right time, it will collide with the tip of that spike and produce a mushroom-like shape. The shape of the splashes continuously changes as they first form, rise, and then fall back into the pan. Timing of the flash lets one control which shape gets photographed. There is also an element of randomness at work. No two splashes are ever the same, even if the timing is unchanged.
The artistic part of water drop photography is experimenting with the color and chemical properties of the liquids, and with the timing and color of the light from the flashes. The splash shapes are influenced by how far the drops fall and by the depth of liquid in the pan they fall into. Shallow depths result in better crowns; more depth results in better spikes. The splashes can be made taller by reducing the surface tension of the water. The ripples can be smoothed out by increasing the viscosity of the water. Colored dyes in the pan or in the drop result in a mixture of colors in the splash. Different colored filters over the flashes also add color to the splashes or to the background. Combining these factors to create images is an art form, similar to a painter who uses different colors of pigments to create an image.
Photographic Image Processing
The images in the Photo Gallery are real. They are not digitally created. I touch up the images to adjust exposure, remove noise specks, or to crop away parts of the background.
Historical Note on Capturing Water Drops
High-speed flash photography has been used by scientific experimenters since the 1850s to capture images of the splashes made by falling drops of water. The development of the xenon flash tube in the 1930s by Harold Edgerton of MIT was one of the major drivers of modern high-speed photography. More recently, the availability of portable flash units, digital cameras, and microcomputers has brought high-speed photography out of the laboratory.