I have been asked on several occasion to explain the technique behind my droplet photos. While this is nothing new and the technique has been reviewed elsewhere before I thought I would provide a quick tutorial
The beauty of this type of photography is that it provides endless creative possibilities in the confines of your own home. This is very helpful when the days get short and the skies are gloomy.
To focus the shot you needed to use manual focus. You can manually release the droplet to impact on the surface of the water but you need to find a way to consistantly land the drop on the same spot. If you are off by even a few millimeters the droplet will not be well focused. The best method I found was to build a frame out of household materials -wood, pvc pipe etc, and then clamp a plastic cup to the frame. If you use a tiny pin to poke a small hole in the bottom of the cup you can get small droplets to fall from the cup as a usable interval ( say 1 drop every second or two). I have since gotten a little fancier using syringes and tubing but that's not necessary if you're just getting started. Once you've established your impact point, place an object ( I like to use a large deck screw - the threads provide a good surface to focus on) at the point of impact and prefocus the camera.
The trick to getting sharp photos lies not in the speed of the shutter but in the duration of the flash. If you really want sharp dropelt photos, you need a good (but not necessarily expensive) external flash. My shots were mostly taken at shutter speeds of 2-3 seconds. I usually set the shot up in my basement where I can get near dark conditions ( and no interuptions). I leave enough light so I can see when the droplet is released and then trigger the flash. Flash duration is tied closely to flash power. If you use the flash at maximum power the flash will last longer. Conversely if you turn the power all the way down you will get a very short flash duration. I purchased an old Nikon SB28DX on Ebay for about $35 just for this purpose. When the power is set to minimum the flash duration is about 1/50,000 second. This is much shorter than the 1/2,000 sec shutter speed that most cameras are capable of. In the micro world of droplets that small amount of time can be the difference between an OK photo and one that freezes the action tack sharp.
If you really get serious about this you can use an electronic photogate to trigger the flash. I built one from a kit purchased online for about $20. A photogate is an electric eye which is set up so that when the droplet passes by, the flash is triggered after a short delay. An adjustable delay is essential for this type of work as it allows you to capture different parts of the sequence. The photogate lets you to time things more precisely and reproduce your results more accurately.
Experimentation makes this process so interesting. Colors can be added to the scene by using colored liquids or placing colored objects in or around the water. Different effects are genereated depending on the depth of the water, the temperature of the water, the height of the droplet release and many other variables.
The key is to keep experimenting and have fun.