Humble Beginnings for Water drops
I highly recommend the new MKJZZ Water Drop Kit which is now my water drop system of choice.
I accidentally erased my original explanation on this, but I will replace it with one that's even better.
I started out doing drops using this method for about a year and have had much success with it. It is not easy getting the timing down, but with experience, it gets easier. Success rate is about one in ten for a two drop collision.
With this camera, a Canon 450D, I used a remote shutter cable and used the timer for the shots. I would get to know the sound of the beeping on the camera when to release the drops just before the shutter would open. The timing is critical and it takes quite a while to get it right.
I used a regular medicine dropper. The size you see in the picture is good for drops. I didn't like the smaller ones, because the drops are then smaller as well. You need to gently squeeze out two drops very close together (perhaps about 1/4 inch apart to get the two drop collision. Too close together and your drop will be very short, and too far apart and the second drop will not have had time to connect with the first one coming up out of the water.
If you squeeze too many drops out of the dropper, it will just be a mess, however, you will get some unique creations this way as well.
The density of the liquid you use is a great factor in producing good shapes. Water straight out of the tap is not dense enough. Very cold water is best. To thicken the liquid, use a bit of glycerine to the drop liquid. Now I use xanthan gum or guar gum which are excellent thickeners to slow down the reaction of the liquids. Mix a tiny bit with water, mix well with a blender and strain with a coffee filter. If it takes too long to strain, simply dilute with more water.
The water in the catch container has a lot of surface tension and to get higher jets for the drops, you need to use a surfactant to reduce this surface tension. One way is to use two or three drops of rinse added to the water in the container below. You can also try dish detergent, but only certain kinds will work. Using rinse aid or detergent will cause bubbles on the surface of the water, but just simply blow these away to get a clean water surface.
One of the best liquids in starting out is milk. Anything from skim milk to whole milk will do. It has the right consistency for drops. The density is perfect for good collisions.
For colouring, I use regular food dye which is available in most grocery stores. It mixes well with milk or water.
For lighting, you can use just your pop-up camera flash if necessary, but external flashes will give better results. I have the flash quite close to the drop in the picture, but if you have lighter backgrounds, you can have it back a bit farther. Try to get some of the flash directed toward the drop and the background as well. Lighter backgrounds are much better. The light bounces off the background to light up the splash as well.
You can also use coloured gels on the flashes. I used coloured pieces of plastic used for binder separators in school supply departments. This will give some cool effects on milk or water as well.
A bit about Flash Exposure Compensation. It is the low power of the flash which freezes the motion, not the exposure of your shutter. You will need to check your camera and find the flash exposure compensation setting and bring it down quite a bit. If it is too high, you will get a lot of motion blur on the drop. If you bring it down, you will get less light, but the speed of the flash is so quick, it will capture the drop without any blur.
Camera settings: With this type of set-up, I would set my camera exposure to sync with the flash, which would be 200 or 250. You can set is as low as you want, but it won't make any difference except to let more ambient light in, which is not desirable. The low power of the flash is about 20,000th of a second, so you see it is the flash which freezes the drop, not the shutter speed. I like my aperture around 14 to 18 if possible to get as much of the drop in focus if possible. This cuts out a lot of light, however, with a lot of cameras now, noise isn't as much of a problem with higher ISO settings as it used to be. I would use an ISO of 200 or more to give you more light.
Distance between dropper and water tray can be anywhere from 30 to 50cm.
For focusing, place something on the spot where the drop will land and focus on that. A socket wrench extender, ruler, serrated bread knife, anything you have handy will do. Try to put your focus on the front half of the splash. You won't get everything in focus, but the best area is the front where your eye goes.
Another manual method you can use is the steady drip method which I explain in my book. I used a flexible plastic tube with an air regulator from a fish supply store. The air regulator controls the rate of flow. You need to have the drops about 1/4 inch apart and hold a cup underneath. Remove the cup and the first two drops make the collision. Use a shutter release cable to activate the shutter at the right moment the drops hit the water. Again, this is trial and error (mostly error) to get the timing right, but it's a good way to try drops before spending a lot of money if you're not sure you want to get into this genre of photography.
I explain much more in my book. I use a lot of pictures for reference. It contains a ton of information and well worth the purchase.
Comprehensive Water Drop Photography Guide on DIYPhotography .