According to those who study the microphysics of raindrops, there is an amazing complexity in the size, shape and velocity of rainfall. This kind of information can be found in meteorological journals. I became interested in recording the size and location of raindrops on my own.
I used water sensitive paper manufactured by a Swiss company named Syngenta. The paper arrives a beautiful vibrant yellow, and maintains this color as long as it is dry. When it is exposed to water, the paper turns blue through chemical reaction. After doing some tests with a DSLR, I realized that I could use video to record the paper as I exposed it to rain. From this information, it is possible to work backwards and hypothesize about how big each drop is, when it landed, how fast it was going, and where it might have been in the air before it landed.