When it comes to getting started in photography, one of the most complicated things for people to wrap their heads around is "stops of light." This phrase only leads to more confusion when paired with the aperture numbers, shutter speed, ISO, and how they form the mysterious exposure triangle. But this is the easiest way I have seen to understand it all.
In this video, Rob Hall walks through what exactly is happening when you adjust aperture, shutter speed, and ISO. But he does so in a way that is easy to follow and understand. Normally, when talking about these elements, you are referencing light. But because light is invisible as it flows through a scene, it's hard to really understand what's going on. So, Rob uses water as a way to visualize exactly what's happening.
Not only does this visual representation make it easy to understand stops of light and the exposure triangle, but Rob also uses glasses of water and a hose to easily explain the inverse square law, adding flash, flash power, and how they all relate to one another. So, if you are a beginning photographer or even just want to drive home your understanding of these technicalities, this is the video you want to watch.