We all have a fairly intuitive grasp of what focal length is in relation to taking photos: higher numbers mean more zoom. But what actually is the focal length of lens? This great video will show you what it is and what consequences it has on the lenses you choose and the photos you take.
Coming to you from Apalapse, this helpful video explores the concept of focal length and what it means for your photography. In terms of physics, it's the distance it takes an optical system to bring initially collimated rays of light to a point of convergence. Thus, you might think of wide angle lenses as "more powerful" in the sense that they bend the light rays more severely to make them converge over a shorter distance. However, you may also notice that some modern lenses are actually shorter than their focal length. They aren't breaking the laws of physics; rather, through the miracle of multi-element lenses and some clever design (specifically, a telephoto group), they effectively lengthen the light's path by reducing the angle of convergence after the rays have already converged partially. It's a pretty neat trick. Check out the video above for more on the topic.