My readers know I am The Wildlife Ho-tographer and have used Canon equipment for 25 years. Throughout the decades, I have tried or owned almost all of their cameras and lenses. You can see my recommendation on Canon's cameras and lens, see my equipment bag and works on MichaelDanielHo.com
The video below gives a good explanation on the history and science of lens design, manufacturing and how it had impacted photography. It is a bit long (about 25 minutes) but around the 14th and 18th minute, the video talks about the lens' place in photography and modern day lenses, respectively. The last 2 minutes explain how the Japanese lens manufacturers come to dominate the present day lens market. It's worth a look for those interested in optics and photography.