Optics is where I usually start when I want to reason about a light-based system at human scale. It is the layer where lenses, imaging paths, apertures, aberrations, and system tradeoffs become concrete enough to think about clearly.

What I want this tag to emphasize is physical intuition: what bends, what focuses, what blurs, and which part of the system is really driving the behavior you care about.

A good place to start:

• Optics: Imaging, Refraction, and Systems
• More on Optics

Closely related tags include Photonics and Colors.