#9. "RE: Aperture, Shutter, ISO, and Illumination Relationships" In response to In response to 0
Having taught quite a few students myself, I tend to teach the three corners of exposure first. Normally illumination is a non-variable, or at least a not often changing variable, out of control of the shooter. Only in studio environments do photographers have complete control over illumination. In outdoor settings, the sun can go behind clouds, or one can walk into shadow. You can adjust to the illumination and modify or supplement it, but never fully control it.
In my experience many struggle mightily with the concept of the three controls for exposure they have immediate control of. It is not good to introduce outside-of-camera complexity at the time when they are learning a rather complex in-camera relationship.
They can control what their cameras offer them: shutter speed, aperture, and ISO sensitivity. However, their cameras offer them no illumination control and unless they have a flash mounted or are carrying a reflector, it is often best to just teach them how to adapt to the current illumination with their camera controls.
Later, as they come to understand how the camera works within the current illumination, they can learn to modify the illumination with strobes, reflectors, modifiers, and positioning.
In a classroom (textbook) environment I can see how teaching all four at once might help. However, in that environment one is dealing with theory. In real life, with real people struggling to understand a complex relationship within the camera itself, it is not good to introduce outside variables. That comes later when the camera is fully understood.