Inverse square law

I'm beginning to learn some basics of lighting. So this may well be wrong, but the physicist in me couldn't help itself.

Several of the lectures I've listened talked about the inverse square law. The problem is, it doesn't apply: or at least not strictly to the problem they describe.

The inverse square law models a point light source radiating uniformly in all directions. At a distance x from the source, the energy falling on an area y is the proportion of the power of the source of area y relative to the surface area of the sphere of radius x.

If you double the distance from the source, the surface area of the sphere at 2x is now four times as large (A=4/3Πr²) since surface area increases in r². So y is now 1/4 of the area of the larger sphere and so receives only only 1/4 of the energy emitted by the source.

But often the lighting being used and measured in the studio isn't from a point source; it's collimated with umbrella reflectors, so the energy doesn't fall off as the square of the distance. The ultimate in collimated sources is a laser; absent scattering all the energy emitter at the source hits the target. The same principle applies to theatre spot lights or search slights.  

That being said, I am guessing that for soft boxes the inverse square law is a fairly good approximation since each point on the front of the box might be considered as a point source. But in any setup in which light from the source is focused, the inverse square law won't apply.

Disintermdiation

This post probably doesn't belong here, since it's really about digital: specifically my prediction that the Internet will render prints obsolete, and with them the need for mass market dedicated cameras. Aside from some niche uses, most people will take pictures on their smart phones, and upload them directly to a website, such as Facebook, where they will be viewed; the images will never be printed from beginning (capture) to end (viewing). Smart phones are better positioned to do this than cameras since they are already connected to the net. If the highest resolution needed is that needed to view a picture on a large screen TV, then a 20+ MP dedicated camera looses out to an 8MP smart phone. I give the mass market segment of the dedicated camera industry another 10 years.