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| p.4 #9 · silly inverse square law question. |
1. Light is energy
2. Conservation of energy states that energy can be neither created nor destroyed (i.e. it only changes form)
3. Unless something acts upon that energy to change its form, it will retain its form and magnitude
When light is traveling it will continue to have the same amount of energy until it interacts with another object. Upon striking an object, a portion of that energy will be absorbed (giving us subtractive color) and a portion of the energy will be reflected (or refracted to continue through a transparent or translucent object).
The energy that is neither absorbed, nor refracted will be reflected in iaw with AI=AR and that remaining value of energy will continue until it is acted upon by another object that it is acted upon (i.e. the lens refraction / reflection) and subsequently reach the sensor where it its energy gets absorbed and changed into an electrical signal.
A point light source releasing energy does so in accordance with path of least resistance, which is theoretically none, and as such the distribution and transfer of the amount of energy will be distributed in a spherical manner resulting in a trigonometric distribution of that energy iaw with ISL.
Once that energy has been given a direction, it will continue along that path indefinitely until acted upon by another object, which includes absorption, refraction and reflection ... all of which are vector quantities that are responsible for the degree of form & direction change that occurs from the available energy.
The concept that you are trying to apply ISL to reflected energy via camera to subject distance is simply not true. You are wrongly applying the dispersion / distribution of a point light source that is omni-directional at it's origin to directional light that continues to follow AI=AR (absorption & refraction) to infinity, iaw with conservation of energy.
Take a laser pointer and you can more readily see that light does NOT travel iaw with ISL. It does NOT spread iaw with ISL. It does NOT diminish iaw ISL.
Sure, the pointer is not full spectrum, and has been given "direction" ... but every ray of light that is emanating from a point light source also has been given a "direction" (i.e. spokes on a wheel). The collection of rays emanating from a point light source is an omni-directional distribution of the energy released from the point light source ... but it continues in a directional manner iaw with AI=AR and the energy contained for a given ray remains unchanged until acted upon by another object. Diffuse light simply being a collection of incident angles and/or reflecting angles that collectively cover a wider angle, whereas specular light is limited to a more narrow coverage.
ISL is a trigonometric calculation of the distribution of the energy released. The absorption, refraction and reflection of light continues directional iaw AI=AR and vector forces ... iaw with conservation of energy ... not predicated upon ISL & offsetting camera to subject distance.
Edited on Nov 06, 2012 at 10:11 PM · View previous versions