With near-field there are apparently two types of measurements viz. Appliction-distance photometry and Luminance-field photometry. The first is still treated as a point source. I think this is what is confusing to me. Do you have experience with these measurements and calculations and does the inverse square rule, for illumination, have meaning here.
I'm not familiar with the terms "Appliction-distance photometry" and "Luminance-field photometry"
But if it's point source, then light falls off with the cube of the distance, as it dissipates spherically.
If your close to a fluorescent tube, though, the light would dissipate cylindrically. That would lead to inverse-square instead.
If you had a large planar source, the light would remain constant in near-field.
However, as you get further away from any source, it will eventually look like a point and therefore the light will eventually start dissipating inversely to the cube of the distance again.
Hello peebee,
Thanks for your reply. The terms I refer to are in the 9 th edition of the IESNA reference under the heading "Near Field" or from the index on near field.
I have not heard that illumination (Lux) was proportional to the inverse cube but certainly to the inverse square of the distance for a point source. What light measurements are you refering to for a sphere and cylinder? Are you refering to the surface area of a cylinder and sphere?
