Near-field and far-field measutrements
Near-field and far-field measutrements
(OP)
Could anyone give a good definition of near-field and far-field photometric measurements and their use.
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Near-field and far-field measutrements
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RE: Near-field and far-field measutrements
for lighting, usually 5 to 10 times the maximum dimension of the source is often used as the transition from near to far-field
TTFN
RE: Near-field and far-field measutrements
RE: Near-field and far-field measutrements
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.
Make sense? Hope that helps.
RE: Near-field and far-field measutrements
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?