Design Nomenclature / Light & Optics
Spot light
Also called spot, cone light
A source constrained to a cone, with a hot centre falling to a soft edge across a controllable penumbra angle. The cone is a masking of direction, not a property of the emitter: within the beam, falloff follows whatever law the underlying source already obeys.
Not to be confused with
- IES profileMeasured photometric data for a real fixture, tabulating luminous intensity in candela across a grid of angles. A renderer reads it to reproduce that luminaire's actual beam — the scallops, the cut-offs, the side lobes — instead of an idealized cone. It carries distribution and total flux, not spectrum.
- Point lightAn idealized source of zero extent radiating equally in all directions from a single position. Because it has no size it subtends no solid angle, so it casts geometrically hard shadows with no penumbra whatsoever, and its illuminance obeys the inverse-square law exactly rather than approximately.