Two lamps can both claim “4,000 lumens” and perform very differently. Raw (or theoretical) lumens are taken from the LED manufacturer’s chip datasheet at ideal temperature. Effective lumens are measured at the lamp: after the lens, reflector, driver current and operating heat take their share, typically 20–40 % below raw.
Why the gap exists
Optics absorb and scatter light; LEDs dim as they heat up; drivers run chips below maximum current to extend lifespan. A well-engineered lamp manages these losses — sophisticated reflector optics waste less light and put more usable light on the task.
What to ask a supplier
Ask whether a quoted figure is raw or effective, and compare effective to effective. Where we publish both, our listings state them separately. Beam pattern matters as much as output — see beam patterns for how the same lumens serve different jobs.
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Related terms
A beam pattern describes how a lamp distributes its light: flood beams deliver wide, short-range illumination; spot beams project a narrow, concentrated beam over distance; combination beam lights provide both from a single housing.
Color Temperature (Kelvin)Color temperature, measured in kelvin (K), describes the tint of white light: around 3000 K is warm (yellowish), 5000–5700 K is neutral daylight white, 6000–6500 K is cool white. Most machinery LED work lights ship at 5700–6500 K.
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