Glossary

The angle at which light spreads from a source, measured in degrees. A tight beam angle (20°–40°) concentrates light for long-distance illumination; a wide beam angle (100°–180°) washes a large area evenly for task lighting and work-site setup. Narrow beams throw further but cover less; wide beams cover more but can't reach as far.

Most professional work lights sit between 60° and 120° depending on their primary use case. The right beam angle matches the job — inspection calls for narrow, area setup calls for wide.

The nominal voltage of a cordless tool battery pack, measured in volts. Professional cordless tools cluster around three tiers:

• 12V MAX — compact tools, short runtime, light-duty use
• 18V / 20V MAX — the main professional class (same 5-cell Li-ion architecture, different branding)
• 40V–60V — outdoor power equipment, high-draw tools

“18V” and “20V MAX” refer to the same physical battery — 18V is the nominal average voltage under load, 20V MAX is the peak voltage when fully charged. They are electrically identical and interchangeable.

Correlated Color Temperature describes the perceived “warmth” or “coolness” of a white light source, measured in Kelvin (K):

• 2700K–3000K — warm white, like incandescent bulbs (residential feel)
• 4000K–4500K — neutral white (offices, retail)
• 5000K–6500K — cool/daylight white (job sites, inspection, detail work)

Job-site and inspection lighting uses 5000K–6500K because cool-white improves visual contrast for reading wire codes, spotting defects, and detail work in low-ambient conditions.

A common-usage synonym for CCT (Correlated Color Temperature). Describes whether a white light source appears warm/yellow or cool/blue, measured in Kelvin. Lower numbers are warmer (incandescent-like), higher numbers are cooler (daylight-like).

See the CCT entry for the full technical definition, typical ranges, and how to pick the right color temperature for professional work.

CRI measures how accurately a light source renders the true colors of objects compared to natural daylight, on a 0–100 scale:

• CRI 60–70 — cheap LEDs. Distorts skin tones, wire colors, and paint finishes. Good enough for a parking lot, bad for detail work.
• CRI 80+ — professional baseline. Required for electrical work (wire color codes), automotive paint matching, and quality inspection.
• CRI 90+ — studio / medical grade. Overkill for most job sites but useful for color-critical work.

R9 is a supplementary metric that specifically measures red rendering — important for skin tones, automotive, and safety inspection. A CRI 80 light with R9 < 10 still renders reds poorly.

Unwanted radio-frequency noise emitted by electronic devices that can interfere with other equipment — radios, two-way communications, medical equipment, and sensitive instrumentation. Poorly designed LED drivers emit significant EMI in the 30 MHz–1 GHz range, which is why regulators require EMI compliance testing for all consumer electronics sold in major markets.

In the United States, the FCC Part 15 rules set EMI limits. In the European Union, the CE EMC Directive performs the same role. Both require independent lab testing against defined emission thresholds.

Rapid fluctuation in LED brightness, usually invisible to the eye but measurable. Caused by cheap PWM (pulse width modulation) dimming that switches the LED on and off hundreds of times per second. Even when the flicker is too fast to consciously see, the brain registers it as strain — which is why cheap LEDs cause headaches and eye fatigue on long shifts.

The IEEE 1789 standard defines a “no observable effect” threshold of approximately 5% modulation depth. Above that, human vision starts to pick up physiological effects even if the flicker is conscious-invisible.

Excessive brightness in the field of view that reduces visual comfort and performance. Two types matter for job-site lighting:

• Disability glare — actively impairs the ability to see, forcing the eye to adapt away from the task
• Discomfort glare — causes squinting, eye strain, and fatigue over long shifts

High-quality work lights use diffusers, optics, and housing geometry to direct lumens onto the task surface instead of into the worker's eyes. Raw lumens without glare control is not a win — it just moves the problem.

A two-digit code defined by international standard IEC 60529 that describes how well a sealed enclosure resists intrusion of solids (first digit, 0–6) and liquids (second digit, 0–9). The most common ratings on professional work lights:

• IP65 — dust-tight, protected against low-pressure water jets (rain, hose-down)
• IP66 — dust-tight, protected against high-pressure water jets (storm response, pressure washing)
• IP67 — adds temporary submersion (1 meter for 30 minutes)

Higher is not always better — IP67 submersion rating costs more and is overkill for most construction and inspection work, where IP65 or IP66 is the practical pro-grade target.

An IES (Illuminating Engineering Society) standard that defines how to measure the absolute photometric performance of a complete LED luminaire — total lumens, luminous efficacy (lm/W), chromaticity, color rendering, and beam distribution.

LM-79 testing happens in an accredited photometric lab using integrating spheres and goniophotometers, producing a signed report that the manufacturer can submit for certification or publish as proof of spec. “LM-79 tested” means the advertised lumen output is verified by a third party — not marketing.

An IES standard that defines how to measure the long-term lumen maintenance of individual LED packages (the chips — not the finished fixture). Labs run LED chips at controlled temperature and current for 6,000–10,000 hours while measuring light output decay, producing “bin” data the luminaire manufacturer uses to project useful life (L70/L80/L90).

Important distinction: LM-80 is a chip-level binning standard, not a finished-product certification. A complete work light cannot be “LM-80 certified” — only its underlying LED chips can be LM-80 tested. Beware of brands that list LM-80 as a certification they hold.

The SI unit of luminous flux — the total amount of visible light a source emits per unit time, weighted by human eye sensitivity. Reference points:

• Standard 60W incandescent bulb — about 800 lumens
• Bright consumer flashlight — about 1,000 lumens
• Professional work light — 3,000 to 12,000 lumens
• Automotive headlight — 1,500 to 2,500 lumens per bulb

Note that lumens measure total output, not brightness per area. For actual brightness at the task surface, see Lux.

The percentage of initial light output a luminaire still produces after a given number of operating hours. Reported as L70, L80, or L90 at a specified hour count — for example, L70@50,000h means “70% of original lumens at 50,000 hours of use.”

Cheap LEDs often drop 30–40% in the first 2,000 hours due to poor thermal management and low-binned chips. Professional fixtures maintain ≥90% output for 10,000+ hours through conservative driving current, aluminum heat sinks, and LM-80-binned LED packages.

The SI unit of illuminance — lumens per square meter. While lumens describe the total light a source emits, lux describes how much of that light actually lands on a surface. Reference points:

• Bright office desk — about 500 lux
• Well-lit workshop bench — 750 to 1,000 lux
• Outdoor task work in daylight — 10,000 to 25,000 lux

Lux drops off with the square of the distance (the inverse-square law), so doubling the distance quarters the lux at the task surface. A lumen-heavy light at 10 meters can deliver less usable lux than a modest light at 2 meters.

A pricing policy where a manufacturer requires authorized retailers to publicly advertise a product at or above a specified minimum. MAP protects the brand's perceived value, keeps the retail channel profitable, and prevents race-to-the-bottom marketplace pricing.

MAP covers the advertised price (website listing, ads, catalog) — retailers can still sell below MAP in person or via quote. Violations typically result in loss of authorized-seller status and removal from distribution channels.

How long a work light operates on a single battery charge, measured in hours or minutes. Runtime depends on four variables:

1. Battery capacity (amp-hours, Ah)
2. Battery voltage (volts, V)
3. Light power draw (watts, W)
4. Driver efficiency (percent)

A 5.0Ah 20V pack stores approximately 100 watt-hours, so a 25W light draws roughly 4 hours of runtime on high — before VoltShield™ cutoff. Larger packs (9Ah, 12Ah) proportionally extend runtime. Cycling between high and low modes can double effective runtime on long jobs.