Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

B

The width (angle) of the light spot produced by the particular light fitting. The brightness at the outside of the “Beam” is 50% of the brightness of the centre of the “Beam”. Beam angle is similar in concept to “Field Angle”.

Light fittings with small Beam Angles are less efficient than light fittings with large beam angles. Beam Angles that are higher than 80° cause more GLARE.

B50 / B90 indicates the measured failure rate. 50 means 50%, 70 means 70%, and B90 means 90%.

Lighting with increased blue spectrum components increases alertness, but also contributes to reduced ability to sleep.

C

The approximate colour of the light.
• 3000K is relaxing and is typically used for homes, and premium retail stores.
• 4000K is comfortable for offices, retail stores, outside areas and warehouse areas.
• 5000K for warehouses and outdoors.

The colour of the light produced by lamps, including LED, changes over the life of the lamp. Most people will not notice differences between two light fittings at opposite ends of the 3SDCM ellipse, but will easily notice differences in lights that are 4SDCM. Like all light sources, LED can Colour Shift / CCT Drift over its operational life. A 3SDCM LED light fitting can end up as 4SDCM, or worse.

CRI indicates how well a light fitting generates different colour components of light. Higher CRI increases the quality of the light, but also reduces the efficacy (efficiency) of the LED chips.

The RED phosphor used in LEDs has lower efficacy than the phosphors that create other colour light. LED with low CRI have reduced RED component, and may cause a sickly tint (blue/green), however the efficacy is increased.

D

DLOR is the ratio between how much light is generated by the LED chip (or lamp) versus how much light actually comes out of the light fitting. DLOR is always less than 100%.

E

Efficacy is the ratio of Light Output (luminous flux / lumens) versus the Power Input (Watts). At time of writing LED chips are approximately 160 lm/w for CRI80 and 130 lm/w for CRI90.

Efficiency is the ratio of Output versus Input, and higher is better. When referring to Electronic Drivers, this refers to power. Typical efficiencies are 87-90% for non-dimmable drivers, and 80-85% for dimmable drivers.

F

The width (angle) of the light produced by the particular light fitting. Width of the Field angle is the width of the “beam” where the brightness is only 10% of the brightness of the centre of the light beam.

G

Glare is caused by excessive light coming out of the fitting at wide beam angles, and can cause irritation, or discomfort. Fittings with Beam Angles exceeding 80° commonly cause glare, and in large groups can cause excessive discomfort.

L

L70 is the typical lifetime rating for LEDs. LM80 testing (to TM21) notes that Useful life of LED is limited to the point that the Light Output of the LED reduces to 70%.

S

SDCM / “MacAdam Ellipses” indicate the various limits that humans can differentiate between variations in the light colour. The majority of people cannot differentiate differences up to 3SDCM.

Note that all light sources, including LED, are subject to “Colour Shift” or “CCT Drift”.