SSL V5.0 and V5.1 Definitions

Definitions of terms needed to understand SSL Technical Requirements V5.0 and V5.1. To view the full Technical Requirements documents, click here. General Definitions
  • Technical Requirements Tables (TRT): The Technical Requirements Tables are a complete set of minimum technical specifications that products must meet to be qualified on the DLC QPL. TRTs can be found on the DLC website.
  • Parent Product: Products for which tested data, including lumen output, efficacy, UGR (if applicable), and BUG rating (if applicable) are listed on the QPL. Note that these products have both tested and reported data.
  • Child Product: Products for which tested data is not listed on the QPL.
Controllability Definitions
  • Dimmable: a product that (a) includes a dimmable driver and/or is capable of being dimmed by an external control signal, and (b) is identified as dimmable on the product specification sheet. Products that meet this definition are considered to meet the dimming capability requirement.
  • Continuous Dimming: Per NEMA LSD-64: a lighting control strategy that varies the light output of a lighting system over a continuous range from full light output to a minimum light output without flickering in imperceptible steps. Continuous dimming shall be capable of reducing the light output to at least 20% of full light output.
  • Stepped Dimming: Per NEMA LSD-64: a lighting control strategy that varies the light output of a lighting system in one or more predetermined steps of greater than one percent of full output. The changes between levels are generally perceptible. Stepped dimming shall be capable of reducing the light output to at least 70% of full light output.
  • Integral Controls: The capability to have sensing and/or control of light output directly integrated or embedded into the lamp or luminaire and available as an option within the lamp or luminaire product model number.
  • Control Communication: The method and capability of a lighting system to receive and implement commanded changes to the operation, dimmed state, color setting, timing, etc.
Spectral Quality Definitions
  • Spectral Power Distribution (SPD): Describes the power emanating from a light source as a function of wavelength. The information can be presented graphically or as a numerical table.
  • Color Rendition (of objects): Effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant.
  • Chromaticity: The aspects specified by the chromaticity coordinates of the color. It describes the color of the emitted light, independent of its intensity.
  • Duv: A signed measure of the distance from the blackbody locus in the CIE 1960 (u, v) color space. A positive Duv indicates that the chromaticity of the light is above the blackbody locus (on the green side). A negative Duv means the chromaticity is below the blackbody locus (on the blue/pink/purple side).
  • Correlated Color Temperature (CCT): The thermodynamic temperature of a blackbody whose chromaticity most nearly resembles that of the light source. Expressed in Kelvin (K).
  • Color Maintenance: A product’s ability to maintain a specific chromaticity over time. This is the spectral corollary to luminous flux maintenance, which describes depreciation in luminous flux over time.
Light Distribution and Discomfort Glare Definitions
  • Discomfort Glare: Glare that produces discomfort. It does not necessarily interfere with visual performance or visibility. Other definitions of discomfort glare include:
    • A sensation of annoyance or pain caused by high luminance in the field of view. Four factors are known to participate in the perception of discomfort glare: luminance of the glare source, size of the glare source, position of the source in the field of view, luminance of the background (10th edition of the IES Handbook, Chapter 4.10.1.)
  • Unified Glare Rating (UGR): A measure of the discomfort produced by a lighting system along a psychometric scale of discomfort.
    •  The Unified Glare Rating formula is a discomfort glare likelihood assessment method developed, published, and recommended by the CIE in 1995. The UGR formula produces a glare rating which is a psychophysical parameter estimating the discomfort in response to glare in a visual environment containing light sources. The practical UGR range is from 10 to 30 with most lighting systems producing values in that range. A high value indicates likelihood of significant discomfort glare, while a low value indicates little likelihood of discomfort glare.
    • The development of UGR predated the application of LEDs in general lighting, and studies have reported that the original UGR formula tends to underestimate the discomfort sensation provoked by the highly non-uniform source luminance from some LED luminaires. A correction term to the original UGR formula was consequently formalized in a CIE report in 2019 taking into consideration the effects of non-uniform glare sources.16 Due to the recency of this new development, UGR in the remainder of this policy refers to the 1995 UGR formula, and the DLC will consider adopting UGR with the correction term in future updates when standards are available.
  • Uncorrected UGR Table: A set of UGR values of the luminaire tested based on pre-set room definitions and a luminous flux of 1000 lumens, as defined in CIE 190-2010. The data are provided for 19 standard room shapes with 5 different combinations of room surface reflectance. For application of the uncorrected UGR table, the values must be corrected to the actual luminous flux in the luminaire.
  • Corrected UGR Table: A set of UGR values presented in the same format as the uncorrected UGR table with the same pre-set room definitions but corrected using the total luminous flux of the luminaire.
  • BUG Rating: The IES Luminaire Classification System (LCS) that defines the distribution of light from a luminaire within three primary solid angles: forward light, backlight and uplight. These are further divided into ten secondary solid angles as described in IES TM-15-11. The BUG rating is then determined using Addendum A for IES TM-15-11 according to a luminaire’s lumen output within the secondary solid angle zones as defined in the document.
  • Bare Lamp: the performance characteristics of a replacement lamp when operated outside of a luminaire or retrofit kit, including the effects of an external ballast (for Type A and Dual-Mode lamps) or driver (for Type C lamps).
  • (Bare Lamp) Beam Angle: The angle between the two opposite directions in which the average intensity is 50% of the center beam intensity as measured in the azimuthal plane perpendicular to, and at the center of, the linear replacement lamp axis.