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Luminaire luminous flux Llm

The luminaire luminous flux (Llm) defines the usable light of the luminaire and is the decisive value in lighting design. As opposed to the lamp luminous flux (lm), the luminaire luminous flux (Llm) accounts for losses due to the design of the luminaire. SCHMITZ | WILA defines only the Llm value for all LED lamps. This value can be found both in data sheets and in the relevant EULUMDAT file.


System efficiency Llm/W

System efficiency defines the ratio of luminaire luminous flux (Llm) to power input (W). Efficiency losses due to gear boxes have already been taken into account in the Llm/W value.


System photometric data

For a qualified comparison between LED luminaires and luminaires with compact fluorescent lamps, it is important to ensure first that the products to be compared share approximately the same photometric data. Sample calculation:

LED luminous flux 2000lm (100%) - system losses (light output ratio) = luminaire luminous flux 1720Llm

LED efficiency 2000lm : 15W = 133lm/W

System efficiency 1720Llm : 17W (15W LED module + 2W driver) = 101Llm


Cut-off angle

The cut-off angle of luminaires is defined as the angle between the horizontal plane and the point from which the light source is not directly visible yet. The increased visual comfort offered by shielded light sources is clearly perceivable. The Downlights of the ALPHABET ZONO family of products, for example, have a very good cut-off angle of 30°.


Half-peak divergence angle α

For accent lighting, the half-peak divergence angle α is given rather than the beam spread angle. The half-peak divergence angle is defined as the angle of the rotationally symmetrical luminous intensity distribution at which the luminous intensity equals half of its maximum value. The half-peak divergence angle is given as a full angle.

super spot

< 10°


10° - 20°


21° - 45°

wide flood

46° - 55°

very wide flood   

> 55°


Number of luminaires

The number of luminaires (No. Lum.) is an approximate planning factor that can be used to calculate simply and quickly the actual number of luminaires necessary to provide a room with an illuminance of 100lx. The values are based on a surface of 100m² (room ratio 2:3) and a room height of 3m. The reflectances used are 80/50/20% (ceiling, walls, floor) and the calculation is based on a maintenance factor of 0.8. The approximate number of luminaires can be calculated using the following formula: nominal number of luminaires = room area in m² x Em in lx x number of luminaire / (100lx x 1m²).

Calculation example number of luminaire: The aim is to determine the number of lights necessary to attain an illuminance of 500lx in a 50m² room. The table for the chosen light states number of luminaire = 0.07.
This produces the following: 50m² x 500lx x 0.07 lights / (100lx x 1m²) = 17.5 ≈ 18 lights.


Beam spread angle γ

The beam spread angle γ is defined as the angle at which the luminous intensity drops to 1% of the maximum value lmax. It is measured from the vertical (see luminous intensity distribution curve) and is an important dimension in glare reducing measures.

Limits of the average luminance of screens with a beam angle of > 65°


Screen high
Illuminance ≥ 200cd/m2



Screen average
Illuminance ≤ 200cd/m2



Positive polarity and
usual requirements 1)

≤ 3000cd/m2



 ≤ 1500cd/m2



Negative polarity and
high requirements 2)

≤ 1500cd/m2



 ≤ 1000cd/m2



1) Example Office programme, dark text on bright background
2) Example CAD programme, bright lines on dark background



The UGR method takes into account the layout of the luminaires in the room and evaluates the glare produced by the entire lighting system for a specific observer‘s position. WILA provides UGR values where the observer’s position is parallel to the longitudinal axis of the luminaire and the lamp/luminaire axis is parallel to the longer side of the room. The UGR method is implemented on the basis of simple tables. A low UGR value indicates that glare is negligible or non-existent.

Suitability examples maximum UGR values:

16  for drafting rooms,
19  for offices and control rooms,
22  for precision industrial tasks
25  for light industrial tasks and
28  for heavy industrial tasks.


Luminous intensity distribution

In order to give a clearer overview, the luminous intensity distribution curves have been divided into groups. Shown are the planes from 0° to 180° (red line) and from 90° to 270° (blue line). The 0° plane is on the right.


Beam chart

For accent luminaires beam charts are shown. The angle of the spread out beam corresponds to the half-peak divergence angle of the luminous intensity. Diameter and mean illuminance Em [lx] can be read from the chart for each corresponding height.


Planning grid room

The chart is intended as a means of calculating the approximate illuminance required for ceiling grids in rooms and corridors. For the 600 grid, the illuminances should be multiplied by a factor of 0.9.



-DV = Loop-in/Loop-out
-DD = dimmable, DALI
-DD-DV = DALI dimmable with loop-in/loop-out function
-PT = integrated luminaire controller with daylight control and presence detector
-BTC = Smart Lighting light management integrated
-BTC = Smart Lighting light management integrated with loop-in/loop-out function



OH = overhang, max. expansion of luminaire from the centre of reflector
W, W1 = width information
D = diameter
CO = ceiling, wall or recessed floor cut-out
CO W = width of ceiling or wall cut-out for recessed luminaires
CO L = length of ceiling or wall cut-out for recessed luminaires
RD = required installation depth for recessed luminaires under consideration of F conditions
H, H1 = height information
K = colour temperature in Kelvin
L, L1 = length information
Q = reflector size, square
R = reflector size, round
Ra = colour rendering index
W = electrical power
α = half-peak divergence angle
γ = beam spread angle