Why calculate lighting before ordering fixtures?

A fixture catalogue shows wattage, lumen output and optics, but it does not tell you whether a real room, dome, facade or exhibition wall will receive the required light. Calculation software uses the actual geometry, mounting heights, surface reflectance and photometric data of the selected luminaires to predict the result before installation.

Typical inputs

• DWG/DXF or PDF plans and sections
• Ceiling, dome or facade heights
• Room dimensions and surface materials
• Desired lux range by activity or zone
• Mounting points and aiming constraints
• IES or LDT photometric files
• Maintenance factor and environmental conditions
• Daylight information where relevant

Core outputs

• Average, minimum and maximum illuminance: measured in lux.
• Uniformity: how evenly light is distributed across the target plane.
• False-colour maps: quick visualisation of light intensity across floors, walls or architectural surfaces.
• Isolux diagrams: contour lines showing areas with similar illuminance.
• Luminaire quantity and position: a defensible basis for fixture count.
• Aiming plan: especially important for spotlights, projectors, domes and facades.
• Connected load: total wattage and control-zone planning.
• Glare review: where the application requires UGR or other glare assessment.

DIALux and Relux workflows

Both workflows can be used to model interior and exterior spaces with manufacturer photometric data. The important point is not the software name; it is the quality of the input geometry, the accuracy of the photometric files and the designer’s interpretation of the result.

Beam angle is not enough

Two luminaires with the same nominal beam angle can produce very different centre-beam intensity, spill light and uniformity. For spotlight and projector work, review candela distribution and the full photometric curve together with mounting distance.

Mosque dome and ceiling calculations

For domes, false-colour analysis should consider the curved surface, drum, calligraphy band, pendentives, chandelier position and viewer sightlines. Narrow-beam projectors may highlight details while wider distributions create base illumination. Cove lighting and chandelier output should be calculated as separate layers before the final scene is combined.

Cultural and museum spaces

Exhibition lighting adds another variable: conservation limits. Illuminance and cumulative exposure should be chosen according to object sensitivity, curatorial policy and viewing requirements rather than using one universal value for every collection.

What to send for a project calculation

Send the latest plan and section, target areas, ceiling/dome heights, preferred fixture family if known, destination voltage, control requirements and any architectural restrictions. MosqueBuild can then prepare a fixture schedule, calculation report and coordinated lighting proposal.

Lighting calculation workflow

1. Import geometry: model the real room, dome, facade or exhibition space from current drawings.
2. Assign surfaces: enter realistic reflectance assumptions for ceilings, walls, floors and key materials.
3. Set calculation planes: floor, working plane, wall, artwork, dome surface or facade target as required.
4. Insert real luminaires: use manufacturer IES/LDT photometric data rather than generic light sources.
5. Aim and group: set orientation, beam direction, mounting height and control zones.
6. Calculate and review: inspect lux, uniformity, false-colour maps and glare-related outputs where applicable.
7. Iterate: change optics, quantity, position or power until the design target is met efficiently.
8. Document: issue calculation pages, luminaire schedules and aiming/placement information.

Inputs that materially change the result

How to read a lighting report

Do not judge a calculation from the average lux figure alone. Review the minimum and maximum values, uniformity, visual distribution, high-intensity hot spots, dark areas and the actual luminaire positions. For vertical architecture, check wall and facade planes instead of relying only on floor illuminance.

Key terms

• Lux: illuminance arriving on a surface.
• Candela: luminous intensity in a direction; especially important for long-throw projectors.
• Uniformity: relationship between lower and average/maximum illuminance depending on the metric used.
• False-colour map: visual map of calculated illuminance ranges.
• Isolux: contour lines connecting equal illuminance levels.
• UGR: one glare metric used in appropriate interior applications; applicability depends on the space and standard.
• IES/LDT: photometric data files describing a luminaire’s light distribution.

Calculation scenarios for mosque projects

A prayer hall can require several separate studies: floor-level ambient light, mihrab and qibla-wall emphasis, dome surface illumination, calligraphy accents, chandelier contribution and exterior night lighting. For a central dome, calculation points should follow the curved geometry rather than only a flat plane below it.

Calculation scenarios for museums and cultural spaces

Museum calculations should separate exhibit surfaces, circulation and ambient adaptation. Where conservation limits apply, the design team should also consider operating hours and cumulative exposure policy. A photometric model cannot replace conservation judgment; it provides measurable evidence for the chosen lighting strategy.

What a MosqueBuild lighting calculation package can contain

• calculation summary by zone
• false-colour lux maps
• luminaire quantity and model schedule
• beam angle / optic recommendation
• fixture coordinates and mounting heights
• aiming notes for adjustable luminaires
• connected load by scene or circuit group
• PDF report for technical review
• shop-drawing coordination notes when supply/manufacture is included

Часто задаваемые вопросы

Can fixture quantity be calculated from lumen output alone?

No. Geometry, optics, aiming, mounting height, surface reflectance and target performance all influence quantity.

Do DIALux and Relux produce the same result?

With equivalent geometry, assumptions and photometric data, the design conclusions should be broadly consistent. Differences often come from inputs, calculation settings or modelling choices rather than the software name itself.

What should I send for a calculation?

Send the latest plan and section, mounting heights, target areas, preferred luminaire family if known, voltage/control requirements and any project-specific performance criteria.