UNDERSTANDING LUX AND LUMENS: A TECHNICAL GUIDE FOR ARCHITECTS & SPECIFIERS

How light quantity, quality, and distribution shape architecture, wellbeing, and material performance.

Lighting is one of the most powerful spatial tools available to architects and specifiers. Whether illuminating a retail façade, shaping ambience through fabric lightboxes, or ensuring visual comfort in a healthcare environment, understanding the fundamentals of lumens and lux is essential. These two terms are often used interchangeably, but they serve very different purposes — and mastering them leads to more accurate specifications, better design outcomes, and fewer onsite surprises.

This guide breaks down lux and lumens from an architectural perspective, linking the science of light to the practical realities of materials, installation, ergonomics, and human-centred design.

WHAT ARE LUMENS?

Lumens = Total Light Output

Lumens (lm) measure the total quantity of visible light emitted by a light source. Think of lumens as the “power” or “capacity” of a luminaire — how much light it is capable of producing regardless of where the light goes.

Key points for architects:

• Lumens describe the raw light output of LEDs, strips, and modules.
• More lumens ≠ better lighting unless the light is controlled, diffused, and used effectively.
• Lumens help compare products during specification — e.g., choosing between LED modules for lightboxes or ceiling systems.
• Lumens never describe the actual brightness of a surface, space, or task plane.

Analogy:
Lumens are like the litres per minute produced by a tap — but that doesn’t tell you how much water lands where you need it.

WHAT IS LUX?

Lux = Light on a Surface

Lux (lx) measures how much light actually arrives on a given surface — walls, tasks, artwork, fabric tension systems, signage, or architectural finishes.

1 lux = 1 lumen per square metre

Lux is where the lived experience happens. It tells you:

• How bright a reception desk will feel
• How evenly a fabric lightbox is illuminated
• Whether a corridor meets compliance
• How comfortable a workspace or healthcare environment will be
• Whether brand graphics, textures, and colours actually “read” as intended

Lux is the real-world result of how lumens are distributed.

THE RELATIONSHIP BETWEEN LUMENS AND LUX

Distribution + Distance + Diffusion = Lux

You can transform lumens into lux through:

• Distance: Light intensity drops dramatically with distance (inverse square law).
• Beam angle: Narrow beams concentrate lumens into a smaller area → higher lux.
• Diffusers & fabrics: Materials spread, soften, and redistribute light → lower peak lux but more uniformity.
• Reflectance: Walls, ceilings, and floors absorb or bounce light.

Example:
A 6000-lumen LED module placed behind a large 2m × 1m fabric panel may only deliver ~200–350 lux on the surface after diffusion.
Same module in a 200mm × 200mm area may exceed 1200 lux.

Architectural takeaway:
Lighting output is only meaningful when matched to scale, materiality, and distance.

WHY ARCHITECTS & SPECIFIERS MUST DIFFERENTIATE LUX AND LUMENS

a) Ensuring Visual Comfort

Spaces that are “high lumen but low lux” often feel flat or under-lit.
Spaces with “high lux but harsh distribution” feel glary and uncomfortable.

Understanding the difference helps:

• Reduce glare
• Avoid over-lighting
• Improve task visibility
• Support circadian-aligned design

b) Accurate Fabric Lightbox & Tension System Specifications

Lightboxes, stretched ceilings, and fabric systems rely heavily on diffusion and distance from LED to surface.

Without lux data, you risk:

• Hot spots
• Banding
• Uneven illumination
• Dark edges
• Colour shifts

Architects specifying SEG systems should always request:

• Recommended lux range on the fabric surface
• LED pitch
• Diffusion distance
• Beam angle
• CRI and CCT data

c) Compliance & Standards

Most standards reference lux, not lumens.
Common guidelines include:

Space Type	Recommended Lux
Office task areas	320–500 lux
Retail circulation	300–500 lux
Retail feature walls / hero zones	800–1500 lux
Healthcare patient rooms	100–300 lux
Healthcare procedure areas	500–1000 lux
Aged care living spaces	150–300 lux
Hospitality dining	100–300 lux
Art display	50–300 lux depending on conservation requirements

d) Human-Centred Design

Even distribution of lux:

• reduces cognitive load
• improves visual perception
• supports orientation and safety
• enhances emotional response

This is especially relevant in:

• healthcare
• aged care
• educational design
• retail
• transportation hubs

HOW FABRIC SYSTEMS TRANSFORM LUMENS INTO USABLE LUX

Fabric plays a critical role in light behaviour. In systems like:

• Lucent™ illuminated frames
• Lunar™ stretched ceilings
• Resonate™ acoustic systems with integrated lighting
• Custom architectural light surfaces

…architectural fabric becomes the final luminous plane.

Fabric impacts lux through:

• Opacity & diffusion (light transmission %)
• Texture (smooth vs. open weave)
• Colour (white = maximum lux; colours absorb photons)
• Print density (graphics reduce lux by 5–30%)

Material selection must be matched with:

• lumen output of LEDs
• module spacing
• the depth of the system (80mm, 100mm, 120mm, etc.)

Architectural best practice: always assess lux on the surface, not lumens on the LED board.

LUX LEVELS FOR DIFFERENT ARCHITECTURAL APPLICATIONS

a) Backlit Graphics & Fabric Lightboxes

Typical target: 800–1200 lux on the face for premium retail.
Lower for ambient signage: 300–600 lux.

b) Stretched Ceilings

Diffuse ceiling luminaires often aim for 200–500 lux across a broad plane.
This supports uniform, shadow-free lighting.

c) Acoustic Panels with Integrated Lighting

Where acoustic + lighting merge:

• 150–300 lux is usually optimal
• It balances mood, orientation, and visual comfort

High acoustic absorption often means thicker substrates → careful planning prevents significant lux loss.

HOW TO CALCULATE LUX FROM LUMENS (SIMPLE METHOD)

A simplified formula:

Lux = Lumens ÷ Area

But this is only a starting point because real conditions are introduced:

• beam angle
• reflectance
• diffusion loss
• distance from source
• optical efficiency

For precision, architects typically use:

• DIALux
• AGi32
• Revit / BIM lighting plug-ins
• Manufacturer photometric data (IES files)

COMMON SPECIFICATION MISTAKES TO AVOID

Mistake 1: Specifying by lumens only - leads to uneven or under-performing installations.

Mistake 2: Not accounting for diffusion loss - Fabric, acrylic, and textured finishes can reduce lux 20–40%.

Mistake 3: Ignoring distance - Double the distance = one-quarter of the lux.

Mistake 4: Over-lighting printed graphics - High lux can wash out colours. Balance is key.

Mistake 5: Assuming all LEDs are equal - CRI, spectrum, binning, and optical efficiency dramatically change perceived brightness.

BEST-PRACTICE GUIDELINES FOR ARCHITECTS & SPECIFIERS

• Always specify lux on the target surface, not lumens from the LED.
• Request IES files for accurate modelling.
• Match fabric type to the expected lux level.
• Consider circadian lighting and the emotional experience.
• Design for uniformity, not just brightness.
• Understand that profile depth and LED pitch directly determine lux uniformity.
• For printed graphics, confirm lux tolerance to avoid colour degradation.

CONCLUSION

Understanding the relationship between lumens and lux empowers architects and specifiers to create lighting solutions that are technically accurate, human-centred, and visually compelling. Whether illuminating a hero wall, designing a stretched ceiling, or integrating lighting into acoustic or fabric tension systems, the right lux levels ensure that spaces perform the way they were intended — visually, functionally, and emotionally.