Introduction
The lighting industry is filled with technical terms, specifications, and performance claims that if not properly understood, can lead to misinformed decisions. From Unified Glare Rating (UGR) issues to misleading efficiency claims, let’s clear up some of the biggest misconceptions in the industry.
1. UGR is Not a Fixed Property of a Fixture
A common misunderstanding is that UGR (Unified Glare Rating) is an intrinsic part of a luminaire’s design, like its weight, height, or length. This is not true. UGR is not a fixed characteristic of a fixture; it depends on the entire lighting environment, including room size, surface reflectance, and observer position. A luminaire cannot inherently have a UGR value—it can only contribute to one within a given setup. Unfortunately, many manufacturers advertise UGR as if it’s a static property, leading to misleading specifications and expectations.
2. The Misinterpretation of CCT, CRI, and Lumens
Another major misconception in the industry is the relationship between Correlated Colour Temperature (CCT), Colour Rendering Index (CRI), and Luminous Flux (lumens). Simply put, high lumens do not necessarily mean good lighting quality. If the CCT is too high and the CRI is low, the perceived quality of light can be poor, leading to unnatural and uncomfortable environments.
Manufacturers often push high-lumen outputs as a selling point without disclosing the impact of spectral quality. To make an informed decision, specifiers should consider CRI and CCT alongside lumen output rather than in isolation.
3. Stop Using 'Wattage' – It’s Power
Another frustrating misnomer in lighting discussions is the term “wattage.” The correct term is power, as wattage refers to a specific measurement (watts) of electrical consumption. When discussing the efficiency of a luminaire, it's crucial to focus on lumens per watt (lm/W) instead of just raw power consumption. Higher power usage does not automatically equate to better light output or efficiency. This is because luminous efficacy, measured in lumens per watt (lm/W), indicates how efficiently a light source converts energy into light, with higher (lm/W) values signifying greater efficiency and lower energy consumption. So in short, higher wattage does not mean better light output; (lm/W)does.
4. Luminous Efficacy vs Luminous Efficiency – So they aren’t the same thing?
Luminous Efficacy measures how efficiently a light source converts electrical power into visible light(lumens per watt), while Luminous Efficiency is the percentage of power converted into both visible and non-visible radiation. See points below:
Luminous Efficacy
· Represents the ratio of luminous flux (light output) to the electrical power consumed, measured in lumens per watt (lm/W).
· A higher luminous efficacy indicates that a light source produces more light for the same amount of energy consumed.
· It’s a key factor in assessing the energy efficiency of lighting devices.
· For example, a light source with a high luminous efficacy of 100 (lm/W) produces100 lumens of light for every watt of power consumed.
Luminous Efficiency
· Represents the percentage of electrical power converted into both visible and non-visible radiation.
· It’s a dimensionless quantity, meaning it doesn’t have units like lumens per watt.
· It's calculated by dividing the total luminous flux by the total radiant flux.
· A higher luminous efficiency indicates that alight source is more efficient at converting electrical power into light, regardless of whether that light is visible or not.
5. The Issues with Luminous Efficiency & Efficacy
A particularly deceptive practice in the industry is the inconsistent use of luminaire lumens per circuit watt, often leaving specifiers to calculate efficiency themselves. Some manufacturers omit crucial details like driver losses, resulting in misleading (lm/W) figures. If data sheets fail to account for these losses, the efficiency claims may be exaggerated.
Additionally,(lm/W) values should always be based on independent IES files tested at the required CCT and CRI. A low-CRI, high-Kelvin sample can be manipulated to show an artificially high (lm/W) value, but once produced at acceptable quality levels, the true (lm/W) figure is much lower. This discrepancy can lead to unrealistic expectations and incorrect product comparisons.
Incorrect lumen per watt values are a significant issue in the industry. Manufacturers may list idealised (lm/W) values rather than real-world figures under standard operating conditions. Always verify whether the stated (lm/W) figures come from independently tested data at the required CCT and CRI.
6. Energy Efficiency Claims Without Proper Comparison
Many manufacturers claim their products are “energy efficient” without specifying what they are being compared against. A luminaire can only be considered energy efficient if it maintains the same spatial, spectral, and temporal properties as the product it’s replacing. If these variables change, then the efficiency claim is meaningless. When evaluating energy efficiency, always check that comparisons are made against a relevant baseline.
7. Overlooked Reflectance Values and Maintenance Factors
Reflectance values and maintenance factors play a crucial role in long-term lighting performance. However, these are often left out of product discussions. A well-designed lighting solution should take into account how materials in the environment affect light distribution and how maintenance factors impact long-term efficiency.
8. Glare is not excessive brightness: It is a contrast ratio.
Glare has become a controversial talking point in the lighting industry. So, – what is it?
Glare is the contrast in a lighting environment that causes visual discomfort, reduces visibility, or impairs performance. It occurs when a light source is too intense relative to the surrounding luminance, making it difficult to see comfortably. Glare can be a major issue in mission-critical environments like cleanrooms, hospitals, semiconductor manufacturing, and industrial applications.
Different types of Glare:
Discomfort Glare - Causes irritation or fatigue but does not necessarily reduce visibility e.g. bright overhead lights in an office.
Disability Glare – Reduces visibility and impairs performance e.g. headlights shining into a driver's eyes at night.
Reflected Glare – Light bouncing off surfaces like screens or glossy desks creating unwanted reflections
Direct Glare – Light coming directly from an intense source, such as an uncovered LED fixture.
Why is glare so important?
· Workplace productivity – Excessive glare can lead to headaches, eye strain, and decreased focus.
· Safety– In mission-critical environments, like cleanrooms or industrial, glare can obscure important details, increasing the risk of accidents.
· Comfort and Well-Being – In office and healthcare settings, reducing glare improves employee satisfaction and visual comfort.
How to minimise glare when designing lighting?
As an OEM lighting manufacturer, we understand the importance of having low-glare LED fixtures. The list below will outline some of the key metrics for preventing glare.
1. Diffused Lighting – Use fixtures with diffusers or lens covers: These scatter light, reducing glare and creating a more comfortable visual environment.
2. Indirect Lighting – Indirect lighting such as up lighting or wall washing can reduce glare and create a more comfortable environment.
But glare is just excessive brightness I was told! Nope!
Many people mistakenly think glare is simply about lights being “too bright”. Glare is caused by high contrast ratios between a light source and its surrounding environments. See why below:
1. The Role of Contrast Ratio in Glare
· The human eye adapts to different light levels, but rapid changes between bright and dark areas create strain.
· Glare occurs when a small, extremely bright area is surrounded by a much darker field, forcing the eye to work harder to adjust.
· Example: A single bright LED downlight in a dim room causes discomfort, even if the total brightness isn’t excessive.
2. Why Brightness Alone Doesn’t Define Glare
· A well-distributed high-brightness environment (like a bright, uniformed office) may not cause glare.
· But a low-brightness environment with a single overly bright source (like a laptop screen in a dark room) can cause severe glare.
· It’s the intensity difference between areas that matters, not just the absolute brightness.
3. Key Factors that Cause Glare
· Unbalanced Luminance: A fixture is much brighter than the surrounding space.
· Poor Optical Control: Light is concentrated in one area instead of diffused evenly.
· Unshielded Light Sources: LEDs without diffusers or lenses.
· Reflections & Veiling Glare: Bright light reflecting off surfaces and reducing contrast.
4. How to Reduce Glare by Managing Contrast
· Diffuse Light Evenly – Micro prismatic diffusers, baffles, or indirect lighting enable uniform luminance across a larger area.
· Balance Light Levels – Avoid extreme differences in brightness across a room.
· Minimise Reflections – Position fixtures to avoid glare from screens or glossy surfaces.
Conclusion
Glare isn’t just about too much light – it's about the relationship between bright and dark areas. Managing contrast ratios effectively leads to comfortable, high-performance lighting without unnecessary eye strain.
What Should Be Done?
Rather than focusing on cherry-picked specifications that make a product look better on paper, manufacturers should provide a more transparent and holistic view of lighting performance. Below are some suggested solutions to improve industry transparency:
It is essential that lighting professionals have accurate data when making informed decisions, and these misconceptions should be highlighted, as such, leading the way to better practices and higher standards within the industry.
