The Discomfort Glare Factor (DGF) is a measure of how bothersome a light source is perceived to be , without necessarily leading to reduced vision or loss of contrast. This type of glare causes eye strain, irritation, and impaired concentration , but not necessarily poor vision as with Disability Glare .
1. Characteristics of the Discomfort Glare Factor (DGF)
✅ Measures the degree of visual discomfort caused by bright light .
✅ Increased DGF leads to fatigue, headaches and loss of concentration .
✅ Depending on light intensity, viewing direction and environment .
✅ Important in lighting design for offices, homes and public spaces .
✅ Varies per person → Older people and people with sensitive eyes experience discomfort more quickly.
2. Factors That Influence Discomfort Glare
| Factor | Effect on DGF |
|---|---|
| Light intensity (lux) | The brighter the light, the higher the DGF. |
| Contrast between light sources and surroundings | Stark contrasts increase discomfort. |
| Viewing direction towards light source | Direct exposure increases DGF. |
| Color temperature | Cool white (5000K-6500K) light is perceived as sharper than warm white light. |
| Flashing or flickering lights | Fluctuating light sources increase fatigue and discomfort. |
📌 DGF plays a major role in work environments, where poorly designed lighting can reduce productivity.
3. Difference between Discomfort Glare and Disability Glare
| Type of Glare | Effect | Example |
|---|---|---|
| Discomfort Glare (DGF) | Annoying light, but visibility is maintained | Bright fluorescent light above a desk causes eye strain. |
| Disability Glare (DGF) | Glare that reduces visibility | Headlights of an oncoming vehicle reduce visibility in the dark. |
📌 Discomfort Glare irritates, while Disability Glare actively worsens your vision.
4. How can DGF be reduced?
🔹 Use of indirect lighting → Avoid direct exposure to bright light sources.
🔹 Placing diffusers and reflectors → Distributes light more evenly in a room.
🔹 Optimize color temperature → Warm tones (2700K-4000K) reduce discomfort.
🔹 Dimmable lighting → Ability to adjust light intensity to suit your needs.
🔹 Anti-reflective screens and matte surfaces → Prevent annoying reflections in workplaces.
📌 A good lighting design with balanced brightness and color temperature helps to minimize DGF.
5. Applications of DGF in lighting design
🏢 Offices → Poor lighting leads to reduced concentration and increased fatigue.
🏠 Living Spaces → Bright, direct lighting can be uncomfortable for relaxation.
🚗 Car lights → Dashboard lights and street lamps can cause discomfort.
🎭 Theaters and cinemas → Incorrect lighting can disrupt the experience.
📌 DGF optimization is crucial in environments where comfort and productivity are important.
💡 In short:
The Discomfort Glare Factor (DGF) measures how bothersome a light source is perceived to be without causing immediate vision loss. A high DGF leads to irritation, fatigue, and difficulty concentrating , but can be mitigated by indirect lighting, diffusers, and adjusted light intensity .