The Disability Glare Factor (DGF) is a measure of the amount of bothersome glare a light source creates , which impairs visibility of objects. This type of glare occurs when too much stray light or reflections enter the eye , leading to reduced contrast and visual performance .
1. Characteristics of the Disability Glare Factor (DGF)
✅ Measures the level of glare that affects visibility.
✅ Used in lighting design and ergonomics to optimize visibility.
✅ High DGF = more glare and poorer visibility.
✅ Depending on the light source, light intensity and environment .
✅ Important in architecture, street lighting, car lighting and screens .
2. How does disability glare arise?
📌 Too bright light sources → Direct sunlight, car headlights, street lights.
📌 Light reflections on smooth surfaces → Glass, water, metal or wet roads.
📌 Insufficient contrast between object and background → Strong light sources disrupt contrast.
📌 Light distribution in the eye → For example, in case of eye abnormalities such as cataracts.
3. How is the DGF affected?
| Factor | Effect on DGF |
|---|---|
| Light intensity (candela/m²) | The higher the intensity, the more glare. |
| Contrast with background | Lower contrast increases the annoying glare. |
| Light sources in the field of view | Directly visible bright lights increase DGF. |
| Eye health and age | Older eyes are more sensitive to glare. |
📌 Especially in road safety and workplaces, it is important to keep DGF low.
4. Applications of DGF in lighting and design
| Application | Measures against high DGF |
|---|---|
| Street lighting | Use of shielded lamps and lower light intensity. |
| Car lighting | Anti-glare headlights and low beam systems. |
| Workplaces and offices | Anti-reflective screens and correct positioning of light sources. |
| Screens and monitors | Matte screen coatings and lower brightness settings. |
| Architecture | Use of indirect lighting and sun blinds. |
📌 A good lighting strategy helps to minimize DGF and improve visual comfort.
5. Difference between Disability Glare and Discomfort Glare
| Type of Glare | Effect | Example |
|---|---|---|
| Disability Glare | Affects vision and reduces contrast | Glare from headlights on a wet road. |
| Discomfort Glare | Eye irritation without loss of vision | Too bright fluorescent lights in an office. |
📌 Disability Glare obstructs vision, while Discomfort Glare is mainly a nuisance without causing immediate vision loss.
💡 In short:
The Disability Glare Factor (DGF) measures the amount of bothersome glare a light source causes , leading to poor visibility and reduced contrast perception . It is influenced by light intensity, reflections, and environmental factors and is crucial in road safety, workplaces, and architecture to reduce glare.