Yes, emergency light covers can affect the brightness of the lights. The material, color, and design of the cover play significant roles in determining how much light is emitted and how it is distributed. 
1. **Material**: Covers made from opaque or thick materials can reduce the amount of light that passes through, thereby diminishing brightness. Transparent or translucent materials allow more light to pass, maintaining higher brightness levels.
2. **Color**: Colored covers can filter the light, altering its intensity and hue. For instance, a red or blue cover will absorb certain wavelengths, reducing overall brightness and changing the light's color.
3. **Design**: The design, including the shape and texture of the cover, can influence light diffusion. A cover with a frosted or textured surface can scatter light, reducing glare but also potentially decreasing perceived brightness. Conversely, a clear, smooth cover will allow more direct light transmission.
4. **Reflectivity**: Some covers are designed with reflective surfaces to enhance brightness by redirecting light. However, if the reflectivity is too high, it might cause glare, which can be uncomfortable or distracting.
5. **Size and Fit**: A cover that is too large or improperly fitted can block parts of the light source, reducing brightness. Properly sized and fitted covers ensure optimal light output.
In summary, while emergency light covers are essential for protection and aesthetic purposes, their characteristics can significantly impact the brightness and effectiveness of the emergency lighting system.