GUIDANCE FROM THE COLLEGE OF OPTOMETRISTS
Lenses for protection against sun glare fall into five groups, according to their range of luminous transmittance.
Lenses with a luminous transmittance of less than 75% are not suitable for road use in twilight or at night. Transitions DriveWear lenses in their rested (inactivated, low light) state have a transmission value of 65% and therefore are unsuitable for twilight or night driving.
| Filter category | Description | Range of luminous transmittance in the visible spectral range |
| 0 | clear or very light tint | from over 80% to 100% |
| 1 | light tint | from over 43% to 80% |
| 2 | medium tint | from over 18% to 43% |
| 3 | dark tint | from over 8% to 18% |
| 4 | very dark tint | from over 3% to 8% |
