| Subject | English | German |
| opt. | threshold of visibility | Schwellenwahrnehmung (the threshold below which neither the cones nor the rods respond to a light stimulus) |
| opt. | threshold of visibility | Sichtbarkeitsgrenze (the threshold below which neither the cones nor the rods respond to a light stimulus) |
| opt. | threshold of visibility | Sichtbarkeitsschwelle (the threshold below which neither the cones nor the rods respond to a light stimulus) |
| opt. | threshold of visibility | Wahrnehmungsschwelle (the threshold below which neither the cones nor the rods respond to a light stimulus) |
| opt. | threshold of visibility | Unterschiedswahrnehmung (the threshold below which neither the cones nor the rods respond to a light stimulus) |
| tech. | threshold of visibility | Sichtbarkeitsschwelle |
| opt. | visibility threshold | Sichtbarkeitsgrenze |
| tech. | visibility threshold | Sichtbarkeitsschwelle |