Patent ID: 7274386

Claim:
A method for determining a visual range, comprising: in order to produce measured contrast values, measuring a contrast at an object from at least two measuring positions of a measuring device situated at different distances from the object; and converting a change in the measured contrast values to the visual range; wherein the visual range is determined according to the following relationship: δ = x 2 - x 1 ln ⁡ ( c ⁡ ( x 1 ) / c ⁡ ( x 2 ) ) = x 2 - x 1 ln ⁡ ( c ⁡ ( x 1 ) ) - ln ⁡ ( c ⁡ ( x 2 ) ) wherein δ denotes the visual range, x 1 and x 2 are distances of the at least two measuring positions from the object, and c denotes contrast.