LOGARITHMIC GRAY SCALE TEST CHART

REFLECTANCE

Two 11-graduated counter current gray scales are arranged on a gray background (D=0.75),

the gray scale being graduated logarithmically.

Related to the densities of the gray scales: gamma = 0.45

Related to the reflectance values (brightness): gamma = 2.2 , that being exactly the reciprocal

value of gamma = 0.45.

The output signal of an optimally gamma-corrected camera yield two 11-graduates counter

current linear step signals. The contrast range of the gray scales is 40 : 1.

The values of the 11-graduated gray scale are as follows:

The density values are based on BaSo₄ = 0. Two black fields and a white field are

located between the gray scales, the density of the black filed is D > 2.4 (reflectance

< 0.5 %). The density of the white filed is D = 0.05 (reflectance = 89.9 %).