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You Are Here : Home >> Products >> Image test chart >> Grey Scale Card >> LOGARITHMIC GRAY SCALE TEST CHART

LOGARITHMIC GRAY SCALE TEST CHART

Two 9-graduated counter current gray scales are arranged on a gray background (D = 0.75), the gray scales being graduated logarithmically (gamma = 0.45).
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Date:2017-07-07  Browse:
  • Introduction
  • Product Software

LOGARITHMIC GRAY SCALE TEST CHART

REFLECTANCE

Two 9-graduated counter current gray scales are arranged on a gray background (D = 0.75), the

gray scales being graduated logarithmically (gamma = 0.45). The output signal of an optimal

gamma-corrected camera yields two 11-graduates counter current linear step signals. The contrast

range of the gray scales is 50 : 1.


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

 

Step

Density

Reflectance in %

Output voltage in %

1

0.15

71

100

2

0.26

55

88.75

3

0.37

42

77.5

4

0.51

31

66.25

5

0.67

22

55

6

0.85

14

43.75

7

1.09

8

32.5

8

1.40

4

21.25

9

1.85

1

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The density value are based on a density of BaSO4 = 0. Two fields of black velvet and white are

located between the gray scales. The density of the black field is D > 2.4 (reflectance > 0.5%). The

density of the white field is 0.09 (reflectance = 79%).

When the second brightest gray step (D=0.26) is adjusted to a 100% signal level, the gray scale

has the High Dynamic Range of 1:40 which is recommended for TV productions. The brightest step

then shows the effect of the knee function. In order to see a finer graduation of the knee function

and to observe its effects in the 3 channels we recommend an overexposure of 2 steps. The white

area in the center can also be used for adjusting the white level limiter. No generally valid statements

can, however, be made on the height of the level limit (e.g. 105%), since this varies according to the

respective use (Betacam e.g. 101%).