1951 USAF Resolution Target Data

Group

Element

Frequency

Line Width (um)

Group

Element

Frequency

Line Width (um)
 

-2

1

0.2500

2000

  

4

1

16.00

31.3
  2 0.2806 1782     2 17.96 27.8
  3 0.3150 1587     3 20.16 24.8
  4 0.3536 1414     4 22.63 22.1
  5 0.3969 1260     5 25.40 19.7
  6 0.4454 1122     6 28.51 .17.5
 
-1 1 0.5000 1000   5 1 32.00 15.6
  2 0.5612 891     2 35.92 13.9
  3 0.6300 794     3 40.32 12.4
  4 0.7071 707     4 45.25 11.0
  5 0.7937 630     5 50.80 9.84
  6 0.8909 561     6 57.02 8.77
 
0 1 1.000 500   6 1 64.00 7.81
  2 1.122 445     2 71.84 6.96
  3 1.260 397     3 80.63 6.20
  4 1.414 354     4 90.51 5.52
  5 1.587 315     5 101.6 4.92
  6 1.782 281     6 114.0 4.38
 
1 1 2.000 250   7 1 128.0 3.91
  2 2.245 223     2 143.7 3.48
  3 2.520 198     3 161.3 3.10
  4 2.828 177     4 181.0 2.76
  5 3.174 157     5 203.2 2.46
  6 3.564 140     6 228.1 2.19
 
2 1 4.000 125   8 1 256.0 1.95
  2 4.490 111     2 287.4 1.74
  3 5.040 99.2     3 322.5 1.55
  4 5.657 88.4     4 362.0 1.38
  5 6.350 78.7     5 406.4 1.23
  6 7.127 70.2     6 456.1 1.10
 
3 1 8.000 62.5   9 1 512.0 0.977
  2 8.980 55.7     2 574.7 0.870
  3 10.08 49.6     3 645.1 0.775
  4 11.31 44.2     4 724.1 0.691
  5 12.70 39.4     5 812.7 0.615
  6 14.25 35.1     6 912.3 0.548



The USAF 1951 resolution target was created due to the need to assign numerical tolerances to optical systems and photographic processes. The resolution range depends on the quality and functioni of the system or process being tested. In the standard Air Force 1951 target, the change in pattern size is in a geometric progression based on the sixth root of 2. To simplify, the number of lines per millimeter doubles with every sixth target element. These six elements are known as a group, and the group heading, such as -2, is the power of 2 to which the first element is raised to express the number of lines per millimeter in that element. In other words, 2 to the -2 power (2^-2) is 0.25 line per millimeter, 2 to the 0 power (2^0) is one line per millimeter, and so forth.

The following table dipicts the MIL-STD-150A standard, representing the scaling factors.

Element of Group

 Factor (mathematical)

Factor (numerical)

1

20

1.00000

2

2-1/6

0.89090

3
2-2/6=

0.79370

4
2-3/6 =

0.70711

5

2-4/6

0.62996

6

2-5/6

0.56123