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out under the supervision of scientists experienced in the field of optical and photographic 
measurements. Hence, it does not specify the quality of the equipment. which shall be used 
nor the procedural details necessary to obtain correct results. A few explanatory and 
warning notes are included in the recommendation where the philosophy or procedure may 
be unfamiliar in some countries. If any further information on certain details is required, 
please enquire of the Secretary, Commission I. 
Calibration is useful only if data can be linked reliably to photography. Cameras, 
magazines, and filters shall be of such construction and condition as to ensure maintenance 
of the calibration under normal use. It is important that reports carry complete identific- 
ation information including the following items where applicable: optical unit (cone) 
number (use camera number if no separate optical unit), lens number, filter number, 
register glass number, magazine number, vacuum back number, pressure pad number, 
camera port glass number, date of test, testing laboratory. Each page of the report should 
carry the report number, or the number of the item tested and the test date. 
1. RESOLVING POWER 
1.1 Resolving power shall be determined photographically under conditions ap- 
proaching closely those which the camera will encounter in service. 
1.2 The camera tests described below may also be used as tests of a lens alone 
by mounting the lens on a test bench which is in effect an adjustable camera. 
Major changes of procedure to be made in this case are indicated. 
  
NOTE: For characterization tests of lens types it is necessary to make 
photographie resolving power tests in a series of planes representing a 
range of focus settings. Convenient laboratory methods for obtaining the 
necessary number of exposures and the necessary focus adjustments usually 
involve mounting the lens on a test bench or test camera. 
  
  
  
1.3 Target 
1.3.1 It is not possible at present to standardize on a single type of resolving 
power target. One or more of the following four types shall be used. 
1.3.2 Three Line Low Contrast 
This test object consists of three bright lines on a dark background. Line 
separations are equal to line widths and line lengths are five times line widths. 
The difference of log luminance between the lines and the background is 0.20 
0.02. 
1.3.3 Three Line High Contrast 
This test object is the same as the three line low contrast test object except 
+ 
that the difference of log luminance is 2.0 or greater. 
1.3.4 Cobb Low Contrast 
This test object consists of two bright lines on a dark background. The line 
separation is equal to the line width. Line length is three times line width. The 
difference of log luminance is 0.20 — 0.02. 
1.3.5 Annulus Low Contrast 
This test object consists of a bright annulus on a dark background. The outer 
diameter is three times the inner diameter. The dimension defining the size of an 
annulus is the mean of the inner and outer diameters. The difference of log 
luminance is 0.20 = 0.02. When annulus targets are used for off-axis in the