(Ill) 
:tails is required, 
the specification 
d 
siting Glare. 
graphically under 
ira will encounter 
used as tests of a 
ich is in effect an 
made in this case 
is necessary to 
series of planes 
ent laboratory 
exposures and 
mounting the 
this convenient 
n a single type of 
ig four types shall 
: on a dark back- 
d line lengths are 
ance between the 
low contrast test 
2.0 or greater. 
dark background, 
ne length is three 
0.20 ± 0.02. 
dimensions 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 far off axis in the usual collimator ar 
rangement, it is necessary to prepare elliptical test objects so that they 
are equivalent to circular test objects on a distant plane perpendicular 
to the camera axis. A sufficient variety of targets shall be prepared to 
ensure that the major and minor diameters on this virtual object plane 
do not differ from one another by more than 5%. 
note: Difference of log luminance has been specified for all test 
objects. This is numerically equal to difference in optical density 
only if the geometry of the illuminating and viewing system in 
the collimator is sufficiently similar to the geometry of the den 
sitometer used to obtain optical densities. 
1.3.6 Each target shall consist of a suitable range of sizes of one or 
more types of test object. Each size of object shall occur at least twice, 
orientations being chosen to provide at least radial and tangential lines, 
where applicable. Sizes shall be in geometric progression with 2 pre 
ferred for the common ratio. 
1.4 Illuminant. 
The illuminant shall be equivalent to the light source defined by 
the International Congress of Photography *) modified by whatever 
filter is usual on the camera. The filter used shall be specified fully in 
the report. Preferably its transmission curve should be given. 
note: Since 1928 there have been changes in the “candle” and 
the International Temperature Scale. The changes are small for 
photographic applications. This specification is not intended to 
revise the work of the International Congress of Photography; 
however, the following equivalents may be given for the conven 
ience of users: 
1928 1952 
At 2360 °K 1 old candle = 1.006 new candle or candela 
From 2600 °K 
to 3000 °K 1 old candle = 0.997 „ „ „ „ 
For equivalent ) (2360 °K = 2370 °K T ) 
spectral > <2660 °K = 2671 K ') 
distribution ) \2848 °K = 2860 °K x ) 
1) d. B. Judd, “The 1949 Scale of Color Temperature”, U.S. National 
Bureau of Standards, R.P. 2053, Jan. 1950. 
on a dark back 
er diameter. The 
i) See “The Unit of Photographic Intensity” Proceedings of the Seventh Inter 
national Congress of Photography, July, 1928, or American Standards Association 
Z 38.2.1, Section 3.3.2.4 or British Standards Institution B.S. 1380