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3« The measurements shall be made on axis and at 15° 
each side of axis, in the horizontal. 
4. The scanning direction shall be both radial and 
tangential. 
5« The measurements shall be performed in a narrow 
spectral region centered on 546 nm, transmission 
of the filter to be indicated. If possible, meas 
urements shall also be made using a broader spectral 
region approximately fitting the spectral response 
of an ’'extended-red 1 ' panchromatic emulsion including 
a Wratten 21 filter, (e.g. Eastman Kodak emulsions 
such as Plus X Aerographic, which have approximately 
uniform sensitivity from 500 to 700 nm)• A sheet of 
Wratten 21 filter is enclosed with the lens. A curve 
showing the actual spectral sensitivity used shall be 
provided with the test results. 
6. The measurements shall be made in planes 0.1 mm apart, 
referenced to the plane giving a maximum value for the 
transfer function at 40 lines/mm on axis. 
7. The measurements shall be made at spatial frequencies 
up to the limit which is convenient with the apparatus, 
preferably to 300 lines per mm on axis. 
8. An estimate of the accuracy of the measurements and a 
discussion of the relevant factors would be of value.