A1.2.1 Source Lamp— Consisting of a lamp of color temperature
of approximately 2750 K (or if a quartz halogen lamp
is used, approximately 2900 K). A source lamp providing a
translucent or opaque diffuse background of 900 6 100 lx
brightness against which the color standards and samples are
viewed has been found satisfactory to produce the necessary
spectral characteristics. The source lamp shall be designed so
that there is no extraneous light interfering with the observation