TE270X 
OECF Chart ( following ISO14524/15739)

The TE270X chart is similar to the TE264
but it is equipped with two polarizing filters
in the center of the chart. For cameras that
do not allow a manual adjustment of the
exposure, the automatic exposure control
(AEC) is fooled by modifying the density
(transmission) of the central part of the
test chart. This feature is needed especially
for low-end cameras and camera modules
in devices that often do not have a
manual exposure adjustment.