Upon reading an A3-size sample image, a colorimeter that can read A3 size can
be used but such A3-size calorimeter is expensive. For this reason, an A3-size
recording paper sheet is cut into halves, i.e., two A4-size sample images, which
are measured by an A4-size calorimeter. To prevent such troublesome operation,
color patches are divided into nearly half groups, and these color patch groups
are printed on an A3-size recording paper sheet to have their top positions on
the opposite sides. In this way, after one color patch group is measured, the sample
image is rotated through 180 and is set on the calorimeter to measure the
other color patch group.
