Sekonic SR-3500 Operating Manual page 119

OMR glossary
Direct under type
If paper has pre-printed timing marks, the scanning area (reading area) of targeted
mark frames will be determined by such timing marks.
Direct under type refers to a method of reading a zone that is the same as the
timing mark width.
Other methods include timing control type, mark to mark type, and FACOM type.
Transmission interface
The hardware connecting a computer and the OMR, in other words the mediating
connection. The SR-3500,SR-6500 uses USB or RS-232C interfaces.
Dropout color
Refers to colors pre-printed or written on documents that people can see but that
don't appear when read with an image scanner or other devices.
There are "warm colors" and "cold colors" by appearance. Warm colors called
orange end, red end, etc. are used as OCR dropout colors, and you need to
switch fi lters in this device for bluish dropout color sheets such as the standard
forms used by the Japan Chain Stores Association. Bluish colored lines drop out
when they are scanned with copy machines and other devices even if they don't
use dropout color ink. OCR paper for fax machines uses "cold color (blue-green)"
dropout colors, but there are only a few colors that can be used with most fax
machines, because they are different from OCR units.
(1) Dropout color print darkness is controlled by the PCS value. There are two
ways to measure PCS, black backing and white backing, and you should
pay attention because they differ depending on the model.
(2) OCR sheets are generally used for printing character boxes using dropout
color inks and printing letters in clear areas.
(3) Recently, some models have become available that are capable of reading
black character boxes, but dropout color printing sheets are often superior
in both recognition performance and processing speed.
(4) Dropout colors are chosen by spectral characteristics and PCS values
that are determined by scanner sensor, light source, and fi lter.
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Timing mark
Mark frame
Reading area