Graphics Programs Reference
In-Depth Information
When using a device like the Spectroscan, the user is asked to define
three corner patches so the instrument knows where all the other patches
lay on the target and can land on each patch correctly. One useful feature
of the Spectrolino is the ability to place a number of optional filters in
front of the sensor. There is a UV filter for those who have papers with
Optical Brighteners
. This can cause problems in the resulting profile
depending on the software package. Optical Brighteners are discussed in
more detail later in this chapter. An optional filter has a polarizer, which
is necessary when measuring certain materials. Although this ability to
replace filters isn't necessary for most users, for certain types of applica-
tions, this is a critical feature. The Spectroscan table has an optional light
source for measuring transparent media. This is known as the
Spectroscan
T X/Y table
. The robotic arm moves the Spectrolino over to this light
source and the user must measure a patch of transmissive material one
patch at a time. This is fine for occasional use, however, if a user needs
to build a profile from transmissive material like a Duratrans or a large
format transparency; there are better options (see next). This unit is ideal
for measuring color patches off a 4 ¥ 5 transparency for creating a custom
TDF for scanner profiles. Be sure to have plenty of time and a steady
hand to accomplish this task!
Automated Spectrophotometers, those that measure patches with
little or no human intervention, are ideal for users who have to either
build many profiles or measure targets daily for calibration purposes. The
Spectrolino/Spectrocam with X/Y table falls into this camp as does the
Eye-One Pro with Eye-One iO; however, since both units do not have to
be purchased with the automated table options, I placed them in the list
of handheld devices earlier.
There are a group of semi- and totally automated Spectrophotome-
ters. X-Rite makes a Spectrophotometer called the
DTP-41
as seen in Fig.
6-6. This unit is small and quite fast. All the user is required to do is place
the target into the unit, press a button, and then move the target over
one column and continue on with the next row. Although not totally
automated, the unit is fast at measuring a great deal of patches. The DTP-
41 averages 3 to 5 measurements per patch. The targets do need to be
printed to a very specific size in order to fit into the unit. The DTP-41
can be purchased with or without a UV filter but the filter cannot be
inserted or removed. In addition, there is a version called the
DTP-41T
,
which will measure transmissive materials as well as reflective materials.
For those that need to measure targets from transmissive originals like
backlit film or Duratrans, this is the unit to purchase. The
DTP-41
is very
fast and flexible, however, unlike handheld units discussed, it can only
be used to measure an item that can be inserted inside the unit.
GretagMacbeth has a Spectrophotometer named
iCColor
that is fully
automated, as seen in Fig. 6-7. A user places a target of fixed size and
width into either the top or front of the unit. The iCColor will move the
target and the sensor head in an X/Y position automatically. The user is
Definition
Optical Brighteners:
A
fluorescent compound
found in materials that
absorb invisible ultraviolet
light and reemit it as
visible light, producing a
brighter appearance from
that material (usually a
paper) than really exists.
