target/spotread
Summary
Use an instrument to read a single color value. This can be a useful
diagnostic aid.
Usage Summary
spotread [-options]
-v
Verbose mode
-d
Print debug diagnostics
-s
Print spectrum for each reading.
-S
Plot
the spectrum in a graph window.
-c comport
Set COM port, 1..4
(default 1)
-i 41|51|92|94SO|SS Select target
instrument
-t
Use
transmission measurement mode
-e
Use emissive measurement mode (absolute results)
-y c|l
Display type, c = CRT, l = LCD
-l illum
Choose
illuminant for print/transparency spectral data:
A, D50 (def.), D65,
F5, F8,
F10 or file.sp
-o observ
Choose CIE
Observer for
spectral data:
1931_2, 1964_10, S&B
1955_2, J&V 1978_2 (def.)
-N
Disable auto calibration of instrument
(Choose FWA during
operation)
Usage Details and Discussion
spotread operates in a similar fashion to printread, but allows the reading of a
succession
of single color values. This can be useful in diagnosing issues with
profile
creation
and operation.
The -v flag causes extra information to be
printed out during
printread operation.
The -d flag causes serial communications
diagnostics to be printed to stdout. This can be useful in tracking
down why an instrument can't connect.
The -s flag enables the printing out spectral
reflectance/transmittance values, if the instrument supports this.
The -S flag enables the plotting of the
spectral
reflectance/transmittance values, if the instrument supports this. If a
reference is taken, this will be plotted in red. You must strike a key
in the plot window to continue with another measurement.
The instrument is assumed to communicate through a
USB or serial communication port, and the port can be selected with the
-c
option,
if the instrument is not connected to the first port. If you invoke dispread
so as to display the usage
information (i.e. "dispread -?" or "dispread --"), then the discovered
USB and serial ports will be listed. On
UNIX/Linux, a list of all possible serial ports are shown, but not all
of them may
actually be present on your system.
By default spotread will either determine the
type of instrument if a USB port is selected, or for serial ports, one
must be selected using the -i
parameter. 41 selects the
X-Rite DTP41, 51 selects the
X-Rite DTP51, 92 selects the
X-Rite DTP92, 94 selects the
X-Rite DTP94, SO or SS selects the Gretag
Spectrolino, SpectroScan or SpectroScanT. All instruments will be used
in a spot mode. For the SpectroScan instrument, the samples can be
placed on the table, and the measuring head positioned before taking a
measurement. Note that the default mode (reflectance measurement) may
not be supported by the instrument, so a mode it does support should be
selected using the command line options. Note that the DTP51, DTP92 and
DTP94 are colorimeters, and cannot read
spectral information, and that the DTP92 can only read CRT type
displays.
If using an Xrite DTP41T or SpectroScanT, and printing
onto transparent or back lit
media, use the -t flag to operate the instrument in
transparency mode. If using the Spectroscan, this triggers a fake
transparency
mode, that uses a separate backlight (such as a light box). The
instrument will be used to calibrate the level of backlight, and use
this to compute the transparency of the test chart samples. Note that
for good transparency values, the backlight level needs to be neither
too bright not too dark, should ideally be incandescent rather than
fluorescent (since fluorescent lights often have big dips in their
spectrum), and ideally should be of uniform brightness over the
measurement area.
The -e flag
allows measuring
in emission mode (e.g. displays or illuminants) using instruments that
support this mode. Values returned are absolute.
Display type. Some colorimeters (like the DTP94)
can
do a more accurate jib if they know what type of display technology is
used. Use -yc if you are
calibrating a CRT (Cathode Ray Tube) type monitor, and use -il if you are calibrating an LCD
(Liquid Crystal Display).
The -l flag allows specifying a standard or
custom illumination
spectrum, applied to reflective spectral data to compute CIE
tristimulus values. A, D50, D65, F5, F8,
F10 are a selection of standard illuminant spectrums, with D50
being the default. If a filename is specified instead, it will be
assumed to be an Argyll
specific .sp spectrum file.
The -o flag allows specifying a tristimulus
observer from a
built in set.
1931_2 selects the standard CIE 1931 2 degree observer.
1964_10 selects the standard CIE 1964 10 degree observer.
1955_2 selects the Stiles and Birch 1955 2 degree
observer
1978_2 selects the Judd and Voss 1978 2 degree observer
shaw selects the Shaw and Fairchild 1997 2 degree
observer
The -N flag disables any automatic instrument
calibration (used for the Gretag Spectrolino for instance). This would
be used when the instrument is being used for a series of measurements,
and it is inconvenient to place it on it's calibration tile between
measurements. The instrument should be calibrated at least once for
each measurement session though.
Once spotread has established communications with the
instrument, it awaits a command from the user, indicated by the user
hitting a key.
If Fluorescent Whiter Additive (FWA) compensated readings are to be
made, then this needs to be enabled and setup by first reading the
paper white background
color to establish an FWA reference. There are 25 FWA reference
locations
available, keyed to the keys A-Q and S-Z (must be
capital letters).
Once a particular reference location is initialized with the FWA paper
color, subsequent readings will use FWA compensation for that keyed
location.
If FWA readings are not to be performed, then a reading for a location
that has not been initialized should be used.
Spot readings are performed by hitting a key a-q or s-z
(must be lower case letters).
The previous reading can be stored as a reference, and delta E's
computed for each reading, using the r key.