target/spotread
Summary
Use an instrument to read a single color value. This can be a useful
diagnostic aid. The type of instrument is determined by the
communication port
selected.
Usage Summary
spotread [-options]
[logfile]
-v
Verbose mode
-s
Print spectrum for each reading.
-S
Plot
the spectrum in a graph window.
-c comport
Set COM port, 1..4
(default 1)
-t
Use
transmission measurement mode
-d
Use display measurement mode (absolute results)
-db
Use display white brightness relative measurement mode
-dw
Use display white relative measurement mode
-e
Use emissive measurement mode (absolute results)
-a
Use ambient measurement mode (absolute results)
-y
c|l
Display type, c = CRT, l = LCD
-i 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
(def.),
1964_10, S&B
1955_2, shaw, J&V 1978_2
(Choose FWA during
operation)
-N
Disable auto calibration of instrument
-f filter
Set filter configuration:
n
None
p
Polarising filter
6
D65
u
U.V. Cut
-F extrafilterfile Apply extra
filter compensation file
-x
Display Yxy instead of Lab
-T
Display correlated color temperatures and CRI
-N
Disable auto calibration of instrument
-H
Use high resolution spectrum mode (if
available)
-W n|h|x
Ovride serial port flow control: n = none, h = HW, x = Xon/Xoff
-D [level]
Print
debug diagnostics to stderr
logfile
Optional file to save reading results
Usage Details and Discussion
spotread operates in a similar fashion to chartread, 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
chartread operation.
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.
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 -d flag
allows measuring
in display mode, using
instruments that
support this mode. Values returned are absolute.
The -db flag
allows measuring
in display mode using
instruments that
support this mode, with the brightness normalized to the white value
read as the first reading. While the brightness values are then
relative to the white, the readings are otherwise absolute. This
corresponds to the raw ICC absolute readings created by dispread.
The -dw flag
allows measuring
in display mode using
instruments that
support this mode, with the white normalized to the white value
read as the first reading.
The -e flag
allows measuring
in emission mode (e.g. displays or illuminants) using instruments that
support this mode. Values returned are absolute.
The -a flag
allows measuring
in ambient illumination mode using instruments that
support this mode (i.e. Eye-One Display 2). Values returned are
absolute, and include the various color temperatures and Color
Rendering Index (see -T). If
the instrument does not
support ambient mode, emissive mode will be used instead.
Display type. Some colorimeters (like the DTP94
and Eye-One Display)
require that the the type of display technology used be specified. 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 -i 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, and is used to compute PCS (Profile Connection Space)
tristimulus values. The following choices are available:
1931_2 selects the standard CIE 1931 2 degree observer.
The default.
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.
The -f options allows configuring the
instrument to have a particular filter fitted to it. Some instruments
(i.e. the Gretag Spectrolino) allow the fitting of various filters,
such as a polarizing filter, D65 illuminant simulation, or Ultra Violet
Cut filter, and this option allows the instrument to be configured
appropriately.
The -F option allows the setting of an extra
filter compensation file, that allows for the filtration of the
spectral readings through a medium of some kind, when in emission mode.
This is useful in allowing for such things as telescopic adapters that
use a glass of acrylic lens in the optical path.
The -x option causes the reading to be
displayed as XYZ and Yxy values, rather than the default XYZ and L*a*b*
The -T option causes various color temperatures
to be displayed, plus the Color Rendering Index. Three color
temperatures will be shown. The first is
the classic Correlated Color Temperature, which is the black body
(Plankian) color closest to the measured color in the CIE 1960 UCS
color space. The second is the black body (Plankian) color that has a
minimum CIEDE2000 error to the measured color. The last is the daylight
color that has a minimum CIEDE2000 error to the measured color. The
delta E between the closest temperature and the measured color is also
shown for each. The Color Rendering Index (CRI Ra) is also computed if
the instrument is capable of spectral measurement. If the notation (Invalid) is displayed after the
CRI, then this means that the the spectrum white point is to far from
the black body and Daylight locus to be meaningful.
The -N option disables the automatic
calibration
of an instrument if it is possible to do so. Sometimes it is awkward to
have to re-calibrate and instrument every time a utility starts, and
unnecessary if the instrument has recently been calibration, and this
switch prevents it happening.
The -H option
turns on high resolution spectral mode, if the instrument supports it.
See Operation of particular instruments
for more details.
The -W n|h|x
parameter overrides the default serial communications
flow control setting. The value n
turns all flow control off, h
sets hardware handshaking, and x
sets Xon/Xoff handshaking. This commend may be useful in workaround
serial communications issues with some systems and cables.
The -D flag causes communications
and other instrument diagnostics to be printed to stdout. A level can
be set between 1 .. 9, that may give progressively more verbose
information, depending on the instrument. This can be useful in
tracking
down why an instrument can't connect.
The logfile is an
optional file that can be specified to capture each reading taken.
There will be column headers printed to the first row, and then each
reading will be on a separate line with tab separators.
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 will be
selected automatically. Override this on the command line if desired.
Note that the DTP51, DTP92, DTP94 and Eye-One Display are colorimeters,
and cannot read
spectral information, and that the DTP92 can only read CRT type
displays.
Once spotread has established communications with the
instrument, it awaits a command from the user, indicated by the user
hitting a key or activating the instrument switch.
If Fluorescent Whiter Additive (FWA) compensated readings are to be
made, then this needs to be enabled with the correct command line
switches, and then setup for each paper white background
color, to establish an FWA reference. There is one FWA reference
locations
available for each alphabetic character not used for a special function
(ie. not H, K, N, Q, R, S),
keyed
to
the capital letters A-Z, allowing FWA corrected
comparisons between many different media.
Once a particular reference location is initialized with the FWA paper
color, subsequent readings triggered by using the corresponding lower
case letter a-z will use FWA
compensation for that keyed
location. Note that readings that are triggered some other way (ie.
using a non
alphabetic key, or using the instrument switch) will not be FWA
corrected readings.
If a non-FWA readings is to be performed, then a reading for a location
that has not been initialised for paper white should be used, or a non
alphabetic key (such as space or return) or instrument switch trigger
should be used.
If the instrument supports a high resolution spectral mode, then it can
be toggled on and off using the h
key.
If the instrument supports stored readings (ie. DTP20), then these can
be ignored using the n
key.
The previous reading can be stored as a reference, and delta E's
computed for each reading, using the r key.
A previous spectral reading can be saved in a spectrum CGATS file
(spectrum.sp) using the s key,
making this a convenient way of creating a custom illuminant spectrum.
A calibration can be initiated using the k key.