spectro/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
-p
Use projector measurement mode (absolute results)
-pb
Use projector white brightness relative
measurement mode
-pw
Use projector white relative measurement mode
-e
Use emissive measurement mode (absolute results)
-a
Use ambient measurement mode (absolute results)
-f
Use ambient flash measurement mode (absolute results)
-y X
Display type - instrument specific list to choose from.
-i illum
Choose illuminant for
print/transparency spectral data:
A,
D50
(def.),
D65, F5, F8, F10 or file.sp
-Q observ
Choose CIE Observer for
spectral data or CCSS instrument:
1931_2 (def.), 1964_10, S&B 1955_2, shaw,
J&V 1978_2
-F filter
Set filter configuration:
n
None
p
Polarising filter
6
D65
u
U.V. Cut
-E extrafilterfile
Apply extra filter compensation file
-x
Display Yxy instead of Lab
-h
Display LCh instead of Lab
-V
Show running average and std. devation from ref.
-T
Display correlated color temperatures and CRI
-N
Disable auto calibration of instrument
-H
Use high resolution spectrum mode
(if available)
-X file.ccmx
Apply Colorimeter Correction Matrix
-X
file.ccss
Use
Colorimeter
Calibration
Spectral
Samples
for calibration
-X N
0: Technology (Display description)
1: etc.
-W n|h|x
Override
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 spotread
so as to display the usage information (i.e. "spotread -?" or
"spotread --"), 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 spotread.
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 -p flag
allows measuring in projector mode, using instruments that support
this mode. Values returned are absolute.
The -pb
flag allows measuring in projector 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 spotread.
The -pw
flag allows measuring in projector 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. An adaptive integration
time will be used in devices that support it. 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. An adaptive integration time will be used in
devices that support it.
The -f flag
allows measuring a flash with those instruments that support
scanning emissive measurements. The instrument needs to be triggered
by holding down its button, triggering the flash, then releasing the
button, similar to how a reflective strip is read.
The -y
flag allows setting the Display Type. Most colorimeters need this
parameter set to operate correctly. The selection typically
determines two aspects of of the instrument operation: 1) It may set the measuring mode
to suite refresh or non-refresh displays.
Typically only LCD (Liquid Crystal) displays have a non-refresh
nature. 2) It may select an
instrument calibration matrix suitable for a particular display
type. The selections available depends on the type and model of
instrument, and a list of the options for the discovered instruments
will be shown in the usage
information. For more details on what particular instruments support
and how this works, see Operation of
particular instruments.
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 -Q flag allows specifying a tristimulus
observer, and is used to compute PCS (Profile Connection Space)
tristimulus values. This is possible for a spectral instrument, or a
colorimeter that has CCSS capability. 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 -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 -E 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. [Note that this is currently only
supported by the Spectrolino driver.]
The -x option causes the reading to be
displayed as XYZ and Yxy values, rather than the default XYZ and
L*a*b*
The -h option causes the reading to be
displayed as XYZ and LCh values, rather than the default XYZ and
L*a*b*
The -V enables average and standard
deviation statistics on the L*a*b* values. This start and is reset
whenever a reference is taken ('r' key). This is useful in
quantifying repeatability.
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
tool 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 -X file.ccmx option reads
a Colorimeter Correction Matrix
from the given file, and applies it to the colorimeter instruments
readings. This can improve a colorimeters accuracy for a particular
type of display. A list of contributed ccmx files is here.
The -X file.ccss option reads
a Colorimeter Calibration
Spectral Sample from the given file, and uses it to set the
colorimeter instruments calibration. This will only work with
colorimeters that rely on sensor spectral sensitivity calibration
information (ie. the X-Rite i1d3,
or the DataColor Spyder4).This
can
improve
a
colorimeters accuracy for a particular type of display.
The -X N option selects a Colorimeter Calibration Spectral
Sample from the list of installed ccss files, rather than
specifying a specific ccss files as in the above usage. The CCSS
file that came with the i1d3 colorimeters can be installed using i1d3ccss, or one can be created and
installed using ccxxmake.
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. XYZ values are in
the range 0 .. 100 for reflective or transmissive readings, and
absolute cd/m^2 for display, emissive and ambient readings.
The L*a*b* values are computed relative to a D50 100 scale white
point. (Note that using display white relative mode makes the L*a*b
relative to the display white point.)
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.