spotread

spectro/spotread

Summary

Use an instrument to read a single color value. This can be a useful diagnostic aid.

[ A commercial tool that does much of what spotread does and more, is the ArgyllPRO ColorMeter. ]

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
-e                    Use emissive measurement mode (absolute results)
-eb                   Use display white brightness relative measurement mode
-ew                   Use display white point relative chromatically adjusted mode
-p                    Use telephoto measurement mode (absolute results)
-pb                   Use projector white brightness relative measurement mode
-pw                   Use projector white point relative chromatically adjusted mode
-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      Set simulated instrument illumination using FWA (def -i illum):
               M0, M1, M2, A, D50 (def.), D50M2, D65, F5, F8, F10 or file.sp
-i illum      Choose illuminant for computation of CIE XYZ from spectral reflectance & FWA:
               A, D50 (def.), D50M2, 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, CRI and TLCI
-N                    Disable initial calibration of instrument if possible
-O                    Do one cal. or measure and exit
-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
-Y r|n                Override refresh, non-refresh display mode
-Y R:rate             Override measured refresh rate with rate Hz
-Y A                  Use non-adaptive integration time mode (if available).
-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 Graph plots light wavelength on the X axis, and either absolute or relative level on the Y axis.

Measurement Mode	Y Units
Emission	mW/(m².sr.nm)
Ambient	mW/(m².nm)
Emission Flash	mW/(m².sr.nm.s)
Ambient Flash	mW/(m².nm.s)
Reflective	%/nm
Transmissive	%/nm

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 -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 by default (see the -ZA flag). Values returned are absolute.

The -eb flag allows measuring in emission mode using instruments that support this mode, with the brightness reading being relative 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 -ew flag allows measuring in emissive mode using instruments that support this mode, with the reading being relative to the white value read as the first reading using a Bradford chromatic adaption. This matches the absolute <-> relative intent transformation of Argyll ICC profiles.

The -p flag allows measuring in telephoto mode, using instruments that support this mode, e.g. the ColorMunki. Values returned are absolute.
Note that you would use normal emissive mode to measure projectors using instruments without a specific telephoto mode.

The -pb flag allows measuring in telephoto mode using instruments that support this mode, with the brightness reading being relative 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 telephoto mode using instruments that support this mode, with the reading being relative to the white value read as the first reading using a Bradford chromatic adaption. This matches the absolute <-> relative intent transformation of Argyll ICC profiles.

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. 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. 3) Any installed CCSS files (if applicable), or CCMX files. These files are typically created using ccxxmake, and installed using oeminst. The default and Base Calibration types will be indicated in the usage.

The -I parameter allows specifying a standard or custom illumination spectrum to be used as the simulated reflectance instrument illuminant when FWA compensation is used during measurement, overriding the default D50 or CIE computation illuminant used for FWA (see -i below). If using M0, M1 or M2, then the -i option is not normally used. See colprof -f for a fuller explanation.

The -i parameter allows specifying a standard or custom reflectance illumination spectrum applied to reflective or transmissive spectral data to compute CIE tristimulus values. A, D50, D50M2, D65, F5, F8, F10 are a selection of standard illuminant spectrums, with D50 being the default. If using -I M0, M1 or M2, then this -i option is not normally used. If a filename is specified instead, it will be assumed to be an Argyll specific .sp spectrum file. If FWA compensation is used during measurement, this illuminant will be used by default as the simulated instrument illuminant.

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 XYZ and L*a*b* values. This start and is reset whenever a reference is taken ('r' key). A side effect of this option is to disable the clamping of XYZ and L*a*b* value to positive, so that a valid average of black can be obtained.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) including the R9 value, plus the TLCI (Qa) is also computed if the instrument is capable of spectral measurement. If the notation (Invalid) is displayed after the CRI or TLCI, then this means that the the spectrum white point is to far from the black body and Daylight locus to be meaningful.

-N Any instrument that requires regular calibration will ask for calibration on initial start-up. Sometimes this can be awkward if the instrument is being mounted in some sort of measuring jig, or annoying if several sets of readings are being taken in quick succession. The -N suppresses this initial calibration if a valid and not timed out previous calibration is recorded in the instrument or on the host computer. It is advisable to only use this option on the second and subsequent measurements in a single session.

-O Do a calibration or a single measurement and exit. To take a measurement with an instrument that always does a calibration first, calibrate it and then use -O with -N. The -O option is intended to simplify scripted use of spotread.

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 & Spyder5).This can improve a colorimeters accuracy for a particular type of display.

The -Y r and -Y n options overrides the refresh display mode set by the -y display type selection, with -Y r forcing refresh display mode, and -Y n forcing a non-refresh display mode. Not all instruments support a display measurement refresh mode, or the ability to override the mode set by the display type selection.

The -Y R:rate options overrides calibration of the instrument refresh rate. This may be useful if the instrument supports this function and the refresh rate cannot be accurately calibrated from the display itself.

The -Y A option uses a non-adaptive integration time emission measurement mode, if the instrument supports it, such as the Eye-One Pro, ColorMunki, i1d3 or K10. By default an adaptive integration time measurement mode will be used for emission measurements, but some instruments support a fixed integration time mode that can be used with display devices. This may give faster measurement times, but may also give less accurate low level readings.

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.

By default the L*a*b* values are computed relative to a fixed D50 100 scale white point, so values for emissive sources are not particularly useful.
Using the display white relative mode uses a Bradford chromatic transform to transform from the measured white to a D50 white (the same as ArgyllCMS ICC profile deals a display white), and then computes the D50 L*a*b from that.

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, F), 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 a laser target (such as the JETI specbos), then this can be toggled on & off using the t key. It will automatically be turned off at each measurement.

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.

For instruments that support it and are in a refresh display mode, the calibrated refresh rate can be read back using the f key.

For instruments that support it and are in an emissive measurement mode, a display refresh rate measurement can be made by using the F key.