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.