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<h2><b>spectro/dispcal</b></h2>
<h3>Summary</h3>
Given calibration target information [white point, maximum brightness,
and
response curve ("gamma")], display a series of test patches on the
display, and using the colorimetric values read, create a calibration
lookup tables that make the display meet the desired target. The type
of instrument is determined by the communication port selected.
Emission and display measurement instruments are supported.<br>
<h3>Usage</h3>
<font size="-1"><span style="font-family: monospace;">dispcal [-options]</span><i
style="font-family: monospace;"> inoutfile</i><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#v">-v [n]</a><span
style="font-family: monospace;">
Verbose mode<br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#display">-display displayname</a><span
style="font-family: monospace;"> [X11 only] Choose X11 display name<br>
</span></font><font size="-1"><span style="font-family: monospace;"> <a
href="dispwin.html#dnm">-d n[,m]</a>
[X11
only]Choose the display from the following list (default 1),<br>
and optionally choose a different display m for VideoLUT access.</span></font><br>
<font size="-1"><span style="font-family: monospace;"> <a
href="dispwin.html#d">-d n</a>
Choose the display from the following list (default 1)</span></font><br
style="font-family: monospace;">
<font size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"></span> <span
style="font-family: monospace;"></span></font><small
style="font-family: monospace;"><span style="font-family: monospace;"></span><a
style="font-family: monospace;" href="dispread.html#c">-c listno</a><span
style="font-family: monospace;">
Set
communication port from the following list (default 1)<br>
</span></small><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="dispcal.html#r">-r</a><span
style="font-family: monospace;">
Report on the calibrated display then exit</span></font><font
size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"><br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#R">-R</a><span
style="font-family: monospace;">
Report on the uncalibrated display then exit</span></font><font
size="-1"><span style="font-family: monospace;"></span></font><br>
<font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#m">-m</a><span
style="font-family: monospace;">
</span></font><font size="-1"><span
style="font-family: monospace;">Skip</span><span
style="font-family: monospace;"> adjustment of the monitor
controls</span></font><br>
<font size="-1"><span style="font-family: monospace;"><a href="#o">-o
[profile.icm]</a><a href="#u_p1"></a> Create
fast matrix/shaper profile [different filename to outfile.icm]<br>
<a href="#O">-O description</a>
Fast ICC Profile Description string (Default "outfile")<br>
<a href="#u">-u</a>
Update previous calibration and (if -o used) ICC profile VideoLUTs</span><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"></span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#q">-q [lmh]</a><span
style="font-family: monospace;">
Quality
- Low, Medium (def), High<br>
<a href="#y">-y c|l</a>
Display type, c = CRT, l = LCD<br style="font-family: monospace;">
</span><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#t">-t [temp]</a><span
style="font-family: monospace;">
White Daylight locus target, optional target temperaturee in deg. K
(deflt.)<br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#T">-T [temp]</a><span
style="font-family: monospace;">
White Black Body locus target, optional target temperaturee in deg. K</span></font><br
style="font-family: monospace;">
<font size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#w">-w x,y</a><span
style="font-family: monospace;">
Set the target white point as chromaticity coordinates</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#b">-b bright</a><span
style="font-family: monospace;">
Set the target white brightness in cd/m^2</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#g">-g gamma</a><span
style="font-family: monospace;">
Set the target
response curve gamma (Def. 2.4)</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
Use "-gl" for L*a*b* curve</span><br style="font-family: monospace;">
<span style="font-family: monospace;">
Use "-gs" for sRGB curve<br>
Use "-g709" for REC 709 curve (should use -a as well!)<br>
Use "-g240" for SMPTE 240M curve </span></font><font size="-1"><span
style="font-family: monospace;">(should use -a as well!)</span></font><br>
<font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#G">-G gamma</a><span
style="font-family: monospace;">
Set
the target response curve actual technical gamma<br>
<a href="#f">-f [degree]</a>
Amount of black level accounted for with output offset (default all
input offset)<br>
<a href="#a">-a ambient</a>
Use viewing condition adjustment for ambient in Lux<br>
</span></font><font size="-1"><span style="font-family: monospace;"> <a
href="#k">-k
factor</a>
Amount to
try and correct black point hue. Default 1.0, LCD default 0.0<br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#B">-B bkbright</a><span
style="font-family: monospace;">
Set the target black brightness in cd/m^2</span></font><br
style="font-family: monospace;">
<font size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#e">-e [n]</a><span
style="font-family: monospace;">
Run n verify passes on final curves<br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#E">-E</a><span
style="font-family: monospace;">
Run only verify pass on installed calibration curves</span></font><br
style="font-family: monospace;">
<font size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"> <a href="#p">-p ho,vo,ss</a>
Position test window and scale it</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
ho,vi: 0.0 = left/top, 0.5 = center, 1.0 = right/bottom etc.</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
ss: 0.5 = half, 1.0 = normal, 2.0 = double etc.<br>
<a href="#F">-F</a>
Fill whole screen with black background<br
style="font-family: monospace;">
</span><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#n">-n</a><span
style="font-family: monospace;">
[X11 only] Don't set override redirect on test
window<br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="dispcal.html#K">-K</a><span
style="font-family: monospace;">
Run instrument calibration first<br>
</span></font><font size="-1"><span style="font-family: monospace;"> <a
href="dispcal.html#N">-N</a>
Disable auto calibration of instrument</span></font><br>
<font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#H">-H</a><span
style="font-family: monospace;">
Use high resolution spectrum mode (if
available)</span></font><font size="-1"><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"></span></font><br>
<font size="-1"><span style="font-family: monospace;"> <a href="#W">-W
n|h|x</a>
Ovride serial port flow control: n = none, h = HW, x = Xon/Xoff</span></font><font
size="-1"><span style="font-family: monospace;"><br>
</span></font><font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#D">-D [level]</a><span
style="font-family: monospace;">
Print debug diagnostics to stderr</span></font><br
style="font-family: monospace;">
<font size="-1"><span style="font-family: monospace;"></span><span
style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#p1"><i>inoutfile</i></a><span
style="font-family: monospace;">
</span><span style="font-family: monospace;">Base name for created or
updated </span></font><font size="-1"><a
style="font-family: monospace;" href="cal_format.html">.cal</a><span
style="font-family: monospace;"></span></font><font size="-1"><span
style="font-family: monospace;"> and <a
href="File_Formats.html#ICC">.icm</a> output files</span></font><br>
<br>
<h3>Comments<br>
</h3>
This is the utility is used for adjusting and calibrating a display to
reach
specified target behaviour, and optionally profiling it. For best
results on a CRT, you should
run this
against a neutral grey desktop background, and avoid having any bright
images or windows on the screen at the time you run dispcal. You could
also use the <span style="font-weight: bold;">-B</span> option to
black the whole screen out. <br>
<br>
<a name="v"></a> The <b>-v</b> flag reports progress information, as
well as other statistics about the progress of calibration. A numerical
argument greater than 1 gives greater verbosity.<br>
<br>
<a name="display"></a>When running on a UNIX based system that used the
X11
Windowing
System, <b>dispcal</b> will by default use the $DISPLAY environment
variable to determine which display and screen to read from. This can
be overridden by supplying an X11 display name to the <span
style="font-weight: bold;">-display</span> option. Note that if
Xinerama is active, you can't select the screen using $DISPLAY or
-display, you have to select it using the <span
style="font-weight: bold;">-d</span> parameter.<br>
<br>
<a name="d"></a> By default the main display will be the location of
the test window. If the system has more than
one display or screen, an alternate display/screen can be selected with
the <span style="font-weight: bold;">-d</span> parameter. If you
invoke <span style="font-weight: bold;">dispcal</span>
so as to display the usage
information (i.e. "dispcal -?" or "dispcal --"), then the discovered
displays/screens will be listed. Multiple displays may not be listed,
if they appear as a single display to the operating system (ie. the
multi-display support is hidden in the video card driver). On UNIX
based system that used the X11
Windowing
System, the <span style="font-weight: bold;">-d</span> parameter will
override the screen specified by the $DISPLAY or parameter.<br>
<br>
<span style="font-weight: bold;">Note</span> that on X11,
if the VideoLUTs for a display are not accessible, <span
style="font-weight: bold;">dispcal</span> will fail with an error.
This could be because you are trying to access a remote display, and
the remote display doesn't support the XF86VidMode extension, or
perhaps you are running multiple monitors using NVidia TwinView, or
MergedFB, and trying to access anything other than the primary monitor.
TwinView and MergedFB don't properly support the XF86VidMode extension
for multiple displays. You can use <a href="dispwin.html#r">dispwin -r</a>
to test whether the VideoLUTs are accessible for a particular display.
See also below, on how to select a different display for VideoLUT
access. Also note that dispcal will fail if the Visual depth doesn't
match the VideoLUT depth. Typically the VideoLUTs have 256 entries per
color component, so the Visual generally needs to be 24 bits, 8 bits
per color component.<br>
<br>
<a name="dnm"></a>Because of the difficulty cause by TwinView and
MergedFB in X11 based systems, you can optionally specify a separate
display number after the display that is going to be used to present
test patches, for accessing the VideoLUT hardware. This must be
specified as a single string, e.g. <span style="font-weight: bold;">-d
1,2</span>
. Some experimentation may be needed using <a href="dispwin.html">dispwin</a>
on such systems, to discover what
screen has access to the VideoLUT hardware, and which screens the test
patches appear on. You may be able to calibrate one screen, and then
share the calibration with another screen. Profiling can be done
independently to calibration on each screen.<br>
<br>
<a name="c"></a> <span style="font-weight: bold;">-c</span> The
instrument is assumed to communicate through a
USB or serial communication port, and the port can be selected with the
<b>-c</b>
option,
if the instrument is not connected to the first port. If you invoke <span
style="font-weight: bold;">dispcal</span>
so as to display the usage
information (i.e. "dispcal -?" or "dispcal --"), 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.<br>
<br>
<a name="r"></a> The -<span style="font-weight: bold;">r</span> and <span
style="font-weight: bold;"><a name="R"></a>-R </span>flags
perform a quick measurement of current display behaviour, reports
and then exits. If the <span style="font-weight: bold;">-r</span> flag
is used the measurement are taken using the currently loaded
calibration (Video LUT) curves. If <span style="font-weight: bold;">-R</span>
is use, then the uncalibrated ("raw" or "native") behaviour is
measured. Reported are: <br>
<br>
Black Brightness in cd/m^2<br>
White Brightness in cd/m^2<br>
The approximate Gamma<br>
The white point x,y chromaticity co-ordinates<br>
The correlated color temperature in Kelvin, and the
CIEDE200 to the Black Body locus.<br>
The correlated Daylight temperature in Kelvin, and
the CIEDE200 to the Daylight locus.<br>
The visual color temperature in Kelvin, and the
CIEDE200 to the Black Body locus.<br>
The visual Daylight temperature in Kelvin, and the
CIEDE200 to the Daylight locus.<br>
The visual color temperature in Kelvin<br>
(for <span style="font-weight: bold;">-R </span>"raw":)<br>
The apparent VideoLUT entry number of significant
bits.<br>
<br>
Note that the correlated color temperature is the temperature of a
black body radiator that has the closest color to the white point
measured using the traditional CIE 1960 UCS space color difference
formula. The correlated daylight temperature is a similar thing, except
the CIE daylight locus is used. The visual color temperature values are
calculated similarly to the correlated color temperatures, but using
the
modern CIEDE2000 color difference formula to calculate a better visual
approximation to the closest temperature to the displays white point.
There will be no difference between the UCS and CIEDE2000 temperatures
if the display white point actually lies on the particular locus.<br>
<br>
<a name="m"></a> The -<span style="font-weight: bold;">m</span> option
skips the usual process of adjusting the display monitor contrast,
brightness and white point controls, and skips straight to calibration.<br>
<br>
<a name="o"></a><span style="font-weight: bold;">-o [</span><span
style="font-style: italic;">profile.icm</span><span
style="font-weight: bold;">]</span> Normally <span
style="font-weight: bold;">dispcal</span> creates just a calibration
file, which can then be used for subsequent characterization using <a
href="dispread.html">dispread</a> and profiling using <a
href="colprof.html">colprof</a>. If the <span
style="font-weight: bold;">-o</span> flag is used, <span
style="font-weight: bold;">dispcal</span> will also create a
shaper/matrix profile. By default it will create a profile named <span
style="font-weight: bold;">inoutfile.icm</span>, but a differently
named file can be created or updated by specifying the name after the <span
style="font-weight: bold;">-o</span> flag. If the <span
style="font-weight: bold;">-u</span> flag is used with <span
style="font-weight: bold;">-o</span>, then the ICC profile <span
style="font-weight: bold;">vcgt</span> calibration curves will be
updated.<br>
<br>
<a name="O"></a>The <b>-O</b> parameter allows setting of the
shaper/matrix profile
description tag. The parameter should be a string that describes the
device and profile. With
most command line shells, it will be
necessary to enclose the parameter with double quotes, so that spaces
and other special characters are included in the parameter, and not
mistaken for the start of another flag, or as a final command line
parameter. Many programs that deal with ICC profiles use the
description tag to identify a profile, rather than the profile
filename, so using a descriptive string is important in being able to
find a profile. By default, the profile file name will
be used as the description.<br>
<br>
<a name="u"></a><span style="font-weight: bold;">-u</span> Normally <span
style="font-weight: bold;">dispcal</span>
creates a new calibration file and optional profile, based on the
requested targets and the
response of the display. This can take a fair amount of time,
particularly if a high quality level has been selected, so to speed up
the process of keeping a display in calibration the <span
style="font-weight: bold;">-u</span> flag can be used. This uses the
same calibration targets as the previous calibration but does a smaller
number of refinement passes, enough to improve the accuracy of the
calibration to account for drift in the device. If the <span
style="font-weight: bold;">-o</span> flag is used as well, then the
ICC
profile <span style="font-weight: bold;"></span>will have its vcgt tag
updated with the new
calibration. This keeps the profile up to date with the display.
Normally <span style="font-weight: bold;">dispcal -u</span> will use
the same quality level that was specified in the previous calibration,
but this can be overridden using the <span style="font-weight: bold;">-q</span>
flag. Any options that attempt to change the calibration target (ie.
white point, brightness, gamma etc.) will be ignored. Adjustment of the
display monitor controls is skipped.<br>
<br>
<a name="q"></a> Quality - Low, Medium (def), High. The <span
style="font-weight: bold;">-q</span> flag determines how much time and
effort to go to in calibrating the display. The higher the quality, the
more test readings will be done, the more refinement passes will be
done, the tighter will be the accuracy tolerance, and the more detailed
will be the calibration of the display. The result will ultimately be
limited by the accuracy of the instrument, the repeatability of the
display and instrument, and the resolution of the Video Lookup table
entries and Digital or Analogue output (RAMDAC).<br>
<br>
<a name="y"></a> Display type. Colorimeters can
do a more accurate job if they know what type of display technology
they are measuring. Use <span style="font-weight: bold;">-yc</span> if
you are
calibrating a CRT (Cathode Ray Tube) type monitor, and use <span
style="font-weight: bold;">-yl</span> if you are calibrating an LCD
(Liquid Crystal Display). A spectrometer instrument will not need this
option.<br>
<br>
<a name="t"></a><span style="text-decoration: underline;"></span>
<span style="font-weight: bold;">-t</span> Set the target white point
locus to the equivalent of a Daylight
spectrum of the given temperature in degrees Kelvin.
By default the white point target will be the native white of the
display, and it's color temperature and delta E to the daylight
spectrum locus will be shown during monitor adjustment, and adjustments
will be recommended to put the display white point directly on the
Daylight locus. If a Daylight color temperature is given as an argument
to <span style="font-weight: bold;">-t</span>, then this will become
the target of the adjustment, and the recommended adjustments will be
those needed to make the monitor white point meet the target.
Typical
values might be 5000 for matching printed output, or 6500, which gives
a brighter, bluer look. A white point temperature different to that
native to the display may limit
the maximum
brightness possible.<br>
<br>
<a name="T"></a><span style="text-decoration: underline;"></span>
<span style="font-weight: bold;">-T</span> Same functionality as
the <span style="font-weight: bold;">-t</span> option, except the
white point
locus will be the Black Body, or Planckian locus, rather than the
Daylight locus. While these two white point loci are quite close, they
are subtly different. If a temperature is given as an argument, this
will become the Black Body target temperature during adjustment.<br>
<br>
<a name="w"></a><span style="font-weight: bold;">-w</span> An
alternative to specifying a white point target in
Daylight or Black Body degrees Kevin, is to specify it in chromaticity
co-ordinates. This
allows the white point to be a color other than one on the Daylight or
Black Body. Note that the x,y numbers must be specified as a single
string
(no space between the numbers and the comma).<br>
<br>
<a name="b"></a><span style="font-weight: bold;">-b</span> Set
the
target brightness of white in cd/m^2. If
this number cannot be reached, the brightest output possible is chosen,
consistent with matching the white point target. Note that many of the
instruments are not particularly accurate when assessing the absolute
display brightness in cd/m^2. <span style="font-weight: bold;">NOTE</span>
that some LCD screens behave a little strangely near their absolute
white point, and may therefore exhibit odd behavior at values just
below white. It may be advisable in
such cases to set a brightness slightly less than the maximum such a
display is capable of.<br>
<br>
<a name="g"></a><span style="font-weight: bold;">-g gamma</span>
Set the
target response curve gamma. This is
normally an exponential curve (output = input ^gamma), and defaults to
2.4 on MSWindows and Linux/Unix (which is typical for a CRT type
display), and 1.8 on a Macintosh (OS X). Four pre-defined curves can be
used as well: the sRGB colorspace response curve, which is an
exponent curve with a
straight segment at the dark end and an overall response of
approximately gamma 2.2 (<span style="font-weight: bold;">-gs</span>),
the L* curve, which is the response of the CIE L*a*b* perceptual
colorspace (<span style="font-weight: bold;">-gl</span>). the REC 709
video standard response curve (<span style="font-weight: bold;">-g709</span>)
and the SMPTE 240M video standard response curve (<span
style="font-weight: bold;">-g240</span>) <br>
<br>
Note that a
real display can't reproduce any of these ideal curves, since it will
have a non-zero black point, whereas all the ideal curves assume zero
light at zero input. In the case of a gamma curve target, dispcal uses
an actual technical power curve shape that aims for the same relative
output at 50% input
as the ideal gamma power curve. To allow for the non-zero black level
of a real display, by default <span style="font-weight: bold;">dispcal</span>
will offset and scale the target curve so that zero input gives the
actual black level of the display (input offset). This ensures the most
visually even progression from display minimum, but this behavior can
be changed using the <span style="font-weight: bold;">-f</span> option
(see below).<br>
<br>
<span style="font-weight: bold;">Note</span> that many color spaces are
encoded with, and labeled as having a gamma of approximately 2.2 (ie.
sRGB, REC 709, SMPTE 240M), but are actually intended to be displayed
on a display with a typical CRT gamma of <span
style="font-weight: bold;">2.4</span>. This is because this 2.2 gamma
is a source gamma encoding in bright viewing conditions such as a
television studio, while typical display viewing conditions are quite
dark by comparison, and a contrast expansion of (approx.) gamma 1.1 is
desirable to make the images look as intended. So if you are displaying
video through the calibration, just setting the gamma curve to REC 709
is probably <span style="font-weight: bold;">not what you want!</span>
What you probably want to do, is to set the gamma curve to about gamma
2.4, so that the contrast range is expanded appropriately, or
alternatively use REC 709 but also use the <span
style="font-weight: bold;">-a</span> parameter to specify the ambient
viewing conditions, so that <span style="font-weight: bold;">dispcal</span>
can make an appropriate contrast enhancement. If your instrument is
capable of measuring ambient light levels, then you can do so during
the interactive display control adjustment.<br>
<br>
It is hard to know whether sRGB or Apple Macintosh computers should
also have such an adjustment, since it is not really possible to know
whether colors labeled as being in such a colorspace are actually
encoded in that gamma with the expectation that they will be displayed
on a display with that actual response, or whether they are intended to
be displayed on a display that contrast expands by a power 1.1.
Both situations might be the case, depending on how source material is
created!<br>
<br>
<a name="G"></a><span style="font-weight: bold;">-G gamma</span>
As explained above, the gamma value provided to the <span
style="font-weight: bold;">-g</span> option is used to set and actual
response curve that makes an allowance for the non-zero black of the
actual display, and will have the same relative output at 50% input as
the ideal gamma power
curve, and so best matches typical expectations. The <span
style="font-weight: bold;">-G</span> option is an alternative that
allows
the <span style="font-weight: bold;">actual</span> power to be
specified instead, meaning that when combined with the displays
non-zero black value, the response at 50% input
will probably not match that of the ideal power curve with that gamma
value.<br>
<br>
<a name="f"></a><span style="font-weight: bold;">-f [degree]</span>: As
explained in for the <span style="font-weight: bold;">-g</span> and <span
style="font-weight: bold;">-G</span> options, real displays do not
have a zero black response, while all the target response curves do, so
this has to be allowed for in some way. The default way of handling
this (equivalent to -f 0) is to offset and scale the input values
into the ideal response
curve so that zero input gives the actual non-zero display response.
This ensures the most visually even progression from display minimum.
The other alternative is to allow for this at the output of the ideal
response curve, by offsetting and scaling the output values.<span
style="font-weight: bold;"></span> This can be done by using the <span
style="font-weight: bold;">-f</span> option. This will probably give a
less progressive response from black, but may better match the
responses that other systems provide. A further subtlety is to provide
a split between how much of the offset is accounted for as input to the
ideal response curve, and how much is accounted for at the output, and
this can be done by providing a parameter <span
style="font-weight: bold;">-f degree</span>, where the degree is 0.0
accounts for it all as input offset, and 1.0 accounts for all of it as
output offset.<br>
<br>
<a name="a"></a><span style="font-weight: bold;">-a ambient</span>: As
explained for the <span style="font-weight: bold;">-g</span>
parameter, often colors are encoded in a situation with viewing
conditions that are quite different to the viewing conditions of a
typical display, with the expectation that this difference in viewing
conditions will be allowed for in the way the display is calibrated.
The <span style="font-weight: bold;">-a</span> option is a way of
doing this. By default <span style="font-weight: bold;">dispcal</span>
will not make any allowances for viewing conditions, but will calibrate
to the specified response curve, but if the <span
style="font-weight: bold;">-a</span> option is used, or the ambient
level is measured during the interactive display controls portion of
the calibration, an appropriate viewing conditions adjustment will be
performed. For a gamma value or sRGB, the original viewing conditions
will be assumed to be that of the sRGB standard viewing conditions,
while for REC 709 and SMPTE 240M they will be assumed to be television
studio viewing conditions. By specifying or measuring the ambient
lighting for your display, a viewing conditions adjustment based on the
CIECAM02 color appearance model will be made for the brightness
of your display and the contrast it makes with your ambient light
levels. <br>
<br>
<a name="k"></a><span style="font-weight: bold;">-k</span> Normally
dispcal will attempt to make all colors
down the neutral axis (R=G=B) have the same hue as the chosen white
point (equivalent to <span style="font-weight: bold;">-k 1.0</span>).
Near the black point, red, green or blue can only be added, not
subtracted from zero, so the process of making the near black colors
have the desired hue, will <span style="font-weight: bold;">lighten</span>
them to some extent. For a device
with a good contrast ratio or a black point that has nearly the same
hue as the white, this is not a problem. If the device contrast ratio
is not so good, and the black hue is noticeably different to that of
the chosen white point (which is often the case for <span
style="font-weight: bold;">LCD</span> type displays, or <span
style="font-weight: bold;">CRT</span> type displays with one channel
which has a poor level of black), this could have
a noticeably detrimental effect
on an already limited contrast ratio, and result in a black that is not
as good as it can be. The <span style="font-weight: bold;">-k</span>
flag allows the amount of black
point hue correction to be controlled. By default a factor of <span
style="font-weight: bold;">1.0</span> will be used, which is usually
good for <span style="font-weight: bold;">CRT</span> and also by
default a factor of <span style="font-weight: bold;">0.0</span> is
used for <span style="font-weight: bold;">LCD</span>
type displays, but the <span style="font-weight: bold;">-k</span>
option allows overriding these with a custom value between 0.0 (no
correction) to 1.0 (full correction). If less than full correction is
chosen, then the resulting calibration curves will have the target
white point down most of the curve, but will then cross over to the
native or compromise black point that is blacker, but not of the right
hue.<br>
<br>
<a name="B"></a><span style="font-weight: bold;">-B</span> Set
the
target brightness of black in cd/m^2. Setting too high a value may give
strange results as it interacts with trying to achieve the target
"advertised" gamma curve shape. You could try using -f 1 if this causes
a problem.<br>
<br>
<a name="e"></a><span style="font-weight: bold;">-e [n]</span> Run <span
style="font-weight: bold;">n</span> verify
passes on the final curves. This
is an extra set of instrument readings, that can be used to estimate
how
well the device will match the targets with the computed calibration
curves. Note that the usefulness of the verification is sometimes
limited by the repeatability of the device & instrument readings.
This
is often evident for CRT displays, which (due to their refresh rate)
flicker. More than one verification pass can be done by providing the
parameter <span style="font-weight: bold;">n</span>, and by then
comparing the successive verifications, some idea of the repeatability
can be ascertained. The verification uses a fixed number of semi-random
test values to test the calibration.<br>
<br>
<a name="E"></a><span style="font-weight: bold;">-E</span> Run verify
pass on the display as it is
currently setup (currently installed LUT curves). This will use the
usual input
parameters to establish the expected (target) characteristic. <span
style="font-weight: bold;">Note</span> that if the initial calibration
was modified due to it being out
of gamut of the display, verify will show the resulting discrepancy.
You can
use <a href="dispwin.html">dispwin</a> to load a <span
style="font-weight: bold;">.cal</span> file into the display before
running dispcal <span style="font-weight: bold;">-E</span>. Note that
on Apple OS X, you will need to run dispwin with the <a
href="dispwin.html%20#x">-x</a> option <span
style="font-weight: bold;"></span>to ensure that the calibration is
retained while dispcal <span style="font-weight: bold;">-E</span> is
run. <br>
<br>
<a name="p"></a> The <span style="font-weight: bold;">-p</span>
parameter allows you to position and size the test patch window. By
default it is places in the center of the screen, and sized
appropriately for the type of instrument. The <span
style="font-weight: bold;">ho</span> and <span
style="font-weight: bold;">vo</span> values govern the horizontal and
vertical offset respectively. A value of 0.0 positions the window to
the far left or top of the screen, a value of 0.5 positions it in the
center of the screen (the default), and 1.0 positions it to the far
right or bottom of the screen. The <span style="font-weight: bold;">ss</span>
parameter is a scale factor for the test window size. A value of 0.5
for instance, would produce a half sized window. A value of 2.0 will
produce a double size window. Note that the ho,vo,ss numbers must be
specified as a single string (no space between the numbers and the
comma).<br>
For example, to create a double sized test window at the top right of
the screen, use <span style="font-weight: bold;">-p 1,0,2</span> .<br>
<br>
<a name="F"></a> The <span style="font-weight: bold;">-F</span>
flag causes the while screen behind the test window to be masked with
black. This can aid black accuracy when measuring CRT displays or
projectors.<br>
<br>
<a name="n"></a><span style="font-weight: bold;">-n</span> When running
on a UNIX based system that used the X11
Windowing
System, <b>dispcal</b> normally selects the override redirect so that
the
test window will appear above any other windows on the display. On some
systems
this can interfere with window manager operation, and the <b>-n</b>
option
turns this behaviour off.<br>
<br>
<a name="K"></a> The -<span style="font-weight: bold;">K</span> option
runs through the black and sensor
relative
calibration routines for the Xrite DTP92 and DTP94 instruments, the
black level calibration for the Eye-One Display 1, and a CRT frequency
calibration for the Eye-One Display 2. For the
black calibration the instrument should be placed on an opaque, black
surface, and any stray light should be avoided by placing something
opaque over the instrument. If a
Spectrolino
is being used, then a white and black calibration will always be
performed before
the instrument can be placed on the display, unless the <a
href="dispcal.html#N">-N</a>
flag is used. Generally it is not necessary to do a calibration every
time an instrument is used, just now and again. There is also no point
in
doing a CRT frequency calibration, as this will be done
automatically at the commencement of patch reading, and will be lost
between runs.<br>
<br>
<a name="N"></a>The <b>-N</b> 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.<br>
<br>
<a name="H"></a> The -<span style="font-weight: bold;">H</span> option
turns on high resolution spectral mode, if the instrument supports it,
such as the Eye-One Pro.
See <a href="instruments.html">Operation of particular instruments</a>
for more details. This may give better accuracy for display
measurements.<br>
<br>
<a name="W"></a>The <b>-W</b> <span style="font-weight: bold;">n|h|x</span>
parameter overrides the default serial communications
flow control setting. The value <span style="font-weight: bold;">n</span>
turns all flow control off, <span style="font-weight: bold;">h</span>
sets hardware handshaking, and <span style="font-weight: bold;">x</span>
sets Xon/Xoff handshaking. This commend may be useful in workaround
serial communications issues with some systems and cables. <br>
<br>
<a name="D"></a>The <b>-D</b> 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.<br>
<br>
<a name="p1"></a><span style="font-weight: bold;">inoutfile</span> The
final parameter on the command line is the base
filename for the <a href="cal_format.html">.cal</a>
file and the optional ICC profile. Normally this will be created (or an
existing file will be
overwritten). If the <span style="font-weight: bold;">-u</span> flag
is used, then these files will be updated. If a different ICC profile
name needs to be specified, do so as an argument to the <span
style="font-weight: bold;">-o</span> flag.<br>
<br>
<span style="font-weight: bold;">NOTE</span> that on an X11 system, if
the environment variable <span style="font-weight: bold;">ARGYLL_IGNORE_XRANDR1_2</span>
is set (ie. set it to "yes"), then the presence of the XRandR 1.2
extension will be ignored, and other extensions such as Xinerama and
XF86VidMode extension will be used. This may be a way to work around
buggy XRandR 1.2 implementations.<br>
<br>
<hr style="width: 100%; height: 2px;"><br>
<a name="Adjustment"></a>The adjustment of the display controls
(brightness, contrast, R, G
& B channel controls etc.) is very dependent on the particular
monitor. Different types and brands of monitors will have different
controls, or controls that operate in different ways. Some displays
have almost no user controls, and so you may well be best skipping
display adjustment, and going straight to calibration.<br>
<br>
Almost all LCD displays lack a real <span style="font-weight: bold;">contrast</span>
control. Those that do
present such a control generally fake it by adjusting the video
signal. For this reason it is usually best to set an LCD's <span
style="font-weight: bold;">contrast</span> control at its neutral
setting (ie. the setting at which it doesn't change the video signal).
Unfortunately, it can be hard to know what this neutral setting is. On
some displays it is 50%, others 75%. If the LCD display has a "reset to
factory defaults" mode, then try using this first, as a way of setting
the <span style="font-weight: bold;">contrast</span> control to
neutral. The LCD <span style="font-weight: bold;">brightness</span>
control generally adjusts the level of backlighting the display gets,
which affects the maximum brightness, and also tends to raise or lower
the black level in proportion, without changing the displays response
curve shape or overall contrast ratio. If your LCD display has a <span
style="font-weight: bold;">backlight</span> control as well as a <span
style="font-weight: bold;">brightness</span> control, then the
brightness control is also probably being faked, and you are probably
better off setting it to it's neutral setting, and using the <span
style="font-weight: bold;">backlight</span> control in place of <span
style="font-weight: bold;">brightness</span> in the following
adjustments.<br>
<br>
On CRT based displays, the <span style="font-weight: bold;">brightness</span>
control generally adjusts the black level of the display (sometimes
called the <span style="font-weight: bold;">offset</span>), and as a
side
effect, tends to change the maximum brightness too. A CRT <span
style="font-weight: bold;">contrast</span> control generally adjusts
the maximum brightness (sometimes called <span
style="font-weight: bold;">gain</span>) without affecting the black
level a great deal.
On a CRT both the <span style="font-weight: bold;">brightness</span>
and <span style="font-weight: bold;">contrast</span> controls will
tend to affect the shape or gamma of the display response curve.<br>
<br>
Many displays have some sort of color temperature adjustment. This may
be in the form of some pre-set color temperatures, or in the form of
individual Red, Green and Blue channel gain adjustments. Some CRT
displays
also have R, G & B channel offset adjustments that will affect the
color temperatures near black, as well as affect the individual
channels curve shape. The color
temperature adjustment will generally affect the maximum brightness,
and may also affect the black level and the shape of the display
response curves.<br>
<br>
Some special (expensive) LCD displays may have a white point
adjustment that changes the color of the backlight. If you do not have
one of these types of LCD displays, then attempting to change the white
point of the display (even if it appears to have a "<span
style="font-weight: bold;">white point selection</span>" or <span
style="font-weight: bold;">R/G/B</span> "<span
style="font-weight: bold;">gain</span>" controls") may not be a good
idea, as once again these controls are probably being faked by
manipulating the signal levels. Even if you do manage to change the
white point significantly, it may do things like change the mid tone
color too dramatically, or create a display response that is hard to
correct with calibration, or results in side effects such as
quantization (banding) or other undesirable effects. You may have to
try out various controls (and your aim points for the display
calibration), to decide what is reasonable to attempt on an LCD display.<br>
<br>
Due to the variety of controls as well as the interaction between them,
it can be an iterative process to arrive at a good monitor set-up,
before proceeding on to calibrating and profiling a display. For this
reason, <span style="font-weight: bold;">dispcal</span> offers a menu
of adjustment modes, so that the user can interactively and
iteratively adjust the display controls to meet the desired targets.<br>
<br>
1) Black level (CRT: Brightness)<br>
2) White point (Color temperature, R,G,B, Gain/Contrast)<br>
3) White level (CRT: Gain/Contrast, LCD: Brightness/Backlight)<br>
4) Black point (R,G,B, Offset/Brightness)<br>
5) Check all<br>
6) Measure and set ambient for viewing condition adjustment<br>
7) Continue on to calibration<br>
8) Exit<br>
<br>
There are four basic adjustment modes. Normally one would proceed
through them in the order above, then perhaps repeat the first
adjustment, before
checking the overall settings. The White point and White level modes
operate slightly differently, depending on whether a white target point
has been set using the <span style="font-weight: bold;">-t -T</span>
or <span style="font-weight: bold;">-w</span> options, and on whether
a brightness target has been set using the <span
style="font-weight: bold;">-b</span> option.<br>
<br>
<br>
The first mode lets you adjust the black level of a CRT display. Given
the
current white level, it calculates a value that should produce a 1%
display brightness if the black level is set correctly. After doing
some initial measurements, it will show the target brightness value (in
cd/m^2) on one line, and then underneath it will show continuously
updated readings from the
display. The left most character will switch from '\' to '/' or back
again each time a reading is updated. Some instruments can be quite
slow in measuring dark colors, and it's best to wait for a reading
update before changing the controls more than once. Underneath the
target value is
displayed the current reading, and to the right of this is a '+', '-'
or '=' symbol, which gives a hint as to which way to adjust the
brightness control to improve the match to the target.<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">
Adjust CRT brightness to get target level. Press space when done.</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Target 0.60</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> / Current 0.68 -</span></small><br>
<br>
Once happy with the adjustment, press space to go back to the menu.<br>
<br>
<br>
The second mode lets you adjust the color of the white point of the
display.
If a target white point has been set, it will show the target
brightness value (in
cd/m^2) on one line, together with the target chromaticity co-ordinates
for the white point, and then underneath it will show continuously
updated readings from
the display. The left most character will switch from '\' to '/' or
back again each time a reading is updated. Underneath the target
brightness value is
displayed the current reading, and then the current chromaticity
co-ordinate values. To the right of this is the current delta E of the
white point from the target, and further to the right are hints '+',
'-'
or '=' as to which direction to adjust the individual Red, Green
and Blue gain settings to move the white point in the direction of the
target.
If the symbol is doubled, then this channel will have the greatest
effect. If you do not have individual channel gain controls, then try
choosing amongst color temperature pre-sets, to find one with the
lowest delta E.<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">Adjust
R,G & B gain to get target x,y. Press space when done.<br>
Target B 60.00, x 0.3451, y 0.3516<br>
/ Current B 60.05, x 0.3426, y 0.3506 DE 1.4
R+ G+ B--</span><span style="font-family: monospace;"></span></small><br>
<br>
If you did not set a white point target, then the information shown is
a little
different - it will show
the initial
white point value, as well as the color temperature, and the CIEDE2000
of the white point to either the Daylight or Black Body locus
(depending on whether the <span style="font-weight: bold;">-T</span>
flag was set). The constantly updated values show the same thing, and
the Red, Green and Blue control hints show the direction to adjust the
controls to place the white point on the locus. The control that will
have the most direct effect on the color temperature will be the Blue,
while the Green will most directly move the white point towards or away
from the locus, thereby reducing the delta E of the white point to the
locus (but there is interaction).<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">Adjust
R,G & B gain to desired white point. Press space when done.</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Initial B 47.25, x 0.3417,
y 0.3456, CDT 5113 DE 6.9</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">\ Current B 47.38, x 0.3420, y
0.3460 CDT 5104 DE 6.7 R-- G+ B-</span></small><br>
<br>
The brightness value is just there as a guide to what effect the
adjustment is having on the overall brightness. Usually the white level
brightness is adjusted using the next adjustment mode. Once happy with
the adjustment, press space to go back to the menu.<br>
<br>
<br>
The third mode lets you adjust the brightness of white on the
display. If you set a target brightness using the <span
style="font-weight: bold;"><span style="font-weight: bold;">-b</span></span>
parameter, it will show the target brightness value (in
cd/m^2) on one line, and then underneath it will show continuously
updated readings from the
display. The left most character will switch from '\' to '/' or back
again each time a reading is updated. Underneath the target value is
displayed the current reading, and to the right of this is a '+', '-'
or '=' symbol, which gives a hint as to which way to adjust the CRT
contrast or LCD brightness control to improve the match to the target.<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">Adjust
CRT Contrast or LCD Brightness to get target level. Press space when
done.<br>
Target 60.00<br>
/ Current 59.96 +</span><span
style="font-family: monospace;"></span></small><br>
<br>
If you did not set a brightness target, it will show the initial
brightness as the target, and the current brightness, which you can
then set any way you want:<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">Adjust
CRT Contrast or LCD Brightness to desired level. Press space when done.</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Initial 47.32</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">/ Current 47.54</span></small><br>
<br>
Once happy with the adjustment, press space to go back to the menu.<br>
<br>
<br>
The fourth mode lets you adjust the color of the black point of the
display, if the display has Red, Green and Blue channel offset
controls.
It will show the target 1% brightness value (in
cd/m^2) on one line, together with the target chromaticity co-ordinates
for the black point, and then underneath it will show continuously
updated readings from
the display. The left most character will switch from '\' to '/' or
back again each time a reading is updated. Underneath the target
brightness value is
displayed the current reading, and then the current chromaticity
co-ordinate values. To the right of this is the current delta E of the
black point from the target, and further to the right are hints '+',
'-'
or '=' as to which direction to adjust the individual Red, Green
and
Blue offset settings to move the black point in the right direction. If
the symbol is doubled, then this channel will have the greatest effect.
<br>
<br>
<span style="font-family: monospace;"><span style="font-weight: bold;">
Adjust R,G & B offsets to get target x,y. Press space when done.<br>
Target B 0.60, x 0.3451, y 0.3516<br>
\ Current B 0.62, x 0.2782, y 0.2331 DE 10.3
R+ G++ B-</span></span><small style="font-weight: bold;"><span
style="font-family: monospace;"></span><span
style="font-family: monospace;"></span></small><br>
<br>
The 1% brightness value is just there as a guide to what effect
the
adjustment is having on the 1% brightness level. The combined channel
offsets may have an effect on this in combination with the CRT
brightness control. Press space to go back to the menu.<br>
<br>
<br>
The fifth selection checks on the overall settings. If targets
have been set, it will be like:<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">
Target Brightness = 50.00, Current = 47.44, error = -5.1%<br>
Target 50% Level = 10.32, Current = 8.10, error =
-4.4%<br>
Target Near Black = 0.47, Current = 0.68, error
= 0.4%<br>
Target white = x 0.3458, y 0.3586, Current = x 0.3420, y 0.3454,
error = 7.55 DE<br>
Target black = x 0.3458, y 0.3586, Current = x 0.2908, y 0.2270,
error = 29.69 DE</span><span style="font-family: monospace;"></span></small><br>
<br>
or if no targets are set:<br>
<br>
<small style="font-weight: bold;"><span style="font-family: monospace;">
Current Brightness = 46.28</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> Target 50% Level =
10.07, Current = 7.52, error = -5.5%</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Target Near Black =
0.46, Current = 0.46, error = -0.0%</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Current white = x 0.3439,
y 0.3466, VCT 5098K DE 3.0</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> Target black = x 0.3439, y
0.3466, Current = x 0.3093, y 0.2165, error = 30.30 DE</span></small><br>
<br>
and will then go back to the menu.<br>
<br>
Once you're happy with the display set-up, you can either proceed
on to the rest of the calibration by selecting <span
style="font-weight: bold;">7)</span>, or exit and re-start by
selecting <span style="font-weight: bold;">8)</span>. You might want
to re-start if you want to change the calibration targets.<br>
<br>
The seventh selection <span style="font-weight: bold;">7)</span>
allows the reading of you ambient lighting conditions if your
instrument supports such a mode. Doing so will enable the <span
style="font-weight: bold;">-a</span> option to compensate for your
viewing conditions. See <a href="#a">-a</a>.<br>
<br>
<hr style="width: 100%; height: 2px;">NOTE
that some <span style="font-weight: bold;">LCD</span> screens behave a
little strangely near their absolute
white point, and may therefore exhibit odd behavior at values just
below white. It may be advisable in
such cases to set a brightness slightly less than the maximum such a
display is capable of.<br>
<br>
The program attempts to stop any screensaver or
powersaver from interfering with the measurements, but this may not be
effective on some systems, so it may be necessary to manually disable
the screensaver and/or powersaver before commencing
the calibration with a large number of patches.<br>
<br>
The calibration tables produced maintain the maximum level of precision
available on a system. If the system RAMDAC (Video Lookup Tables and
Digital To Analog Converted) outputs are better than 8
bits per component, then the resulting curves can reflect this,
although few current operating systems and/or display cards actually
support better than 8 bit per component output.<br>
<br>
If communications break down with a USB connected instrument, you may
have to unplug it, and plug it in again to recover operation.<br>
<br>
Some systems (Apple OSX in particular) have a special set of user
interface controls ("Universal Access") that allows altering the
display in ways designed to assist visually impaired users, by
increasing contrast etc. This will interfere badly with any attempts to
calibrate or profile such a system, and must be turned off in order to
do so. Note that certain magic
keyboard sequences can turn this on by accident.<br>
<br>
<br>
<br>
<br>
<br>
</body>
</html>
distrib
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Mandriva
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2010.0
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i586
>
media
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contrib-release
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by-pkgid
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56e231b080a119bc733fcd74872c9f3d
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files
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239
