Monitor Tab Help Window
LProf is an open source application that creates ICC profile
for cameras, scanners and monitors/displays.
Create a Monitor Profile
LProf can work in two
different modes to generate a monitor profile. The "advanced" mode,
that gives accurate
profiles by using hardware devices like X-Rite DP92 or GretagMacbeth
EyeOne,
and the "simple" mode, that allow to you build reasonably accurate
profiles without any additional hardware.
Building a monitor profile: a coarse
approximation
Let's build our first monitor profile to check how all this
stuff works. We don't need great accuracy at this point. We want to
create an approximation, just to visually check if all is going
OK.
First start LProf. Since we
need only a coarse profile on the "Monitor
Profiler"
tab select the radio button labeled: "Build a coarse profile,
giving approximate values". This is selected by default. We
do not need any hardware measurements at this point only a few visual
adjustments. Press the button labeled: "Enter
monitor values". You will see
the monitor values dialog.
Step 1: Set contrast
In order to obtain maximum
performance, we need to adjust the physical monitor
controls.
Set contrast to near maximum, (yes, near maximum. This is the
gain of the monitor and we need as much gain as the monitor can
deliver).
Step 2: Set Gamma and Black Point
Now select the "Set Gamma and Black Point"
button. This dialog will help you to set both the gamma and black
point for your monitor.
Step 4: Set White Point
For information on setting monitor White Point see Rough Monitor Values.
Step 5: Set Primaries
Next adjustment is setting the primaries. For
information on setting Monitor Primaries values see Rough Monitor Values.
Step 6: Make Final Settings and Create Profile
Now you can use the "Profile
Identification"
dialog to fill in the info about your monitor. Although this is not
strictly required, it could prevent a lot of confusion when you have
more than a couple of profiles. It is important to include unique information
in the "Description"
field of this dialog since this information is used by many
applications, including LProf, to list profiles for users. Now we are ready to generate our
profile. We must specify the output filename just like you did when
creating a camera/scanner profile. For the name, we could use
something like "CoarseMonitor.icm". Type in the name and then proceed to
generate the profile by pressing
the "Create Profile" button. If all is OK, the status console will show
"Profile DONE!". Let's now check how well the profile is working
by eye.
Do this is basically the same way you proofed your scanner profile.
Building a Monitor Profile: Using a Hardware Measurement
Device.
Starting with LProf version 1.11.5 display calibration and
profiling hardware measurement devices are now supported. LProf
supports the following hardware devices for calibrating and profiling
displays:
- GretagMacbeth EyeOne Display
- GretagMacbeth EyeOne Display LT
- GretagMacbeth EyeOne Display 2
- GretagMacbeth EyeOne Pro
- GretagMacbeth Spectrolino
- X-Rite DTP-92
- X-Rite DTP-94
Supported USB devices are automatically detected and will be listed in the Select Instrument: combo on the Display Calibration and Measurement dialog. Devices that use a serial port need to be configured in the Serial Measurement Device Setup area on the Preferences tab. Most of the supported devices are USB devices.
The first step to create an accurate profile is the calibrate
and measure the monitor. This is done either by using one of the
measurement devices supported by LProf or by using an external program
with some other device to calibrate and measure the display. This
document will describe both ways of doing this but will put more
emphases on using a supported measurement device because this will
allow you to achive a better display calibration.
Calibrate and Measure Using a Supported Measurement Device
This is handled by the Display Calibration and Measurement dialog so
please refer to the documnetation that covers it for more detail.
That dialog will allow you to do a number of important operations
that will result in your display being properly adjusted (calibrated)
and measured so that a profile can be created.
When you have completed running the Display Calibration and Measurement dialog two
measurement files will have been created. These will contain the
video card gamma table data, called a Calibration Sheet, and the
profiling measurement data, called a Measurement Sheet. The Calibration Sheet data will
be used to create a VCGT tag in the profile which will be used to load
the video card gamma tables to get the correct gamma and also to get
the right color balance for the whole tonal range of the display.
The Measurement Sheet data will be used to create the
color look up tables in the profile. Unlike most commerical
profiling software LProf does not come with it's own gamma loader but
X11 users can use xcalib, Windows users can use either xcalib or
the Windows Color Control Panel Applet and Mac users can use ColorSync.
These files will appear in the Measurement Sheet and Calibration Sheet
entry boxes that appear below the "Use externally generated files"
radio button. When using an LProf supported measurement device
these are grayed out and can not be changed by a user.
Create the Profile
First in the "Output profile file",
select a new file name for your profile. Please use a name that
ends in .icm or .icc since these are the standard file extenstions that
all software expects for profiles. Next use the "Edit Profile
Identification" button and fill the info fields if you want
(again, this is recommended). It is important to include unique information
in the "Description"
field of this dialog since this information is used by many
applications, including LProf, to list profiles for users. I
will use this sample to present another utility, the profile checker. Since the profile checker can understand advanced tags,
we want to include all information in the profile, so select the
"Edit Profile Parameters"
button, and make sure to select "Verbose, store anything" in the
"Profile verbosity" group. Next press then press the "Create Profile"
button. A
new profile will be created. We will check now how
accurate this profile is. Start the profile
checker dialog selecting the "Profile Checker"
button.
The profile checker is a tool for
inspecting some of profiles
internal data. In our case, we want to check the accuracy.
Create a Measurent File Outside of LProf
To do this you need to create a IT8/CGATS
measurement sheet file containing XYZ
measurements for several RGB combinations for your monitor. A
sample file of this kind can be found in <prefix>"/share/lprof/data/pics" directory. Where <prefix> is the installation location of LProf.
If you are running LProf from the build directory these files
will be located in the data/pics directory of the source code tree.
The
file is
called "sRGB.IT8" and it contains measurements for an ideal sRGB monitor. Use this file
as a template for creating your own monitor measurement sheet file. You
need
to
change the XYZ values to those read by your measurement device. Don't
put any Lab values, just RGB and XYZ values. Please keep the RGB values the
sRGB.IT8 has. Optionally, you can use more patches to assure consistent
color reproduction, but make sure to include at least the ones in
sRGB.IT8. In the <prefix>"/share/lprof/data/pics" directory you will also find
"display patches.tiff". This file contains color patches that
correspond to the values used in sRGB.IT8 and it can be used to measure
the these RGB values from your display. Note that a large number of
gray patches are needed. You can also add as many as you wish, with
more gray patches, you will get better linearization control curves.
You must specify at least 16 gray patches.
To create a profile select the "Use externally generated
files" radio button. This will allow you to select or enter file
names for both the Measurement Sheet and the Calibration Sheet.
Creating a Calibration Sheet by hand is well beyond the scope of
this documentation and requires some fairly complex computation that
will make this an impossible task for most users without the use of
specialized software such as LProf. Therefore please leave the
Calibration Sheet entry empty unless you can somehow create a
Calibration Sheet file. But the resulting profile will not contain any calibration data in the form of a VCGT. A
measurement file created using the process in the last paragraph can be
used to create a profile by selecting it as your Measurement Sheet and
following the steps in "Create the Profile" (above).
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