Display Settings (Brightness, Contrast, etc.)

Several of Wacom's Cintiq displays use software rather than hardware controls to adjust brightness and contrast. Linux has a pair of utilities that may be used to change the settings depending on your distribution.

DDC Monitor Control

Prerequisites

Before running any of the commands below, you must first ensure the kernel's I2C driver has been loaded. This can be done temporarily by running sudo modprobe i2c-dev. Alternatively, the I2C driver can be automatically loaded whenever the system starts by adding i2c-dev to your system's module load file (one of /etc/modules, /etc/modules.conf, or file inside /etc/modules-load.d/). After loading the I2C driver, there should be one or more files named /dev/i2c-<n> that correspond to the various I2C devices connected to the system.

Using ddcutil

Follow the instructions at https://www.ddcutil.com/install/ to install the ddcutil tool. Packages are available for several distributions.

After installing, run sudo ddcutil dectect to ensure your Cintiq is visible. Next, you can use sudo ddcutil --mfg WAC capabilites to discover the settings that exist. You can run sudo ddcutil --mfg WAC getvcp <code> to see the current value of any setting or sudo ddcutil --mfg WAC setvcp <code> <value> to change its value. A sample session is below:

# Ensure the I2C driver is loaded or else ddcutil will not work
$ sudo modprobe i2c-dev

# Find attached monitors
$ sudo ddcutil detect
Invalid display
   I2C bus:             /dev/i2c-15
   EDID synopsis:
      Mfg id:           LEN
      Model:            Unspecified
      Serial number:    Unspecified
      Manufacture year: 2009
      EDID version:     1.3
   DDC communication failed

Display 1
   I2C bus:             /dev/i2c-17
   EDID synopsis:
      Mfg id:           WAC
      Model:            Cintiq 13HDT
      Serial number:    4LAHS00045
      Manufacture year: 2014
      EDID version:     1.3
   VCP version:         2.1

# Get the Cintiq's capabilities. If multiple displays were detected, you can
# specify specify which ddcutil works with by providing the display number ("-d"),
# manufacturer ("--mfg"), model name ("--model"), etc. See `man ddcutil` for details.
$ sudo ddcutil --mfg WAC capabilities
MCCS version: 2.1
Commands:
   Command: 01 (VCP Request)
   Command: 02 (VCP Response)
   Command: 03 (VCP Set)
   Command: 07 (Timing Request)
   Command: 0c (Save Settings)
   Command: e3 (Capabilities Reply)
   Command: f3 (Capabilities Request)
VCP Features:
   Feature: 02 (New control value)
   Feature: 04 (Restore factory defaults)
   Feature: 08 (Restore color defaults)
   Feature: 10 (Brightness)
   Feature: 12 (Contrast)
   Feature: 14 (Select color preset)
      Values:
         04: 5000 K
         05: 6500 K
         08: 9300 K
         0b: User 1
   Feature: 16 (Video gain: Red)
   Feature: 18 (Video gain: Green)
   Feature: 1A (Video gain: Blue)
   Feature: 52 (Active control)
   Feature: 6C (Video black level: Red)
   Feature: 6E (Video black level: Green)
   Feature: 70 (Video black level: Blue)
   Feature: 86 (Display Scaling)
      Values:
         03: Max vertical image, no aspect ratio distortion
         08: Linear expansion (compression) on h and v axes
   Feature: AC (Horizontal frequency)
   Feature: AE (Vertical frequency)
   Feature: B6 (Display technology type)
   Feature: C8 (Display controller type)
   Feature: DF (VCP Version)

# Get the brightness, contrast, and color preset
$ sudo ddcutil --mfg WAC getvcp 10
VCP code 0x10 (Brightness                    ): current value =    50, max value =   100
$ sudo ddcutil --mfg WAC getvcp 12
VCP code 0x12 (Contrast                      ): current value =    50, max value =   100
$ sudo ddcutil --mfg WAC getvcp 14
VCP code 0x14 (Select color preset           ): 6500 K (sl=0x05)

# Change the brightness to 25%, contrast to 75%, and color preset to 5000K
$ sudo ddcutil --mfg WAC setvcp 10 25
$ sudo ddcutil --mfg WAC setvcp 12 75
$ sudo ddcutil --mfg WAC setvcp 14 4

Using ddccontrol

The ddccontrol program is an alternative to ddcutil that may be available on older distributions. Please read the man page for usage instructions.

Adjusting in another OS

As a last resort, the display settings can usually be adjusted by temporarily connecting the Cintiq to a computer running Windows or macOS. The Wacom driver includes a "Wacom Display Settings" tool that can quickly adjust the monitor to your preferences. The values are stored on the device and will persist after returning to the Linux environment. Instructions on using "Wacom Display Settings" tool can be found here.

Other Settings

This is a list of other settings that might be useful to adjust:

Full-range RGB

The Intel graphics driver for Linux sends "limited range" (16-235) RGB values to HDMI displays by default. To prevent blacks from being crushed and whites from being blown out, you will want to run the following command to have it send the full 0-255 range of RGB values. Note that this preference will be reset if you restart the computer, and possibly even if you logout. If you are using a color-managed workflow, be sure this setting is the same when calibrating the display and viewing content.

$ xrandr --output "<OUTPUT>" --set "Broadcast RGB" "Full"

You can return to using limited range with the following command:

$ xrandr --output "<OUTPUT>" --set "Broadcast RGB" "Limited 16:235"