Symptom

Computers and monitors equipped with hybrid cameras may show a color tint when used under certain lighting conditions. Not all materials are affected equally by this tint so different parts of an image such as a user’s hair or clothes may be tinted differently from their skin or background objects behind them.

Figure 1: A ceiling fan in true color vs. hybrid camera purple tint

Applicable Brands

ThinkPad

Applicable Systems

• L390
• L390 Yoga
• L490
• L590
• T490
• T490s
• T590
• T590s
• X1 Carbon 7th Gen
• X1 Yoga 4th Gen

System Is Configured With

RGB/IR hybrid camera

Operating Systems

Windows 10

Limitations

This purple tinting is an industry limitation of hybrid RGB/IR cameras. See Solution for ways to improve environmental light conditions, Workaround for camera tuning, and Additional Details for more information on why this tinting occurs.

Solution

IR tinting is caused by overloading the camera’s ability to color correct and can be prevented in two ways:

Reducing environmental IR light sources

Common IR sources to avoid are:

• Sunlight at sunset
• Sunlight at sunrise
• Firelight
• High-IR light bulbs:
  Tungsten filament (Incandescent)
  Halogen
  Xenon and Mercury-Xenon

Replacing incandescent fixtures and other high IR light bulbs with low IR bulbs such as LEDs or fluorescents will reduce artificial IR sources, while natural IR sources can be avoided with solutions such as closing curtains and using indoor lights at dawn and dusk.

Common low-IR light bulb alternatives:

• LED
• Fluorescent
• Compact fluorescent (CFL)

Filtering existing IR light sources

Existing light sources can also be filtered to block their IR light component while allowing visible light to pass through. This is done using IR-reflective window films and light bulbs that have IR-reflecting coatings such as IR Halogens.

Workaround

For situations where a hybrid camera is needed but IR light cannot be improved, it may be helpful to retune the camera's automatic white balance (AWB) to correct the resulting image tinting. This can be performed using this AWB RGB Gain Control Application available here: https://download.lenovo.com/km/media/attachment/AWBRGBGainCtrl_v1.17.zip

This application requires a camera driver update in order to control the system white balance, which can be found on the eSupport downloads page for your product as well as through other update tools such as Lenovo Vantage. This version can be identified by the readme contents (for example the X1 Yoga 4th Gen readme for 10.0.19041.20180/10.13.19041.13).

[New functions or enhancements]
 - Update Realtek driver to latest version with AWBRGBGainCtrl tool support.

Once the camera driver is installed, AWBRGBGainCtrl can be used in the following ways:

1. Run the AWBRGBGainCtrl.exe application.
   • This will automatically add a scheduled task to Windows so the application loads on start-up. Afterwards the application GUI will load.
2. Run AWBRGBGainCtrl.exe -auto
   • This will load the application minimized into the system tray without creating a scheduled task. This is recommended for users who want manual launch control.
3. Camera tuning by GUI
   • The AWBRGBGainCtrl GUI allows switching between 2 preset modes (default and incandescent light) as well as a third custom mode. By using the Expand button, sliders can be accessed to modify the Incandescent and Custom modes to better match your environment lighting. By default Incandescent mode is loaded on start-up. This can be modified by editing the AWBRGBGainCtrl.ini file.
4. Camera tuning by system tray
   • AWBRGBGainCtrl runs as a system tray icon when minimized and this is the default mode used by the Scheduled Task (see #1) and -auto start (see #2). As a system tray icon the GUI application can be launched, the mode can be quickly changed, or the application exited entirely.

The AWB RGB Gain Control Application system tray icon and right-click menu

Additional Information

What are Hybrid Cameras?

Most traditional webcams are RGB cameras, which means they detect light as a combination of red, green, and blue pixels. Some other camera products such as security cameras and night vision devices may instead use infrared cameras, which detect lower frequency infrared (IR) light that is invisible to the human eye.

Windows Hello requires an IR camera in order to properly detect a user’s face under varied conditions of lighting, make-up, etc. More information about Windows Hello and how it uses IR imaging is available at the following URL: https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/windows-hello-face-authentication

Figure 2: Camera images taken in RGB (left) and IR (right). IR images are more consistent across different lighting conditions.

To provide these features together, RGB imaging for traditional camera use and IR imaging for facial recognition, "hybrid cameras" combine light sensors from both camera technologies into a single device – that is, they are a hybrid of RGB and infrared cameras.

Figure 3: An RGB camera (left) with red, green, and blue sub-pixels compared to a hybrid camera (right) with IR sub-pixel added.

Why IR Causes Tinting

Because IR and RGB sensors are combined into a single camera, IR light can be detected by the RGB pixels, and when this happens a wrong color or "tint" is created. Camera algorithms will normally correct this color shift; however, under conditions with high IR light, some tint will be left over, creating an incorrectly colored image.

Depending on the design of the camera and color correction this tint can appear in different colors and patterns, but is most commonly purple or green.

Figure 4: IR tinting leftover from different color correction algorithms

How to Identify Hybrid Cameras

A hybrid camera can be identified using two methods together: system devices in Windows’ Device Manager menu and visual inspection of the device’s cameras.

In Device Manager, RGB camera products will only have an Integrated Camera or similar device under the Cameras category and no Integrated IR Camera will be present. Hybrid cameras show both Integrated Camera and Integrated IR Camera devices under the Cameras category. Some products may have separate cameras, one IR and one RGB. These may also show both camera devices in Device Manager. To distinguish this design form hybrid cameras, visual inspection of the cameras is required.

Visually, hybrid camera products have 1 camera lens and 1 IR LED (2 holes total). RGB+IR multi-camera products have 2 camera lenses and 2 IR LEDs (4 holes total). RGB camera products have 1 camera lens and no IR LEDs (1 hole total).

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