VD66GY + Rockchip RV1106 ISP – Green color cast and low saturation, need sensor tuning guidance

[satishkatti]

 

Hi ST team,

I am using the ST VD66GY image sensor connected to a Rockchip RV1106 processor with the Rockchip hardware ISP.

I have successfully enabled the camera pipeline and can capture images, but the image quality has a strong greenish color cast and the colors look desaturated, even under a bright indoor room with white LED lighting.

Current setup

• Sensor: ST VD66GY

• Processor: Rockchip RV1106

• ISP: Rockchip RKISP (hardware ISP)

• Capture: RAW from VD66GY → RKISP → Image output

Observed issue

• Strong green tint across the entire image

• Skin tones appear gray/green

• Low color saturation

• Indoor lighting is much brighter than what the captured image suggests

I have attached three sample images captured with the current ISP settings.

Questions

1. Does ST provide an IQ tuning file or reference tuning parameters for VD66GY when used with a third-party ISP such as Rockchip RKISP?

2. Are there recommended AWB calibration, Color Correction Matrix (CCM), or Lens Shading Correction (LSC) values for this sensor?

3. Is the green cast typically caused by missing sensor calibration data, or should it be corrected entirely through ISP tuning?

4. Is there any recommended register configuration for VD66GY that improves color reproduction before ISP processing?

Any guidance or reference tuning data would be greatly appreciated.

Thank you!

[prime5711]

I am also testing the VD66GY camera module,
and I find this issue puzzling.
Based on the "Embedded Functions" section of the VD66GY datasheet,
I had expected much better image quality than what I am seeing.

I am wondering if the cause of this issue is a missing configuration in the kernel device driver,
or if the image quality is simply poor even with proper settings—implying that an external ISP is required.

Additionally, I used the "STEVAL-CAM-M0I1" to test the VD66GY,
but because the MIPI signal polarity is reversed, a direct connection isn't possible, requiring the fabrication of an interface board.
- There seem to be very few boards with an RPI camera interface that support MIPI polarity reversal, and the process is cumbersome.

 

 

[michaeltang]

the MIPI signal polarity is reversed, a direct connection isn't possible

 

Hello prime5711,

There is an OIF_CTRL register that can be used to swap the MIPI clock lane and data lanes. Please refer to UM2602, section 16.1, “Configuration,” and the output interface configuration registers table for the detailed bit mapping.

[michaeltang]

Hello satishkatti,

Thank you for your interest in ST products and welcome to the ST community.

For your question,

1. We do not provide a tuning guide for third-party ISPs. This is generally outside the scope of the sensor vendor, so we suggest you contact the ISP vendor directly for Rockchip RKISP tuning support.

2. AWB, CCM, and LSC values are highly dependent on the specific camera module, including the sensor, lens, optical path, and ISP pipeline. Therefore, we do not provide generic calibration values for third-party ISP platforms. For reference only, you may check the tuning data available for some ST sensors in the Raspberry Pi libcamera repository, for example: libcamera/src/ipa/rpi/pisp/data/vd56g3.json at main · raspberrypi/libcamera

3. A strong greenish color cast is often related to ISP calibration, especially AWB and CCM tuning. If the RAW output from the sensor is correct, color reproduction is typically adjusted in the ISP rather than by the sensor itself.

4. There is no universal sensor register setting to tune color reproduction directly before ISP processing. However, basic sensor parameters such as black level / pedestal / dark calibration settings must be configured correctly, since an incorrect pedestal may affect the RAW baseline and indirectly impact AWB/CCM results. Color reproduction is still typically finalized in the ISP through calibration.

Best regards,

Michael