Hi everyone, I’m trying to get lens shading correction working on the USB3.0 Camera Shield Plus with an IMX219 sensor. I’ve been digging around and the only code I can find for lens shading correction goes through the Raspberry Pi interface. Does anyone know if there’s a way to apply lens shading correction through the USB3 shield directly from Python? I’d really appreciate any suggestions or sample code.
Thanks for reaching out. Can you share a bit more about your setup so I can point you in the right direction? Are you using the shield with a Raspberry Pi host, or on another machine? Also, how are you capturing frames right now in Python (OpenCV, V4L2, raw USB reads, etc.)?
Right now I’m running everything in Python. I have multiple USB3.0 Camera Shield Plus units with IMX219 cameras and I’m pulling frames from them over USB. I originally found the lens shading correction code through the Raspberry Pi interface examples, but I can’t figure out how to do the same thing through the USB3 shield path. I don’t really have any custom code for this yet because I’m not sure where to start.
Got it. Just to make sure I’m looking at the same thing you found: the Raspberry Pi interface path you mentioned goes through the CSI connection and the ISP pipeline on the Pi, which is where the lens shading correction is handled. The USB3.0 Camera Shield Plus is a different path though. Let me dig into how the shield exposes data and whether it has any LSC controls.
Yes, that’s exactly it. On the Pi interface path the shading correction is handled there, and the images look noticeably different when I compare them. Over USB I’m getting what looks like raw sensor output, and I can see the vignetting/shading in the corners that I’d normally correct with LSC. So I was hoping there was some control or library call through the USB3 shield in Python to enable the same correction.
I checked into this. The USB3.0 Camera Shield Plus is designed to output raw data directly from the IMX219 sensor over USB. There’s no on-board ISP on the shield that performs lens shading correction, and I don’t see any control or register interface exposed over USB that would let you enable LSC from Python. In other words, the shield just hands you the raw sensor stream.
Hmm, so does that mean there’s no way at all to get lens shading correction through the USB3.0 interface? Is there maybe a firmware flag or a command I can send to the shield?
Unfortunately, based on what I’ve found, lens shading correction is not available on the USB3.0 Camera Shield Plus itself. The shield outputs raw sensor data directly, and there is no code path or method provided by the shield to apply LSC through the USB3 interface from Python. That’s the key difference from the Raspberry Pi interface, where the correction exists because it’s done in the Pi’s ISP pipeline rather than on the camera hardware. So the capability you’re looking for isn’t supported on the shield’s USB path.