Issues with Realsense d456 at close range

[AidenNeale]

We've recently started using a Realsense d456 depth camera with the hopes of mapping underground infrastructure. When running some experiments we visualised a lot of ghost points (points that were outside of the visible scene) from the depth pointcloud, as you can hopefully observe in the video below. Note the areas to the left and top of the video where the depth map alternates between black and bright white.

Screencast.from.2025-11-04.17-37-31.mp4

We've re-calibrated the depth camera in the Realsense-viewer application and have obtained values of 0.0 and 0.01, so the calibration seems reliable.

We retested in a corridor and are seeing similar results on the floor (where it would be beneath the minimum distance. Our assumption was that values below the minimum distance would just report 0m, however we're seeing values of > 2m in places where we would expect nothing.

corridor_depth_test.mp4

This only seems to happen when there are points within 0.5m. Is this expected behaviour for a realsense depth camera when something is below its minimum depth range?

We've also played around with the Gain and Exposure settings in the realsense-viewer but we've not had much luck.

Hopefully you'll be able to provide a fix if working unexpectedly or an explanation of why it works as expected.

Thanks

[MartyG-RealSense]

Hi @AidenNeale The depth measurements do not suddenly turn off to zero below the minimum distance. Instead, the depth becomes inaccurate as the image progressively breaks up and disappears to black the closer that the camera is moved towards the observed object / surface.

You can move the camera below 0.5 meters if you use a setting in the Viewer called Disparity Shift. As you increase the Disparity Shift above its default value of zero, the minimum distance of the camera reduces to allow the camera to get closer to the surface before the depth image starts breaking up. The trade-off is that the maximum observable distance reduces as Disparity Shift is increased. So if you require the background detail too, setting Disparity Shift between 50 and 100 is recommendable.

You can find the Disparity Shift setting in the Viewer under Stereo Module > Advanced Controls > Depth Table

In regard to your target application of underground infrastructure, the case about using a RealSense camera in an underground car park at #10229 may be a helpful reference.

[MartyG-RealSense]

Hi @AidenNeale Do you require further assistance with this case, please? Thanks!