(1) Original test image without noise. There is a large step in the middle, a bright thin line and a shading from the top left corner to the bottom right corner. (2) Original test image with a lot of noise. The step is barely visible, while it is impossible to see the line or the shading. (3) Resulting image after 2D denoising. The step is almost visible and it is possible to see that the top left corner is brighter than the bottom right corner. (4) Resulting image after 3D denoising. Now the step and the shading are clearly visible, but not the line. (5) Resulting image after 4D denoising. Now all parts of the image are clearly visible.
