This is a nice raw to shed some light on pixelshift and why it fails here when using plain pixelshift combine.
Let’s have a look at the 4 frames. There’s not much motion, but the light is changing.
Top left (1), bottom left (2), top right (3), bottom right (4), all demosaiced using amaze
As you can see, there’s
- the buoy in first frame, but not in the other frames
- the light on the right side of the building changes greatly
While a plain pixelshift combination greatly reduces the noise, it also gives some artifacts on the building as you can see here (left is amaze demosaic from first frame, right is pixelshift combined 4 frames without motion correction)
Even the motion correction can’t do much on this dark high ISO shot. Maybe there is some room for improvements, but it was designed for low ISO, where details are not (or less) affected by noise.
Fortunately, there is the median option, which also greatly reduces the noise. It has some donwsides (you may not want to use it if you have large movements in the scene, as moving foliage), but in this case, where we have changing light, and the movements are mostly on the water it works just fine.