When using motion blur, Blender uses steps, between which the motion is blurred.

These steps are distributed evenly over the whole motion blur range. This does not sound unintuitive at first, because most of the time, the motion blur range will be less than one frame, and the default of 1 step creates an additional step somewhere between frames.

But when the motion blur range is longer than one frame, maybe 60 frames, Blender still only uses one additional step in the whole 60 frame motion blur range. This looks very broken, because the visible motion, and the blur don't match. This happens in EEVEE and Cycles (but in Cycles there is no global option for steps).

Videos:

Something, that should look like this: projects.blender.org/attachments/f04f1373-658d-457a-b747-e07b96801e4a

Looks like this by default: projects.blender.org/attachments/414a4292-3fca-498e-abf1-f9c28fe46baf

Proposal:

Make the step system independent of the motion blur range length. The steps should define how many sub steps there are between frames, not how many steps there are in the whole motion blur range. This way, every frame in the motion blur range will have a step by default, with three additional steps between frames by default. If more steps are needed between frames, this can still be increased by adjusting a "sub step" slider.

This was originally a bug report: projects.blender.org/blender/blender/issues/107482