[mrob]

>Motion blur happens with real vision, so anything without blur would look odd.

You watch the video with your eyes so it's not possible to get "odd"-looking lack of blur. There's no need to add extra motion blur on top of the naturally occurring blur.

[erincandescent]

On the contrary, an object moving across your field of vision will produce a level of motion blur in your eyes. The same object recorded at 24fps and then projected or displayed in front of your eyes will produce a different level of motion blur, because the object is no longer moving continuously across your vision but instead moving in discrete steps. The exact character of this motion blur can be influenced by controlling what fraction of that 1/24th of a second the image is exposed for (vs. having the screen black)

The most natural level of motion blur for a moving picture to exhibit is not that traditionally exhibited by 24fps film, but it is equally not none (unless your motion picture is recorded at such high frame rate that it substantially exceeds the reaction time of your eyes, which is rather infeasible)

[the_af]

In principle, I agree.

In practice, I think the kind of blur that happens when you're looking at a physical object vs an object projected on a crisp, lit screen, with postprocessing/color grading/light meant for the screen, is different. I'm also not sure whatever is captured by a camera looks the same in motion than what you see with your eyes; in effect even the best camera is always introducing a distortion, so it has to be corrected somehow. The camera is "faking" movement, it's just that it's more convincing than a simple cartoon as a sequence of static drawings. (Note I'm speaking from intuition, I'm not making a formal claim!).

That's why (IMO) you don't need "motion blur" effects for live theater, but you do for cinema and TV shows: real physical objects and people vs whatever exists on a flat surface that emits light.

[estebank]

You're forgetting about the shutter angle. A large shutter angle will have a lot of motion blur and feel fluid even at a low frame rate, while a small shutter angle will make movement feel stilted but every frame will be fully legible, very useful for caothic scenes. Saving private Ryan, for example, used a small shutter angle. And until digital, you were restricted to a shutter angle of 180, which meant that very fast moving elements would still jump from frame to frame in between exposures.