Path: utzoo!attcan!uunet!cs.utexas.edu!news-server.csri.toronto.edu!neat.cs.toronto.edu!mgreen
From: mgreen@cs.toronto.edu (Marc Green)
Newsgroups: comp.graphics
Subject: re: Motion blur
Message-ID: <90Aug6.110342edt.7596@neat.cs.toronto.edu>
Date: 6 Aug 90 15:03:57 GMT
Organization: Department of Computer Science, University of Toronto
Lines: 42

>From: ritter@versatc.versatec.COM (Jack Ritter)

>Are there sound physiological principles that support
>the need for motion blur? My eyes didnt seem to
>need it, at least not at the frame/sec rate he showed.

>Maybe there's another factor: We're so used to seeing
>motion blur all our lives, from film & tv cameras, that when
>you take it away, we MISS it.

I think I can answer your questions. First, the visual system has a
mechanism which suppresses blur. The persistence characteristics of
the retinal image should produce long streaks trailing any moving
object - but it doesn't. There is some sort of inhibitory mechanism
minimizing the streaking.

The reason that bluring images reduces motion aliasing is that it
removes high spatial frequency components from the image. The high
frequency components have longer persistence, so they create longer
trails and disrupt perception of smooth motion. There are numerous
papers on this, including some of mine, in the vision literature.

One last thing. This business about emulating a camera is a waste of
time. The real issue is how the make the images match the capabilities
of the visual system. Fixation with camera emulation gets in the way
and obscures the real issues. Your question is a perfect example.

>Well, I LIKED the stroboscopic one 
>BETTER than the motion blurred one.
>It was simply crisper and more enjoyable than the
>mushiness of the blurred version.

Your terminology is wrong.  Stroboscopic motion refers to any motion
creeated by a sequenve of still images. There are many types of
stroboscopic motion, which people seem to confuse. In particular
people (even some experts) confuse beta motion and phi motion. Beta
motion is stroboscopic motion which is indistinguishable from real
motion; phi motion is "disembodied motion, where you feel as if the
something moved, yet the images appear to flicker.

Marc Green
Trent University