# The benefits of (non-perceived) flicker

By: SM (moeller0.delete@this.gmx.de), January 10, 2013 12:37 pm
Max (max.delete@this.a.com) on January 10, 2013 6:18 am wrote:
> Anon (no.delete@this.email.com) on January 9, 2013 9:50 pm wrote:
> > Max (max.delete@this.a.com) on January 7, 2013 6:16 pm wrote:
> > > Ungo (a.delete@this.b.c.d.e) on January 7, 2013 3:57 pm wrote:
> > > > Max (max.delete@this.a.com) on January 7, 2013 1:43 pm wrote:
> > > > > Oddly enough the flickering nature of CRTs (whether perceived or not) makes them inherently superior
> > > > > in displaying motion than modern panel displays. A moving image (updated at the display refresh
> > > > > rate) appears sharp, whereas on a non-flickering display it appears fuzzy. This would be true
> > > > > even if the panel can update instantly, so it's not a problem that will ever go away.
> > > >
> > > > The bolded statement is not true. The reason why moving objects on LCDs often look fuzzy is because
> > > > LCD pixels have poor response times. Take that away, and the fuzziness should go too.
> > >
> > > That's a big problem, but even an absolutely perfect panel would have worse motion than a CRT.
> > >
> > > Think about how you're able to perceive a moving image as sharp. It's because the
> > > eye moves with the image, so the image is stationary with respect to the eye.
> > >
> > > When viewing a panel, the tracked image is only correct momentarily
> > > every frame. The rest of the time the image
> > > is wrong, and this wrong image is averaged by the eye with the correct image to produce a blurry image.
> > >
> > > You can see this effect with a CRT: take a 60Hz source and convert to 120Hz by repeating
> > > frames. The 120Hz version will be less sharp! (For motion that the eye can track).
> > >
> > > Max
> > >
> >
> > Ah, no citations despite two polite requests other than more hand
> > waving, time to (not surprisingly) call BS on this one I suspect.
>
> google "motion blur" "eye tracking"

To visualize this, figure 1 in http://www.mpi-inf.mpg.de/resources/3DTemporalUpsampling/3DTemporalUpsampling.pdf has a quite nice illustration of hold-type blur caused by the interaction of an LCD display and visual tracking of moving objects. This also makes is clear why higher refresh (or more correct shorter hold times) can ameliorate this effect, at least with a higher real frame rate or interpolated frames in between, as the apparent step size decreases so does the magnitude of the "apparent" blur kernel (not fully correct, but close).

>
> > Also, you seem to completely misunderstand how we perceive motion, partially because you
> > think eyes track a moving item on a frame by frame basis (incorrect) and secondly because
> > of your absolutely crazy assertion that a frame doubled 60Hz sequence will be somehow less
> > sharp (hint: it is exactly the same as a 60Hz version on a persistent display).
>
> Hint: if something seems crazy, try reading more carefully. I said with a CRT, not with a persistent
> display. The CRT is physically refreshing at 120Hz, but the source is 60Hz (repeated frames).
>
> The repeated frames introduce motion blur, even though the
> CRT is completely free of LCD response time problems.
>
> The blur occurs because the eye is moving but the image is not. The object you are tracking
> looks "out of focus" because there's no way to stabilize the image at the eye.
>
> Max
>
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Oh, for crying out load, would you fix this stupid thing to make it a tiny bit harder to double post (NT)rwessel2013/01/03 12:01 PM
Oh, for crying out load, would you fix this stupid thing to make it a tiny bit harder to double postDavid Kanter2013/01/10 10:07 AM
Oh, for crying out load, would you fix this stupid thing to make it a tiny bit harder to double postrwessel2013/01/10 09:33 PM
Oh, for crying out load, would you fix this stupid thing to make it a tiny bit harder to double postrwessel2013/01/10 09:35 PM
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