Yep agreed, this is not a Moire effect, simply overlapped arcs of blurred
spoke.
- Peter
-----Original Message-----
From: Igor Roshchin
Sent: Sunday, December 26, 2010 9:52 AM
To: [email protected]
Subject: Re: The Physics of Photographing Moving Subjects
Sat Dec 25 11:26:39 CST 2010
Doug Franklin wrote:
I should note that a similar effect can be expected when the tire
> makes
> not about 1/15th of a turn, but also 2/15th, 3/15th, etc. (N/15),
> but the contrast will be lower, and it probably wouldn't work beyond
> N=3 (or maybe even 2, depending on the light conditions).
Yeah, that's part of the moire effect. Many integral
multiples/fractions will give related effects.
I don't think that it is exactly the moire effect, as there
are no true interference, and there are no different-angle grids.
Or, I should say, - this (as well as what Doug originally showed)
would be the most trivial version of it: overlap of several circular
(covering a solid arc) objects (the area covered by each spoke within
the shutter-open time) with the same offset from each other.
It is trivial in the fact that you are not gaining any new periodicity
of the pattern, as what usually is significant in moire.
Igor
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