Hi Joe, thanks for the response.
Daniel why is the frequency of the moire in the non AA image on the rivets for the diagonal beam low?
If you're saying that you see little or no aliasing (moire) of the rivets on the diagonal beam of the non AA image, then I disagree; to me it is aliasing there as well.
If you're asking why the spatial frequency at which the aliasing of the rivets occurs is so low, I would say that it's actually not very low at all -- in fact it's quite close to Nyquist. Really bad moire occurs at much lower spatial frequencies.
if indeed each rivet is represented by more than one pixel why are some rivets missing, unless of course, these rivets are not bright chrome but colored and/or missing.
Because when you practice unsafe imaging (without a protective AA filter), you contract certain artifacts: whether or not you see the rivet depends on chance alignment of the pixel grid.
Is it not a possibility that the AA filter reconstructed missing rivets from surrounding pixels by averaging;
No. The Bayer demosaic algorithm does use a dozen or more of the surrounding pixels to interpolate color values, but that occurs at a much higher level of detail than what you're seeing in this image. Remember that this is only 4 MP -- the original is 15 MP.
are all the rivets exactly uniform?
Download the original 15 MP raw file if you want to see what they really look like.