I would certainly agree that when someone says they see something, its hardly productive to argue the point.
I can refute the papers results, mostly because its incomplete. For one thing, it ignores the angular dependency that results from this apodization. A simple cross section of the point spread function does not demonstrate this. In fact the apodized spider creates 4 peaks in the first diffraction ring more evident than a normal spider yields. I don't know what kind of spider they compared against, they say a wire spider. A wire spider does almost nothing to the contrast transfer of the optic. Secondly they do not examine the imaging properties in detail, which would show the contrast being knocked down ~2.5% across the first 2/3 of the spatial frequency axis. This is not a trivial obscuration being added. Its consequence is not earth shattering but it does not seem called for, unless you really truly hate diffraction spikes. Finally they sort of dodge around the extra energy released about the central diffraction spot.
I cannot explain your results. However one can have certain aberrations, along with defocus and in various combinations that will result in perceived contrast features, primarilly in the higher spatial frequencies. But most of that percieved contrast results in false detections, and in fact contrast reversals. This can and does happen. Additional obscurations can amplify these effects. To be clear I am not saying this is your observation.
My analysis assumed perfect optics. I can add effects of various perturbations but don't see what that would tell me that is not already known, explained in the preceding paragraph.
This is not 'theory' using the common parlance definition - that is something proposed but not proven. Its the prediction of diffraction physics as we understand it going back at least one hundred years, which is proven.
I know this apodization reduces the extent of the diffraction spikes. There is no doubt about that. But it does not and cannot improve the imaging characteristics of an optic unless it is covering some flaw in the optic.
The objective here is only to inform. I am an experimentalist, as you are apparently. Keep it up! I enjoy trying different things as well. And I did say the paper was interesting.
Edited by DesertRat, 30 March 2015 - 07:04 PM.