Same thing goes for the feathers of a bird. Each barb is a wave crest, and the space between them is a trough. Overlay multiple feathers on top of each other, and you have a complex moire pattern.
And this very often is responsible for the various colors we perceive the feathers to be...but sometimes also the feathers have pigment...and sometimes it's both...correct?
Color would be different. I'm not talking about light waves, I'm talking about spatial waves. Color is determined by the ratio of energy absorption vs. energy reflection at the photon-electron interaction level in an atom. An object is red because it absorbs more of all other frequencies except red, and reflects more red than all other frequencies. ALL frequencies are absorbed, and ALL frequencies are reflected, the color of an object is ultimately determined by the amount of the spectrum reflected vs. not. A white object reflects all frequencies equally and absorbs all of them minimally, a black object also reflects all frequencies equally yet absorbs all of them significantly. This is also why darker objects tend to get hotter faster in the presence of electromagnetic energy, where as lighter objects get hotter slower.
Anyway, color is the result of an entirely different phenomena. When I say wave, I mean spatial frequency, not light wave.
But color in feathers is often determined by refracted light, not directly reflected light. Sorry you were not discussing color, in any case, but either way, this is what causes us to see various colors of feathers.
Yes, LIGHT is what determines color. But I am not talking about light. I'm talking about spatial frequencies. Spatial frequencies have nothing to do with light. Spatial frequencies are waves (two dimensional waves, to be precise), but not light.
Reflection, refraction, absorption...that is all a phenomena of photon-electron interaction at the atomic level. You can also include diffraction in that list as well...in some cases, some of the color patterns produced by bird feathers when illuminated by more direct light is the result of diffraction, as well as refraction and reflection. But again...that's light. I'm not talking about light, though. I am simply talking about shape and form and how those things can interfere...spatial structure.
How did you arrive at something so basic, from a discussion of AA filters? The nature of "resolution" has nothing to do with "spatial structure", because "detail resolution" exists on a much smaller scale...unless of course you're talking about cropping an image down to a few pixels square.
Sorry, not really sure what your asking here. This discussion ultimately came out of an earlier discussion about moire, and the cause of moire in photography is interference of spatial frequencies. I posted some bird photos on the demand of another member, and he noted seeing moire in them...however that moire was the result of bird feathers creating an interference pattern, not the sensor, and thus, the discussion at hand...about how moire can exist in reality without cameras at all, because it's all about spatial frequencies and how they interfere with each other.
I mean, what is the answer to this thread's question, in your mind? Will Canon ditch the AA filter completely, yes or no? If so, when?
No, I don't think Canon will ditch the AA filter at all. In all honesty, I find it ironic that the lack of an AA filter is considered a "high end" or "desirable" feature, just because Leica ditched them years ago (as did some MF cameras) and because now the schizophrenic Nikon has latched themselves and their success onto the removal of AA filters. It is even more ironic that those very same medium format cameras are frequently used to photograph people in studios, where fabrics of every variety are endemic. I have also read more than enough forum threads where MF users, including Leica users, complain about not having an AA filter because it produces so much moire.
Removal of an AA filter is far from a high end feature. It is a gimmick for all but a very few niche photographer types who's work primarily involves photographing things with entirely random data that could not produce much aliasing regardless. For the vast majority of photographers, use of an AA filter is quite essential to producing BETTER image quality. Aliasing produces nonsense, noise, useless detail. ANTI-Aliasing restores that useless nonsense noise to a more accurate form.
From a technical standpoint, an optical low pass filter is quite literally the best way to achieve this as well. X-Trans is a great example of this. While X-Trans doesn't experience aliasing, I've never seen any full size image that looked anywhere as sharp as the average full size DSLR image. X-Trans does basically the same thing as an optical low pass filter, however it is LESS discerning. A low pass filter is quite discerning in that it is designed only to blur certain spatial frequencies. Explicitly, optical low pass filters blur frequencies right in the range of the sensor's nyquist limit, the barrier between spatial frequencies that can be fully resolved without detrimental aliasing, and spatial frequencies that cannot be resolved properly at all, and are guaranteed to produce tons of nonsensical output that just increases noise. OLPFs blur exactly the right amount of high frequency detail so as to produce the least amount of impact on the photograph at large. There are some variations...some AA filters are slightly "strong" in that they blur a little bit of resolvable frequencies, other AA filters are a little "weak" in that they don't blur enough, resulting in some moire and aliasing occuring anyway. The X-Trans will blur all detail up to whatever radii is involved in their 6x6 grid overlap (which is pretty much guaranteed to be a larger radius than a low pass filter), so X-Trans will be blurring a lot more detail on a much more consistent basis.
It should also be noted that the kind of high frequency softening performed by an OLPF is easy to reverse. They produce a generally predictable form of blurring in a uniform manner across the entire area of the frame. As such, the application of a light unsharp mask filter can easily reverse the apparent softening, and restore the vast majority of "lost" detail (it's not really lost, most of it is there, especially if the AA filter isn't too strong.) Moire, on the other hand, is unpredictable, and can be extremely difficult to impossible to correct in post.
This, as it so happens, is also the case with lens diffraction. Many people mistakenly opt for using a wider aperture to avoid diffraction when what they really need is a deep DOF, however it is FAR more difficult to correct a depth of field that isn't deep enough. Diffraction blur is uniform across the entire area of the frame, and is predictable, and as such, it is easy to reverse with some sharpening. It is better to stop down more and deal with diffraction, than shoot wider and deal with a non-linear blur throughout the depth of field.
You gotta pick your battles, and it's best to pick the ones you can win. Combating softening due to an AA filter is easy. Super easy! The only people who complain about having an AA filter are those who don't quite understand it, how it works, or why we use them instead of some other alternative. Were more than a decade into the age of digital photography. It isn't like other options haven't been explored. Modern AA filters employ the best technique based on very sound theory, and are quite effective at the task. Removal of moire via post-processing tools? That is an area that has very little theory at all, has minimally effective tools at best, is impossible to correct at worst, and assuming there is a solution out there somewhere, will likely require many years or decades yet to discover a solution, effectively describe the process, and for some software developer to figure out how to convert the theory into an effective algorithm with a useful set of UI tools.
Personally, I hope Canon doesn't change a thing about their AA filters. IMO, they are already generally on the "slightly weak" side, and already allow too much moire through. I find the 7D AA filter to be quite effective at combating moire, and it is easy to sharpen the results to look as good as the competitors that don't have AA filters. I'm reposting an image from an old debate with Mikael on this very same subject, where I made the same arguments:
To the left is a 7D image taken from DPR, compared to one of Nikon's new AA-less cameras (D5100 or D7100, I forget which). I've applied a very light unsharp masking filter to the 7D to combat the softening caused by the AA filter. You will be very hard pressed to find any significant differences between these two images, with the exception that the image WITHOUT the AA filter clearly has problems with moire, where as the 7D does not. There is very little if any difference in sharpness, but the IQ of the 7D is higher...it's more accurate (and, it's also slightly over-exposed relative to the Nikon sample...I left that uncorrected, but that's why some of the fine detail doesn't look as "crisp"...it simply isn't as dark.)