I am hearing “late January” and that Nikon might offer the speculative 36MP D800 both with and without an anti-aliasing (blur) filter.
I have a dislike for AA filters but there has been no choice in this matter for DSLRs, so this is exciting news (speculation) about the (speculative) 36MP Nikon D800.
What’s an anti-aliasing filter?
An anti-aliasing filter is a blur filter, present on every DSLR on the market today (the Leica M9/M9P has no AA filter, but it is not a DSLR. Ditto for most medium format cameras).
The ostensible goal of an anti-aliasing filter is to reduce or eliminate moiré. It is very effective at this, with the side effect of blurring the finest details, which is a particular issue in low contrast dark areas (in my experience). Moiré occurs when the frequency of fine detail is close to that of the sensor.
Excellent lenses are the worst case
Moiré is naturally worst with the best lenses, because they have high resolving power at high contrast, e.g. the world-class Leica S lenses.
An average lens will have few moiré issues on a 36MP DSLR, because it won’t provide a good enough image: it’s blurred from poor resolving power and/or low contrast, hence it’s delivering an image not much different than the sensor would see with an AA filter.
Thus, as the camera resolution increases (for any particular sensor size), the likelihood of moiré tends to decrease, not because of increased resolution per se (since there are always detail frequencies which can provoke it), but because the lens starts to act almost like an AA filter on its own— optical performance along with diffraction at wider apertures (more significant as pixel size decreases) cuts resolving power and contrast, effectively blurring the finest details, just like an AA filter.