In article , Floyd L. Davidson
wrote:

I'm confused by something. Many new cameras today advertise no
anti-aliasing filter (AA) or optical low-pass filter (OLPF). But are
they the same thing?? I came across one article that seems to say no,
saying (IIRC) the Nikon D810 has neither. However, I wonder if some
articles that say a certain camera doesn't have one or the other are
maybe using the terms interchangeably. Is it possible if a camera does
not have an AA filter it still has the OLPF, or vice versa? What's the
scoop?

two names for the same thing.

note that the d800 had an anti-alias filter for one direction and what
nikon called an un-alias filter so that the optical path was the same,
letting nikon produce the d800 and d800e without major differences.

make that the d800e with the un-alias filter. the d800 had an
anti-alias filter for both directions.

"Un-alias" filter?

yes. in the d800e, the second filter reverses the effect of the
anti-alias filter, thus its name.

http://imaging.nikon.com/lineup/dslr/d800/features01.htm

https://www.nikonusa.com/en_INC/IMG/...Camera-Technol
ogy/D-SLR/2012/Moire-D800-D800E/Media/OLPF_schematic.pdf

With the D800E, the effects of the low-pass filter is removed, and
the light is received by the image sensor at a single point,
achieving higher-resolution images with minimal blur.

http://www.dpreview.com/reviews/nikon-d800-d800e/3
Nikon uses slightly curious wording about the D800E - that the
anti-aliasing effect of the optical filter stack in front of the
sensor is 'cancelled' - and the diagram below shows what this means
(courtesy of Nikon). Anti-aliasing filters work by using a
birefringent material to split light rays into two based upon the
polarization of the light; a first layer splits it horizontally, the
second vertically. The practical result is a slight blurring of the
image, to avoid moiré and aliasing artefacts. In the case of the
D800E, the first filter is instead directly counteracted by the
second, resulting in no overall blurring.