AA filter vs. OLPF filter

[Brianm]

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?

[Floyd L. Davidson]

Post by Brianm
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?

Every AA filter is necessarily an OLPF. Not every OLPF works in the
range needed to be effective as an AA.

[nospam]

Post by Brianm
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.

[nospam]

Post by nospam

Post by Brianm
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.

[Floyd L. Davidson]

Post by nospam

Post by nospam

Post by Brianm
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?

[nospam]

Post by Floyd L. Davidson

Post by nospam

Post by nospam

Post by Brianm
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/Images/Learn-Explore/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.

[Floyd L. Davidson]

Post by nospam

Post by Floyd L. Davidson

Post by nospam

Post by nospam

Post by Brianm
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.

It's name is not, and never has been, "un-alias" anything.

Nothing in any of your cites suggests that is correct
terminology, and it isn't. It does suggest a total lack
of understanding about what the filter does. It is an
*anti* aliasing filter because it helps to stop
aliasing. There is no filter that *un*-aliases
anything.

[nospam]

Post by Floyd L. Davidson

Post by nospam

Post by Floyd L. Davidson

Post by nospam

Post by nospam

Post by Brianm
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.

It's name is not, and never has been, "un-alias" anything.

it has, and is.

Post by Floyd L. Davidson
Nothing in any of your cites suggests that is correct
terminology, and it isn't. It does suggest a total lack
of understanding about what the filter does. It is an
*anti* aliasing filter because it helps to stop
aliasing. There is no filter that *un*-aliases
anything.

in the d800e, the second filter reverses the anti-aliasing of the first
filter, thus the 'un-' prefix.

in the d800, the second filter is another anti-alias filter in the d800
for the second dimension.

this is *clearly* spelled out in nikon's documentation and elsewhere.
if anyone lacks an understanding about how it works, it's you.

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

go tell nikon they're wrong. let us know how well that works out.

[Floyd L. Davidson]

Post by nospam

Post by Floyd L. Davidson

Post by nospam

Post by Floyd L. Davidson

Post by nospam

Post by nospam

Post by Brianm
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.

It's name is not, and never has been, "un-alias" anything.

it has, and is.

Making up your own set of facts doesn't make your
argument correct. Not one of your cited references
uses that term!

Post by nospam

Post by Floyd L. Davidson
Nothing in any of your cites suggests that is correct
terminology, and it isn't. It does suggest a total lack
of understanding about what the filter does. It is an
*anti* aliasing filter because it helps to stop
aliasing. There is no filter that *un*-aliases
anything.

in the d800e, the second filter reverses the anti-aliasing of the first
filter, thus the 'un-' prefix.

That suggests you haven't got a clue how an OLPF works.
There is no "anti-aliasing" in the filter. The filter
is a pair of layers of birefringent material aligned
such that together they slightly blur the image. That
reduces aliasing when the image is sampled by the sensor.

All that happens in the D800E is that those two layers
are not aligned to blur the image.

Post by nospam
in the d800, the second filter is another anti-alias filter in the d800
for the second dimension.

The "second filter" is second layer of birefringent
material oriented at 90 degrees to the first. In the
D800E it is oriented at 180 degrees.

Post by nospam
this is *clearly* spelled out in nikon's documentation and elsewhere.
if anyone lacks an understanding about how it works, it's you.
<https://www.nikonusa.com/en_INC/IMG/Images/Learn-Explore/Camera-Technol
ogy/D-SLR/2012/Moire-D800-D800E/Media/OLPF_schematic.pdf>
go tell nikon they're wrong. let us know how well that works out.

The Nikon document does not use the term "un-alias". In
fact it does not even mention aliasing in any way. It
talks about how an Optical Low Pass Filter works, and
that does not directly involve aliasing, anti-aliasing,
or your ridiculous term "un-aliasing".