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Nikon and AA filters (Aka “Low pass” filter)
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Mar 14, 2019 13:58:41   #
Rich1939 (a regular here)
 
When Nikon introduced the D800 36mp camera they also introduced the D800E. The "E" model did not have the AA filter. That must have shown Nikon that the filter wasn’t required with high pixel count sensors and when they announced the D810 it was without filter and no option for one.. That AA (anti-aliasing) filter was originally there to prevent moire’ problems. Nikon has continued using the AA filter on sensors up to 24MP until the D5 and D500 intros in 2016. These cameras are both ~20MP without an AA filter. I thought that maybe Nikon had come up with a way to overcome the moire’ problem with the processors in the D5 and D500 cameras. Then, when the Z6 (24MP) came out the filter was back. I’m confused!
Do any of the tech-oriented members here have any thoughts about this?

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Mar 14, 2019 14:19:48   #
jamesl
 
Rich1939 wrote:
When Nikon introduced the D800 36mp camera they also introduced the D800E. The "E" model did not have the AA filter. That must have shown Nikon that the filter wasn’t required with high pixel count sensors and when they announced the D810 it was without filter and no option for one.. That AA (anti-aliasing) filter was originally there to prevent moire’ problems. Nikon has continued using the AA filter on sensors up to 24MP until the D5 and D500 intros in 2016. These cameras are both ~20MP without an AA filter. I thought that maybe Nikon had come up with a way to overcome the moire’ problem with the processors in the D5 and D500 cameras. Then, when the Z6 (24MP) came out the filter was back. I’m confused!
Do any of the tech-oriented members here have any thoughts about this?
When Nikon introduced the D800 36mp camera they al... (show quote)


----------------------------
I believe that the Nikon D7100 and the Nikon D7200 both do not have the AA Filter and they are 24MP cameras. My understanding is that in the D800E the AA filter was still there but a second filter was added to counter the effects of the AA filter.

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Mar 14, 2019 14:24:56   #
Rich1939 (a regular here)
 
jamesl wrote:
----------------------------
I believe that the Nikon D7100 and the Nikon D7200 both do not have the AA Filter and they are 24MP cameras. My understanding is that in the D800E the AA filter was still there but a second filter was added to counter the effects of the AA filter.


I wasn't aware of those. But, for me that just adds to the mystery of when the filters are used.

It turns out that the D5500 doesn't use a filter either.

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Mar 14, 2019 14:52:27   #
cameraf4
 
I believe it turned out that moire’ problems in DSLRs showed up so rarely that camera makers decided it was an extra expense on their part. Nikon used to show moire pics when they first marketed the D800 but I heard that it wasnt easy for them to replicate. I may be wrong.

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Mar 14, 2019 17:13:19   #
bkyser
 
I'll add to the questions, why does it cost more for a camera model with no AA filter than one that has one? Seems that if they don't put it in, it would save a little expense?

Yes, I'm a Nikon guy, but have never figured out why they do what they do... I just take photos

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Mar 15, 2019 06:44:26   #
billnikon (a regular here)
 
Rich1939 wrote:
When Nikon introduced the D800 36mp camera they also introduced the D800E. The "E" model did not have the AA filter. That must have shown Nikon that the filter wasn’t required with high pixel count sensors and when they announced the D810 it was without filter and no option for one.. That AA (anti-aliasing) filter was originally there to prevent moire’ problems. Nikon has continued using the AA filter on sensors up to 24MP until the D5 and D500 intros in 2016. These cameras are both ~20MP without an AA filter. I thought that maybe Nikon had come up with a way to overcome the moire’ problem with the processors in the D5 and D500 cameras. Then, when the Z6 (24MP) came out the filter was back. I’m confused!
Do any of the tech-oriented members here have any thoughts about this?
When Nikon introduced the D800 36mp camera they al... (show quote)


The D5 does have a AA filter. The D500 does not.

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Mar 15, 2019 08:06:03   #
Architect1776 (a regular here)
 
Rich1939 wrote:
When Nikon introduced the D800 36mp camera they also introduced the D800E. The "E" model did not have the AA filter. That must have shown Nikon that the filter wasn’t required with high pixel count sensors and when they announced the D810 it was without filter and no option for one.. That AA (anti-aliasing) filter was originally there to prevent moire’ problems. Nikon has continued using the AA filter on sensors up to 24MP until the D5 and D500 intros in 2016. These cameras are both ~20MP without an AA filter. I thought that maybe Nikon had come up with a way to overcome the moire’ problem with the processors in the D5 and D500 cameras. Then, when the Z6 (24MP) came out the filter was back. I’m confused!
Do any of the tech-oriented members here have any thoughts about this?
When Nikon introduced the D800 36mp camera they al... (show quote)


They haven't figured out how to eliminate moire. There is the assumption most users will not know what it is or not care that they have it in the photo. Other pixel peepers will sacrifice a good overall photo without moire in favor of looking at the photo at 400% with slightly sharper pixels.
Additionally the quality of the lens comes into play. a lower performing lens also acts as the AA filter so eliminating the need for the filter. Finally it is a marketing stunt in many cases for those who will accept moire in photos.

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Mar 15, 2019 08:39:23   #
Rich1939 (a regular here)
 
Architect1776 wrote:
They haven't figured out how to eliminate moire. There is the assumption most users will not know what it is or not care that they have it in the photo. Other pixel peepers will sacrifice a good overall photo without moire in favor of looking at the photo at 400% with slightly sharper pixels.
Additionally the quality of the lens comes into play. a lower performing lens also acts as the AA filter so eliminating the need for the filter. Finally it is a marketing stunt in many cases for those who will accept moire in photos.
They haven't figured out how to eliminate moire. T... (show quote)


I'll disagree with you on the assumption thing, the D500 is aimed at the pro market.
The underlying question remains, why do some lower pixel count cameras have the filter while others do not.

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Mar 15, 2019 08:40:10   #
Rich1939 (a regular here)
 
billnikon wrote:
The D5 does have a AA filter. The D500 does not.


Thanx for pointing that out. I sit corrected

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Mar 15, 2019 08:50:10   #
aflundi
 
Architect1776 wrote:
They haven't figured out how to eliminate moire. There is the assumption most users will not know what it is or not care that they have it in the photo. Other pixel peepers will sacrifice a good overall photo without moire in favor of looking at the photo at 400% with slightly sharper pixels.
Additionally the quality of the lens comes into play. a lower performing lens also acts as the AA filter so eliminating the need for the filter. Finally it is a marketing stunt in many cases for those who will accept moire in photos.
They haven't figured out how to eliminate moire. T... (show quote)


Architect1776 is right. AA filters are a good thing, and if anything are too weak. The dual-layer birefringent type filters we commonly call Anti-Aliias filters would be more accurately called Color-Preservation filters as they guarantee that any detail is presented to each of a R, G, and B photosite and is thus recorded with the correct color. Without this filter, a white detail that images onto a blue photosite is recorded as a blue detail, not a white detail. Thus sensors without this filter have high color noise. There's also the problem that information can be completely lost. For example, a blue detail that images onto a red photosite is complete lost from the image.

For the filter to work properly as a true Anti-Alias filter, it would actually need to be four layers and cover a 4x4 photosite area so that two photosites with the same color fitler would be covered in any linear direction. That would eliminate moire.

The rationale for leaving these filters off of high pixel density sensors is the idea that the lens's image being imperfect could provide enough blur compared to the tiny photosites to perform the function of an AA filter. That has been shown to be a bad assumption as even lenses known for their softness still produce aliasing artifacts including moire. Worse, most lenses today are astonishingly sharp with aggravates the problem.

BTW, DX sensors are smaller so the photosite size is smaller for the same pixel count compared to a larger FX filter. That's why Nikon tried leaving the filter off the D500, D7100, D7200, and D7500. The D5, however, as already pointed out above does have the filter. It would be a disaster otherwise. It's also Nikon's flagship body, so cutting corners by leaving off critical components such as this color-preservation filter would be very unlikely.

Architect1776 is also correct that these filters are left off because people buy them, and not for technical reasons. No competent engineer would think this is OK. I'm quite sure the Nikon engineering department has been at great odds with the marketing department over these decisions.

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Mar 15, 2019 09:10:47   #
Architect1776 (a regular here)
 
Rich1939 wrote:
I'll disagree with you on the assumption thing, the D500 is aimed at the pro market.
The underlying question remains, why do some lower pixel count cameras have the filter while others do not.


Why does the Pro D5 have the filter?
Perhaps for maximum quality overall?

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Mar 15, 2019 09:30:52   #
JohnSwanda (a regular here)
 
I have a Nikon D7100 without the AA filter. I have had a few occasions of moire in fabrics. I have been able to fix it acceptably in post, but it is still a pain in the neck.

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Mar 15, 2019 10:09:46   #
Rich1939 (a regular here)
 
Architect1776 wrote:
Why does the Pro D5 have the filter?
Perhaps for maximum quality overall?


And the pro D500 doesn't? Is it that smaller pixel pitch can get away without it?
I might have just answered my own question.

Cameras with filter
Model_______Pixel pitch
D750_______ 5.8
D5_________6.45
Z6_________5.94

Without Filter

D810_______4.88
D500_______4.2
D7200______3.92
D7500______4.2
Z7_________4.35

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Mar 15, 2019 10:16:27   #
selmslie (a regular here)
 
Architect1776 wrote:
They haven't figured out how to eliminate moire. There is the assumption most users will not know what it is or not care that they have it in the photo. ...

Pretty much the story in a nutshell.

Moire in a digital image can occur when a repeating pattern in some man-made object (cloth, window screen, etc.) happens to coincide with the pattern in the camera's sensor. It almost never occurs in nature unless you are photographing feathers. Changing the subject distance slightly or zooming in or out can eliminate it.

A higher sensor resolution simply means that moire that was visible with a 200 count bed sheet might now show up at 300 count.
aflundi wrote:
.. AA filters are a good thing, and if anything are too weak. ...

If your choice of subject matter does not expose you to the possibility of seeing moire, the AA filter is definitely not a good thing. They reduce resolution throughout the image regardless of whether or not there is any potential for moire.

When moire actually appears it is usually confined to a small part of the image. It's a simple matter to treat only the affected part of the image while protecting the rest of the image from loss of sharpness with masking. The same procedure can be used to selectively reduce grain the portion of the image where it is objectionable without reducing the sharpness in the rest of the image.

Given a choice, would you not prefer your images to be sharp as possible? You can take steps to suppress moire or grain selectively during post processing.

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Mar 15, 2019 12:05:36   #
speters (a regular here)
 
Rich1939 wrote:
When Nikon introduced the D800 36mp camera they also introduced the D800E. The "E" model did not have the AA filter. That must have shown Nikon that the filter wasn’t required with high pixel count sensors and when they announced the D810 it was without filter and no option for one.. That AA (anti-aliasing) filter was originally there to prevent moire’ problems. Nikon has continued using the AA filter on sensors up to 24MP until the D5 and D500 intros in 2016. These cameras are both ~20MP without an AA filter. I thought that maybe Nikon had come up with a way to overcome the moire’ problem with the processors in the D5 and D500 cameras. Then, when the Z6 (24MP) came out the filter was back. I’m confused!
Do any of the tech-oriented members here have any thoughts about this?
When Nikon introduced the D800 36mp camera they al... (show quote)

It really has nothing to do with the amount of mega pixels in cameras, but it does just make more sense to leave it out with cameras that do have a somewhat high amount, so people can "squeak" out the last bit of detail out of their sensors!

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