About AA filters

[aflundi]

I'm not sure if Pentax are alone in having AA filter simulation .

In their implementation , the camera has no AA filter in front of the sensor , but instead can use microscopic movement of the sensor , made possible by the anti-shake sensor movement facility , to achieve the same effect .

The beauty of this is that it can be turned on or off , and even implemented at different strengths .

Other makes will catch up ... eventually .

Does that work at fast shutters speeds?

 

[Pontoneer]

I'm not sure if Pentax are alone in having AA filter simulation .

In their implementation , the camera has no AA filter in front of the sensor , but instead can use microscopic movement of the sensor , made possible by the anti-shake sensor movement facility , to achieve the same effect .

Aliasing is still possible with the Pentax system (and one of the newer Micro 4/3rds cameras has it also?) but what it completely eliminates is color aliasing, which is a great benefit.

Basically, most cameras have different color filters at different pixel locations, and this offset can mean color artifacts even with purely monochrome subjects. A common fix for this is blurring the chroma, but you lose color detail, and it can be pretty obvious upon close inspection. The Pentax sensor shift system eliminates these color artifacts, but certainly you can still get moiré patterns and other aliasing.

A big problem with traditional antialias filters is that they aren't strong enough to eliminate color aliasing, and if they did, they would harm the resolution of the camera.

 

[Pontoneer]

I'm not sure if Pentax are alone in having AA filter simulation .

In their implementation , the camera has no AA filter in front of the sensor , but instead can use microscopic movement of the sensor , made possible by the anti-shake sensor movement facility , to achieve the same effect .

The beauty of this is that it can be turned on or off , and even implemented at different strengths .

Other makes will catch up ... eventually .

Does that work at fast shutters speeds?

In all honesty , I don’t know .

All I can tell you is that the menu setting is completely separate from shutter speed selection, but I can imagine that at shorter shutter speeds there would be less time for it to work . The vibration may be hypersonic though .

 

[aflundi]

Can someone explain to me why a camera having NO AA filter is a good thing. If I understand correctly, NOT having it can make for sharper photos. But if that's the case, why is it still there on certain cameras?

Marketing departments see that cameras without AA filters sell better. Companies can only survive if they can sell their products.

From a technical side though, it's insane to drop the AA filters.

The customers see something at the pixel-level that is more strongly emphasized without the AA filter and *think* they are getting more sharpness, when in fact that is an artifact. They also are missing that for every apparent sharp detail they see, they lose two equivalent details -- irretrievably. (A blue detail that images on a blue sensel is over emphasized, and a blue detail that images onto a red sensel or onto a green sensel is lost forever and cannot *ever* be recovered. This, and the need for AA-filters is very well understood in the signal processing world.)

AA filters preserve information at that detail level by directing the information to sensels that can record it.

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting. When the D850 was announced I was tempting to (try to) purchase one, especially because Nikon had added a number of features I had suggested to them back in 2015, but I ended up instead buying a used D800 *because* it has an AA filter. The D800's AA filter is too weak so with sharp lenses I still get AA artifacts, but the artifacts are weaker than those from the D810. And, with the 50mm/1.4{d or g} wide open on the D800, I get a very nice and smooth transition without AA artifacts at the pixel level. (Unfortunately, ugly artifacts return after stopping those "soft" lenses down just a bit. :-( )

Personally, I'd prefer to go the other way. I'd choose a camera with a full-strength AA-filter over an AA-less, or partial strength AA filter.

 

[aflundi]

Does that work at fast shutters speeds?

In all honesty , I don’t know .

All I can tell you is that the menu setting is completely separate from shutter speed selection, but I can imagine that at shorter shutter speeds there would be less time for it to work . The vibration may be hypersonic though .

The K-1 manual says it only works up to 1/1000th second.

 

[Mr Garibaldi]

I'm not sure if Pentax are alone in having AA filter simulation .

In their implementation , the camera has no AA filter in front of the sensor , but instead can use microscopic movement of the sensor , made possible by the anti-shake sensor movement facility , to achieve the same effect .

The beauty of this is that it can be turned on or off , and even implemented at different strengths .

Other makes will catch up ... eventually .

Does that work at fast shutters speeds?

In all honesty , I don’t know .

All I can tell you is that the menu setting is completely separate from shutter speed selection, but I can imagine that at shorter shutter speeds there would be less time for it to work . The vibration may be hypersonic though .

On the K1, Pentax says it’s good to 1/1000 second. The effectiveness drops off after that. It doesn’t Just stop working.

--
With kind regards
Derek.

 

[Mr Garibaldi]

Does that work at fast shutters speeds?

In all honesty , I don’t know .

All I can tell you is that the menu setting is completely separate from shutter speed selection, but I can imagine that at shorter shutter speeds there would be less time for it to work . The vibration may be hypersonic though .

The K-1 manual says it only works up to 1/1000th second.

It works past that, but it loses some effectiveness. In practice, it’s not much of a limitation.

 

[coudet]

The anti-aliasing filter is there to stop aliasing. Aliasing is a phenomenon that occurs when there is captured detail finer than the pixel array can deal with. What happens is that this incomplete data can interact to produce patterns in the photo that aren't there in the real image. The most obvious one is 'Moire', which is bands or ring patterns in the image, and is particularly visible when it interacts with the colour filter array to produce coloured bands. However, 'Moire' is not the only form of aliasing, you also get 'jaggies', step in lines that should be smooth, and often subtle changes in texture, sand that looks like lawn, velvet that looks like grit, etc.

However, an aliased image can look subjectively sharper, and this has become a fashion to which some camera manufacturers pander.

I knew we're in trouble when Leica M9 came out without a filter. It had unreal aliasing and every review looked at all that ugly aliasing... and praised the camera for it's outstanding "detail and per pixel sharpness".

 

[fishy wishy]

Can someone explain to me why a camera having NO AA filter is a good thing. If I understand correctly, NOT having it can make for sharper photos. But if that's the case, why is it still there on certain cameras?

The anti-aliasing filter is there to stop aliasing. Aliasing is a phenomenon that occurs when there is captured detail finer than the pixel array can deal with. What happens is that this incomplete data can interact to produce patterns in the photo that aren't there in the real image. The most obvious one is 'Moire', which is bands or ring patterns in the image, and is particularly visible when it interacts with the colour filter array to produce coloured bands. However, 'Moire' is not the only form of aliasing, you also get 'jaggies', step in lines that should be smooth, and often subtle changes in texture, sand that looks like lawn, velvet that looks like grit, etc.

However, an aliased image can look subjectively sharper, and this has become a fashion to which some camera manufacturers pander.

 

[Ian Stuart Forsyth]

Can someone explain to me why a camera having NO AA filter is a good thing. If I understand correctly, NOT having it can make for sharper photos. But if that's the case, why is it still there on certain cameras?

Marketing departments see that cameras without AA filters sell better. Companies can only survive if they can sell their products.

From a technical side though, it's insane to drop the AA filters.

The customers see something at the pixel-level that is more strongly emphasized without the AA filter and *think* they are getting more sharpness, when in fact that is an artifact. They also are missing that for every apparent sharp detail they see, they lose two equivalent details -- irretrievably. (A blue detail that images on a blue sensel is over emphasized, and a blue detail that images onto a red sensel or onto a green sensel is lost forever and cannot *ever* be recovered. This, and the need for AA-filters is very well understood in the signal processing world.)

AA filters preserve information at that detail level by directing the information to sensels that can record it.

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting. When the D850 was announced I was tempting to (try to) purchase one, especially because Nikon had added a number of features I had suggested to them back in 2015, but I ended up instead buying a used D800 *because* it has an AA filter. The D800's AA filter is too weak so with sharp lenses I still get AA artifacts, but the artifacts are weaker than those from the D810.

I to get AA artifacts with the D800

And, with the 50mm/1.4{d or g} wide open on the D800, I get a very nice and smooth transition without AA artifacts at the pixel level. (Unfortunately, ugly artifacts return after stopping those "soft" lenses down just a bit. :-( )

Personally, I'd prefer to go the other way. I'd choose a camera with a full-strength AA-filter over an AA-less, or partial strength AA filter.

 

[John Sheehy]

aflundi wrote:
The D800's AA filter is too weak so with sharp lenses I still get AA artifacts, but the artifacts are weaker than those from the D810.

I to get AA artifacts with the D800

Don't we have enough bad terminology already in photography?

"AA artifacts" would refer to artifact caused by an AA filter, not ones prevented by it (aliasing artifacts; not anti-aliasing artifacts).

This reminds me of all the people who when first hearing of the concept of manual Av and Tv values with auto-ISO, immediately called it "ISO priority", which is actually the total opposite of what it is, where ISO has the least priority.

 

[aflundi]

aflundi wrote:
The D800's AA filter is too weak so with sharp lenses I still get AA artifacts, but the artifacts are weaker than those from the D810.

I to get AA artifacts with the D800

Don't we have enough bad terminology already in photography?

"AA artifacts" would refer to artifact caused by an AA filter, not ones prevented by it (aliasing artifacts; not anti-aliasing artifacts).

This reminds me of all the people who when first hearing of the concept of manual Av and Tv values with auto-ISO, immediately called it "ISO priority", which is actually the total opposite of what it is, where ISO has the least priority.

You're right. I didn't catch my sloppy first-pass on that. I should have said what I virtually always say -- "Aliasiing artifacts". Thanks for the correction.

 

[J A C S]

The anti-aliasing filter is there to stop aliasing. Aliasing is a phenomenon that occurs when there is captured detail finer than the pixel array can deal with. What happens is that this incomplete data can interact to produce patterns in the photo that aren't there in the real image. The most obvious one is 'Moire', which is bands or ring patterns in the image, and is particularly visible when it interacts with the colour filter array to produce coloured bands. However, 'Moire' is not the only form of aliasing, you also get 'jaggies', step in lines that should be smooth, and often subtle changes in texture, sand that looks like lawn, velvet that looks like grit, etc.

However, an aliased image can look subjectively sharper, and this has become a fashion to which some camera manufacturers pander.

I knew we're in trouble when Leica M9 came out without a filter.

Good for you!

It had unreal aliasing and every review looked at all that ugly aliasing... and praised the camera for it's outstanding "detail and per pixel sharpness".

source: IR


aliased pattern






color moiré, M9 on the left






aliasing fest (from the Dave's box)






something less obvious to a non-discriminating observer: specular aliasing

 

[Reilly Diefenbach]

Can someone explain to me why a camera having NO AA filter is a good thing. If I understand correctly, NOT having it can make for sharper photos. But if that's the case, why is it still there on certain cameras?

Marketing departments see that cameras without AA filters sell better. Companies can only survive if they can sell their products.

Nikon, Pentax, Hasselblad, Leica, Phase One, Sony, Oly, Panasonic, all agree, as do all known reviewers and a large proportion of the buying public. Better detail without the AA filter. You couldn't give me a camera with an AA filter at this point, spoiled as I am by the refined presentation of fine detail on offer:




D800 vs D800e

Case closed You guys can discuss it all you want, but if you want a new camera...

I've shot over a hundred thousand shots with a D800e and now a D850, and maybe once had to apply spot moire brush. Of course, I don't shoot silk fabric or air filters for a living.

From a technical side though, it's insane to drop the AA filters.

The AA filter should more accurately be called a blur filter, which is exactly what it does. If you prefer the blur, unsharpen your pics.

The customers see something at the pixel-level that is more strongly emphasized without the AA filter and *think* they are getting more sharpness, when in fact that is an artifact.

It is not. Pixels are what they are. You can't blame pixels for being square. You might as well holler at your 1080p TV for not having four times the pixels.

They also are missing that for every apparent sharp detail they see, they lose two equivalent details -- irretrievably. (A blue detail that images on a blue sensel is over emphasized, and a blue detail that images onto a red sensel or onto a green sensel is lost forever and cannot *ever* be recovered. This, and the need for AA-filters is very well understood in the signal processing world.)

AA filters preserve information at that detail level by directing the information to sensels that can record it.

As if by magic.

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting.

Show us one.

When the D850 was announced I was tempting to (try to) purchase one, especially because Nikon had added a number of features I had suggested to them back in 2015, but I ended up instead buying a used D800 *because* it has an AA filter. The D800's AA filter is too weak so with sharp lenses I still get AA artifacts, but the artifacts are weaker than those from the D810. And, with the 50mm/1.4{d or g} wide open on the D800, I get a very nice and smooth transition without AA artifacts at the pixel level. (Unfortunately, ugly artifacts return after stopping those "soft" lenses down just a bit. :-( )

Personally, I'd prefer to go the other way. I'd choose a camera with a full-strength AA-filter over an AA-less, or partial strength AA filter.

Just go to minus sharpening if you can't stand the unadulterated pixels.

 

[aflundi]

From a technical side though, it's insane to drop the AA filters.

The AA filter should more accurately be called a blur filter, which is exactly what it does. If you prefer the blur, unsharpen your pics.

I'm going to limit my response here and not answer all your challenges as this area is very well understood. I'll start you off by pointing out that the blur *must* happen *before* sub-sampling. If it isn't, the information is lost. Blurring after the sub-sampling can't recover the lost information.

There are lots and lots of text books, heck, even Wikipedia that cover this material. Many basic photography courses also cover this subject. This is very basic.

...

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting.

Show us one

Ok, though I suspect this is not a "good faith" request, this *one* time.


D810 with 50mm/1.4D at f/1.4

You have more than enough to question your initial intuitions and to get started understanding sub-sample theory and aliasing.

 

[J A C S]

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting.

Show us one.

This is a crop from a A7R shot with the Canon 50L at f/1.2, off center, posted here by another user:

 

[Reilly Diefenbach]

From a technical side though, it's insane to drop the AA filters.

The AA filter should more accurately be called a blur filter, which is exactly what it does. If you prefer the blur, unsharpen your pics.

I'm going to limit my response here and not answer all your challenges as this area is very well understood. I'll start you off by pointing out that the blur *must* happen *before* sub-sampling. If it isn't, the information is lost. Blurring after the sub-sampling can't recover the lost information.

There are lots and lots of text books, heck, even Wikipedia that cover this material. Many basic photography courses also cover this subject. This is very basic.

...

BTW, I've had a Nikon D810 since shortly after it was introduced. It's a fantastic camera, but I've been disappointed to discover that even my softest lenses (say a Nikon 50mm/1.4d at f/1.4 for instance) still produces significant AA artifacting.

Show us one

Ok, though I suspect this is not a "good faith" request, this *one* time.


D810 with 50mm/1.4D at f/1.4

You have more than enough to question your initial intuitions and to get started understanding sub-sample theory and aliasing.

I have zero interest in theory, only what my pics look like on the peep. The sharpening routines for the AA equipped cameras (D750, D800, D7000, etc.) are difficult and unsatisfactory, with a fair bit of actual artifacts creeping in as the user attempts to reconstruct detail thrown out by the OLPF. The AA free cameras are simple and easy to get refined detail by comparison. You can't see that, we get it, but I for one will not be dragged down by theoretical concerns.

It is certainly possible to find examples of moire from any camera, AA or no. It's just that 99% of us want our pictures without the blur. If I were taking pictures of venetian blinds at a thousand feet or yards and yards of fabric, I would probably on here with the one percenters futilely agitating for the return of the AA filter. Most of us are over moire. And, as mentioned, the debate is over.

 

[aflundi]

Show us one

Ok, though I suspect this is not a "good faith" request, this *one* time.


D810 with 50mm/1.4D at f/1.4

You have more than enough to question your initial intuitions and to get started understanding sub-sample theory and aliasing.

I have zero interest ... And, as mentioned, the debate is over.

Just as I suspected. My conversion with you is over as well. Best of luck to you.

 

[Reilly Diefenbach]

Show us one

Ok, though I suspect this is not a "good faith" request, this *one* time.

You have more than enough to question your initial intuitions and to get started understanding sub-sample theory and aliasing.

I have zero interest ... And, as mentioned, the debate is over.

Just as I suspected. My conversion with you is over as well.

Spoken like a true Unix SysAdmin.

Best of luck to you.

Thank you very much. I am unable to wish you luck with your OLPF jihad, however, as all known manufacturers have made the carefully considered decision several years ago to banish it to the dustbin and not get neurotic about moire or search it out with fresnel discs. And most importantly, know that my pics will always contain more and better detail than yours unless you're using that instrument of the devil, the D850.

 

[coudet]

I knew we're in trouble when Leica M9 came out without a filter.

Good for you!

It had unreal aliasing and every review looked at all that ugly aliasing... and praised the camera for it's outstanding "detail and per pixel sharpness".

source: IR

Available in 1920x1080 if anyone wants a moire wallpaper