# Anti-Aliasing Filter-less DSLRs.



## Markw (Jan 17, 2012)

There are rumors circulating about, you've all heard them, that the D800 will come in two models; one with the AA filter removed.  

Now, I don't really fully understand the implications of this.  I do know, however, that there are companies out there that will remove the filter for you (click).  To my understanding, the filter intentionally takes some of the detail out of the photo in order to inhibit moiré.  I hear that the high-resolution 36MP sensor of the D800 will be so much so that it will get rid of the moiré risk; thereby ridding the camera for the need of a filter in the first place.  

To me, it looks like this can only be a good thing.  It will render your lenses much sharper than their AA-filtered counterparts, and will bring out much more detail.  But, if this were the case, why would they offer a D800 model with the filter at all?  There has to be some drawback I'm missing.  

As you can tell, I'm a bit unknowledgeable about this concept.  So, if you could help me out in understanding the implications of having, and not having the filter, I'd greatly appreciate it, since the camera will likely be announced shortly.

Thanks!
Mark


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## Overread (Jan 17, 2012)

A part of me is wondering if this isn't just the general sharpness addicts crowed rumour milling about the idea of losing the AA filter and getting even purer sharper images. IF they were to do two releases it would strongly suggest to me that the lack of the AA filter was leading to a detrimental effect - thus meaning that the AAfilter-less edition would be targeted at a specific segment of the market for which moire might be a lesser issue in what they shoot.


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## KmH (Jan 17, 2012)

Anti-aliasing filter - Wikipedia, the free encyclopedia

Low-pass filter - Wikipedia, the free encyclopedia


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## Helen B (Jan 17, 2012)

The new Fuji Pro-X1 doesn't have an AA filter, I believe. It does have an unusual filter matrix instead - it isn't regular like the Bayer filter on most cameras. It's not a DSLR, however.


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## nickzou (Jan 18, 2012)

Helen B said:


> The new Fuji Pro-X1 doesn't have an AA filter, I believe. It does have an unusual filter matrix instead - it isn't regular like the Bayer filter on most cameras. It's not a DSLR, however.



Yeah.... that new rangefinder looks sexy... Speaking of rangefinders, I'm pretty sure the the Leica M9 also does not have an AA filter.


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## unpopular (Jan 18, 2012)

There is a rumor that the A99 and the D800 will share the same sensor, there is also a rumor that the a99 will be a 3mos configuration. I sort of really doubt that will be the case, a full frame 3mos assembly would be huge. Perhaps though Sony is producing some kind of maskless sensor that would make an AA filter obsolete and perhaps explain - perhaps disappointingly - the somewhat outlandish 36mp figure.

I very much doubt there will be two versions. Two versions means two production paths. Manufacturing at this scale isn't as easy as "leaving some out".


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## Markw (Jan 18, 2012)

unpopular said:


> I very much doubt there will be two versions. Two versions means two production paths.



D3-->D3s + D3x.

Mark


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## KmH (Jan 18, 2012)

So far that has only happened in Nikon's Dx series cameras. It has never happened in the Dxxx series.

The D3s was just an interim update to the D3, while the D3x was developed specifically for the studio shooter.

But, everything online about the D800(?) is still just speculation at this point.


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## Patrice (Jan 18, 2012)

nickzou said:


> The new Fuji Pro-X1 .........
> 
> Yeah.... that new rangefinder looks sexy... Speaking of rangefinders, I'm pretty sure the the Leica M9 also does not have an AA filter.




The Fuji Pro-1, although it has a certain body shape that is similar to a rangefinder cameras, it is not a rangefinder. 'Rangefinder' refers to a type of manual focusing system.


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## unpopular (Jan 18, 2012)

Patrice said:


> nickzou said:
> 
> 
> > The new Fuji Pro-X1 .........Yeah.... that new rangefinder looks sexy... Speaking of rangefinders, I'm pretty sure the the Leica M9 also does not have an AA filter.
> ...


How will it focus then? I always thought it would be an electronic rangefinder, like the Contax G2? Will it just be contrast detect or use phase detect similar to the F300 EXR?


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## Crollo (Jan 18, 2012)

I will never understand how people seem to believe the megapixel count is a easy singular dictator for image resolution and sharpness... If the lens can't resolve the proper level of detail for a 80MP sensor then you're going to have a 2MP image. You cannot just upgrade the MP count and suddenly moire is gone.


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## unpopular (Jan 18, 2012)

Crollo said:


> I will never understand how people seem to believe the megapixel count is a easy singular dictator for image resolution and sharpness... If the lens can't resolve the proper level of detail for a 80MP sensor then you're going to have a 2MP image. You cannot just upgrade the MP count and suddenly moire is gone.


2mp? Are you using a potato? I'll have to think about the moire issue...


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## Garbz (Jan 19, 2012)

There's a couple of things anti-aliasing does for cameras, and believe me they are positive, not negative, or do you think Nikon / Canon intentionally cripple their cameras? 

Firstly there's the Moire effect that comes from recording a repeating pattern with a grid of pixels. A minor reduction in sharpness is greatly preferred to a photo which ultimately looks like this which is one of the two things the AA filter tries to avoid:






The effect of the AA filter not only solves the horrendous edges on patterns, but it also helps details which are too small to render as a pixel on an image contribute to the final image. Yes the result is not "sharp" but at least it doesn't look weird either. This is best illustrated with a computer game as per this GIF: http://h9.abload.de/img/antialiasing0qbuf.gif . Now take a look at the TV antenna on the left building. Would you rather a slightly less sharp TV antenna or an antenna that is so sharp that parts of it aren't actually visible and other bits appear out of nowhere?

Thirdly the AA filter addresses an issue of how we grade the megapixels of a camera. Most sensors have a beyer pattern which is interpolated to give us a final image. That means our 12 mpxl cameras doesn't have 12 million RGB pixels, they actually have 6million green, 3million red, and 3million blue pixels. The software interpolation then makes this a 12mpxl image. The AA filter is designed in a way to ensure that if any signal light point is small enough to hit a signal pixel it is diffracted across any group of 4. This is where the supposed problems with sharpness come in. The reality is that while removing the AA filter does increase the sharpness, any detail you gain runs the risk of not being recorded across 2 green, one red, and one blue pixel and thus results in incorrect colour. A good example of an AA filter that isn't well matched to the camera is the Canon 5DmkII which produces rainbow patterns on greyscale images when aliasing occurs:






So rumours.... yes rumours is likely all they will be. Unless Nikon has some crazy sensor design that isn't laid out in a grid, or just wants to piss quality against the wall, sure. The problem is that aliasing is always a problem. As the sensor resolution increases it just means the new finer detail will start to suffer aliasing effects. I hope this isn't an acknowledgement from Nikon that they don't have a lens sharp enough to resolve their new sensor because while that would allow the camera to work without an AA filter it would also be incredibly funny.


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## unpopular (Jan 19, 2012)

I believe that it is very likely though that the masked sensors are not the way of the future. They are so tremendously problematic and truly represent the majority of problems we're seeing in DSLRs today.

Eventually I think there will be a drive away from this antiquated technology. I don't know if it will be the with the d800 generation or not, but eventually it's just going to have to happen one way or another.


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## Markw (Jan 19, 2012)

That was a wonderful description Garbz, thank you for that!  But, is there no chance since there will be 36MP jammed into the sensor, that the light will diffract the light enough to hit the correct color pixels, and the aliasing won't be a problem?  I'm not 100% certain how this would affect the moiré issue, but for aliasing, this seems like it would fix most of the problem, if I understand the problem correctly in the first place.

My only disgruntle is that I can't believe Nikon would produce a camera to the caliber of their Dxxx line, and hinder the ability of it to do what it is supposed to do, take proper photos.  I think if we all know it would be a waste of R&D funds, and production funds, then charge an extra $900 for the camera without the filter, and it still had such serious problems as aliasing, they know it, and they wouldn't make it if that were the case...

Mark


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## Derrel (Jan 19, 2012)

Garbz said:
			
		

> T



Cool sample photos,bro. I plan to drink a few beers this weekend, and stare at these two shots for a while.


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## unpopular (Jan 19, 2012)

^^ "beers" huh?


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## Derrel (Jan 19, 2012)

The Kodak 14n and its various derivatives were free of AA filter arrays. That camera had one heck of a lot of sensor problems...the problems were legion...

The Leica M-series rangefinders are all as I recall, free of AA filters; a good number of people have made posts on the interwebs, stating that in their opinion Leica got about the same overall resolving power out of an 18MP sensor without an AA filter as the Nikon D3x did with a 24.6 MP Sony-sensor equipped with an AA filter.

I honestly doubt that the majority of 35mm system lenses are going to play nicely with a 36MP FF sensor, especially at even remotely smallish apertures...I'm tired and headachy today and can't think all that great, but my thought is that f/4 is going to be about as small an aperture as one will be able to go before diffraction sets in on a 36MP 24x36 sensor that's free of an AA filter...I really do not see the benefit of that many Megapixels on a camera like a D800...I just do not think the "majority" of lenses will be able to utilize that high of an MP count at the apertures where the lenses are at their best...


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## unpopular (Jan 19, 2012)

I think small format is just kind of a dead horse. It just does not make much sense to keep cramming more and more pixels onto a small format - it doesn't make sense from a manufacturing POV, an optical POV or an electronic POV.

One of these manufacturers is going to build a medium format body, then instead of a race to see how many pixels you can cram onto a 35mm frame, it will be who can build the biggest sensor.

They'll be making a new line of lenses every three months!


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## Markw (Jan 19, 2012)

That's what I said on a recent NR thread.  I don't see why Nikon hasn't already made a MF sensor, or a sensor between FX and MF.  Something like a 0.9x crop factor, or a little less, at 16-20MP instead of 30-60MP would create a camera with incredible dynamic range, and incredible ISO capabilities to boot.  Making a mid-level sensor size between FX and MF would allow them to keep processing time down, frame rates relatively up (combined with the low-ish MP count).  It'd be an incredible camera.  I'd definitely have one. 

Mark


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## Patrice (Jan 19, 2012)

I, for one, would think long and hard before buying into a larger digital format from Nikon. I have a cupboard full of Nikon glass dating back a few decades and all of them can be used on all the Nikon bodies I presently own. A larger format would render more than a few of these way less useful than they presently are.

Besides, there are already quite a few choices if you want a sensor bigger than 35 by 24 but smaller than 60 by 60.


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## eric-holmes (Feb 6, 2012)

Looks like the rumors were right about the D800E.


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## Garbz (Feb 7, 2012)

Markw said:


> That was a wonderful description Garbz, thank you for that!  But, is there no chance since there will be 36MP jammed into the sensor, that the light will diffract the light enough to hit the correct color pixels, and the aliasing won't be a problem?  I'm not 100% certain how this would affect the moiré issue, but for aliasing, this seems like it would fix most of the problem, if I understand the problem correctly in the first place.
> 
> My only disgruntle is that I can't believe Nikon would produce a camera to the caliber of their Dxxx line, and hinder the ability of it to do what it is supposed to do, take proper photos.  I think if we all know it would be a waste of R&D funds, and production funds, then charge an extra $900 for the camera without the filter, and it still had such serious problems as aliasing, they know it, and they wouldn't make it if that were the case...
> 
> Mark



The thing is Moire is a very specific problem in a number of usage cases. It's a problem that can be mostly eliminated in post processing but is very hard to do for video. There are several applications where moire will likely never be a problem. One of the specific ones is photographing nature, specifically landscapes. Under the assumption that you don't have a repeating fine pattern in the image, your lens is sharp enough, and you're shooting where diffraction is a non issue then you can achieve a sharper photo without an AA filter. However for a general purpose camera something as simple as a tiled roof can generate problems. In the general purpose case yes no AA filter can be crippling in many scenarios. In the specific case you can squeeze more performance out of your gear. 

Having extra resolution really helps too. The higher resolution changes the Nyquist frequency and thus requires a finer pattern to generate a moire effect. Combined with the imperfections in a typical lens, and the diffraction effects limiting sharpness you end up with something that may not be field relevant. However a word of caution, if the lens and diffraction causes moire not to occur than you're likely looking at a combination which wouldn't benefit from having the AA filter removed either. In any case I'm pleased to see that they have opted to offer both options to end users. 

Video users looking at the D800 as Nikon's answer to the 5DmkII would definitely opt for one with an AA filter. It is very hard to edit out moire effects in post processing in video, and the BBC have effectively banned the use of a 5DmkII from more than 25% of any program shoot due to the poor performance with moire. Case by case exceptions were granted, but in cases where you're photographing people wearing cloths moire can appear suddenly and without warning. Take a step closer and it can disappear, take a step further away and it can also disappear.


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