removing the AA filter

[Plekto]

so this is  film techniques and formulas applied to digital...surely many things can be learned.  thanks.

True.  Analog to digital techniques always are a kludge, and that's the main problem with the Bayer pattern - it requires a bunch of massaging of the data to deal with the problems.

Yes of course, but we see no jaggies at actual pixels. Three possible explanations

The reason is because the Foveon sensor bleeds between each pixel location like film or dye-sub printers do(almost zero space between the locations), so unless it's a hard line, you'll never likely notice it.  OTOH, if you look at a dark scene with sunlight in it(say under a bridge looking out at the lighter distance), the Foveon sensor has horrendous *everything* that you can think of along that line where the two meet.  This is exacerbated by the low DR as well.  Its very sensitive to white levels, but if that's even close or there aren't hard to deal with issues, it's awesome.  It, IMO, is the best sensor made to date for outdoor scenery.  Kind of like having Velvia 50 always in your camera and never using anything else.  Nothing better when it's in its element but pretty much give up using it for interiors or low light barring a tripod and a lot of pushing the exposure.(and praying as any SD series user will attest to - heh )

IMO, the Fuji is the better compromise.  Crazy high DR and film like shoulder, plus very little noise and artifacts.   I originally was THE biggest Foveon fan out there but the sobering truth is that you can do so much more with the Fuji.  If only it wasn't like a... well, it's kind of like giving a person an eye dropper of hundred year old Brandy.  It's almost cruel in a way...      Double the MP would be enough, and full frame would just about do that for them.

For the SD14, maybe it is a slight detail that is "smudged" out
For the 50D, It is the entire image that is fuzzy, and making detail ares indistinguishable.

As for this comment, it's actually the reverse.  The reason the SD14 looks smudged out is because it's hit a hard wall.  The locations are spaced right next to each other like film and so when it hits that limit, it resolves nothing more.  It's not smudged but is suffering from myopia/is truly fuzzy.  The more you push the Foveon as a result, the less in-focus tiny details become.  But it still blurs consistently as every color channel is identical in resolution.  

The 50D is suffering from different channels having different resolution.  This causes horrendous aliasing and artifacts in tiny details.  The software tries it butt off to fix this, but it's not truly fixable unless the pixels are so tiny that single points of garbage are too small to see individually(which the 24MP cameras come close to, btw)  The end result is that the camera smudges the detail to smooth it out.  So areas look great and areas also look bad in the same image.

There is no free lunch.  Both technologies have things that you love and hate.  

[Phil Indeblanc]

Hi Erik,

this last post on my first read has a lot of meat in it.  I think I will need to read it 2 or 3 times to graps it well enough.  So far the first part I got, not a problem...I understand it

I will need to read the rest with more care.  I am following, but need a better understanding.

I know deffraction as I have many times been puzzled, then I understood.  But what you say regarding the spacing will vary from each camera model , i would think.
So if we know the spacing of the Kodak SLRc, we can match it with a lens so we get the zigzag instead of the smear...As I think the zigzag maybe easier to handle?
The interesting thing is the 50D has NO space between the microlens. although these are atop the photons, or what ever they are called...maybe that is still the issue.


Lots to think about...BUT

In my experience I like the aliasing file, as I think it is the AA blurring that takes away from the "polish" look, even with the zigzag on occasion...Besides, it is NOT the aliasing that makes it look good.  Because Daniel, you explanation of "people liking it" sounds like it is the aliasing they like....NO, it is the lack of the AA they like....I think.

OK, I will read a few more times later and post. :-)

[Phil Indeblanc]

True.  Analog to digital techniques always are a kludge, and that's the main problem with the Bayer pattern - it requires a bunch of massaging of the data to deal with the problems.


The reason is because the Foveon sensor bleeds between each pixel location like film or dye-sub printers do(almost zero space between the locations), so unless it's a hard line, you'll never likely notice it.  OTOH, if you look at a dark scene with sunlight in it(say under a bridge looking out at the lighter distance), the Foveon sensor has horrendous *everything* that you can think of along that line where the two meet.  This is exacerbated by the low DR as well.  Its very sensitive to white levels, but if that's even close or there aren't hard to deal with issues, it's awesome.  It, IMO, is the best sensor made to date for outdoor scenery.  Kind of like having Velvia 50 always in your camera and never using anything else.  Nothing better when it's in its element but pretty much give up using it for interiors or low light barring a tripod and a lot of pushing the exposure.(and praying as any SD series user will attest to - heh )

IMO, the Fuji is the better compromise.  Crazy high DR and film like shoulder, plus very little noise and artifacts.   I originally was THE biggest Foveon fan out there but the sobering truth is that you can do so much more with the Fuji.  If only it wasn't like a... well, it's kind of like giving a person an eye dropper of hundred year old Brandy.  It's almost cruel in a way...      Double the MP would be enough, and full frame would just about do that for them.


As for this comment, it's actually the reverse.  The reason the SD14 looks smudged out is because it's hit a hard wall.  The locations are spaced right next to each other like film and so when it hits that limit, it resolves nothing more.  It's not smudged but is suffering from myopia/is truly fuzzy.  The more you push the Foveon as a result, the less in-focus tiny details become.  But it still blurs consistently as every color channel is identical in resolution.  

The 50D is suffering from different channels having different resolution.  This causes horrendous aliasing and artifacts in tiny details.  The software tries it butt off to fix this, but it's not truly fixable unless the pixels are so tiny that single points of garbage are too small to see individually(which the 24MP cameras come close to, btw)  The end result is that the camera smudges the detail to smooth it out.  So areas look great and areas also look bad in the same image.

There is no free lunch.  Both technologies have things that you love and hate.  

One of your better posts that help me understand :-)

thank you

[joofa]

so this is  film techniques and formulas applied to digital...surely many things can be learned.  thanks.

I don't want to give an impression that there is some analog formula that gets applied to digital. Fourier transform of sampled system (discrete system) is continuous and periodic, where as the way 2D->1D Fourier transform is taken in NTSC TV analog signal it makes it (approximately) discrete in the frequency domain. Now isn't that interesting that a discrete system has a continuous waveform in frequency domain and an analog signal treated in a certain way has a discrete representation. And, there is a close relationship between such continuous/discrete representations in the frequency domain. Don't let the Discrete Fourier Transform (DFT) of a discrete signal confuse you as it assumes certain periodicities in the spatial domain that makes it discrete in the frequency domain, and again there is a close relationship of the DFT to above mentioned continuous/discrete frequency representations.

Anyway, I'm getting boring here so lets change gears, and suffice it to say once you bring stuff into frequency domain then the usual notion of aliasing starts making sense and one sees that luma/chrom leaking (aliasing) into each other for both analog and discrete systems results in similar observations.

Bayer CFA may be considered as a combination of luma and 2 chroma components derived using a certain linear combination of RGGB CFA values. NTSC TV signal also has a luma and 2 chroma components (YIQ/YUV), but of course derived using different weights in the linear combination of RGB. And, these nasty beasts leak (alias) into each other resulting in luma/chroma aliasing.

For e.g., haven't we seen those "color fringing" in digital photos for high detail scenes (luma aliasing into chroma). Now compare to those "color patterns" that result in NTSC TV for high detail scenes.  When chroma aliases into luma the digital photos start having those dots, where as NTSC TV signal has those "crawling dots".

[Phil Indeblanc]

Anyway, I'm getting boring here so lets change gears, and suffice it to say once you bring stuff into frequency domain then the usual notion of aliasing starts making sense and one sees that luma/chrom leaking (aliasing) into each other for both analog and discrete systems results in similar observations.

Bayer CFA may be considered as a combination of luma and 2 chroma components derived using a certain linear combination of RGGB CFA values. NTSC TV signal also has a luma and 2 chroma components (YIQ/YUV), but of course derived using different weights in the linear combination of RGB. And, these nasty beasts leak (alias) into each other resulting in luma/chroma aliasing.

For e.g., haven't we seen those "color fringing" in digital photos for high detail scenes (luma aliasing into chroma). Now compare to those "color patterns" that result in NTSC TV for high detail scenes.  When chroma aliases into luma the digital photos start having those dots, where as NTSC TV signal has those "crawling dots".

Ya, that first part...I am sure other with some insight appreciate it, but....

So the Luma Chroma interesting...

But lets get off the history lesson, and try to see if there is anything we can conclude....

So far NOT.

We DO know that this artifact occurs....Now to see how significant it is.  And can we not consider the effects of the AA a imposed artifact?
and lastly....

how these 2 plays into photography in the hands of someone who knows what they are doing?

I honestly see little importance to this in 50% of shooting in the "PROFESSIONAL" level (excluding event shooters, and other mediums that have no need for extreme detailed images).

I believe this is interest more towards...

Firstly a very fussy group. A group that always questions themselves and how they can improve their work, their gear, etc...Looking to always do better.
These are good things I believe, so Then there are studio shooters of cars, or jewelry, of product, of faces, of landscapes, of scientific areas, that this DOES play a somewhat IMPORTANT part of imagery....Of course this is all AFTER you have your skill as a shooter as second nature).

[jing q]

One thing to point out is that aliasing maybe gets a worse rap than it deserves.

Perhaps some people like aliasing. Images produced by cameras in the first place are not accurate to the way normal vision perceives images.

I like a certain amount of aliasing for some of my work.

[Phil Indeblanc]

One thing to point out is that aliasing maybe gets a worse rap than it deserves.

Perhaps some people like aliasing. Images produced by cameras in the first place are not accurate to the way normal vision perceives images.

I like a certain amount of aliasing for some of my work.

Exactly, so lets see a couple tests, and see how much it bothers the visual.  So far the very thin vertical line is a NON issue for me (The one Erik points out).  but if at 100% the other thicker line...if that is visible to the eye as jigjag, then it maybe something to treat in PS.  If that is ALL the little artifacts that aliasing does, Perhaps it isn't a issue. And I want to see a example where aliasing is preferred?  
I think the entire picture is what looks better, and perhaps not the alaising in particular areas.  So far more people like to see a NON AA filter according to Damiel, and I think it makes sence, since everything is more clear, with a couple slight issues in a few detail spots.  Maybe hair in a portrait might be a problem....we can only see results from images taken.  Not becasue aliasing occures, therefore we should use AA which in my observations degrades the ENTIRE image.

[ErikKaffehr]

Hi,

I'd like to point out some issues I think you miss.

1) Resolution on 24 MP cameras is essentially like 10 MP on APS-C. The 5D and the 7D get much closer to oversampling than any any other DSLR, except for 4/3. I presume that you talk about full frame regarding 24 MP because there are no 24 MP APS/C cameras. MFDBs are a different thing.

2) The bayer pattern is a pretty close approximation of the fovea. Our vision is based on color sensitive cones, which at least have some similarity i to the "Bayer" patten. I'm not advocating that mother nature is always correct, but a "Bayer pattern" like solution was choosen by it.

3) Half of the "Bayer pattern" pixels are green, so half of the luminance information is non interpolated. Once the images are converted to JPEG much of the color information is disposed of anyway, so I'd guess that once we have JPEG the amount of chroma information may be similar between "Foveon" and "Beyer".

There is one obvious advantage of Foveon over Bayer, and that is that color Moiré patterns would not arise with Foveon. For that reason Foveon can be used without an AA filter, without artifacting being obvious. Monochrome aliasing in sensors depends only pixel pitch, fill factor and AA-filtering. As Foveon sensors have low Pixel count (that is large pitch) it is obvious that they would alias more than smaller pitch sensors having similar fill factors.

My guess is that the Foveon concept may have a problem with noise and color reproduction. Bayer solutions use filters arrays with spectral characteristics that can be optimized . The Foveon concept is based on diffusion of different wavelengths to different depth. Therefore I presume that it's capability to differentiate colors is somewhat limited. It is quite possible that Foveon has not move to increased resolution because of issues with noise at high ISOs

There may be be two reasons that the "Foveon" concept did not catch on:

1) It may be that the disadvantages outweight the advantages
2) Intelectual propert issues

Best regards
Erik Kaffehr

True.  Analog to digital techniques always are a kludge, and that's the main problem with the Bayer pattern - it requires a bunch of massaging of the data to deal with the problems.


The reason is because the Foveon sensor bleeds between each pixel location like film or dye-sub printers do(almost zero space between the locations), so unless it's a hard line, you'll never likely notice it.  OTOH, if you look at a dark scene with sunlight in it(say under a bridge looking out at the lighter distance), the Foveon sensor has horrendous *everything* that you can think of along that line where the two meet.  This is exacerbated by the low DR as well.  Its very sensitive to white levels, but if that's even close or there aren't hard to deal with issues, it's awesome.  It, IMO, is the best sensor made to date for outdoor scenery.  Kind of like having Velvia 50 always in your camera and never using anything else.  Nothing better when it's in its element but pretty much give up using it for interiors or low light barring a tripod and a lot of pushing the exposure.(and praying as any SD series user will attest to - heh )

IMO, the Fuji is the better compromise.  Crazy high DR and film like shoulder, plus very little noise and artifacts.   I originally was THE biggest Foveon fan out there but the sobering truth is that you can do so much more with the Fuji.  If only it wasn't like a... well, it's kind of like giving a person an eye dropper of hundred year old Brandy.  It's almost cruel in a way...      Double the MP would be enough, and full frame would just about do that for them.


As for this comment, it's actually the reverse.  The reason the SD14 looks smudged out is because it's hit a hard wall.  The locations are spaced right next to each other like film and so when it hits that limit, it resolves nothing more.  It's not smudged but is suffering from myopia/is truly fuzzy.  The more you push the Foveon as a result, the less in-focus tiny details become.  But it still blurs consistently as every color channel is identical in resolution.  

The 50D is suffering from different channels having different resolution.  This causes horrendous aliasing and artifacts in tiny details.  The software tries it butt off to fix this, but it's not truly fixable unless the pixels are so tiny that single points of garbage are too small to see individually(which the 24MP cameras come close to, btw)  The end result is that the camera smudges the detail to smooth it out.  So areas look great and areas also look bad in the same image.

There is no free lunch.  Both technologies have things that you love and hate.  

[Daniel Browning]

There is one obvious advantage of Foveon over Bayer, and that is that color Moiré patterns would not arise with Foveon. For that reason Foveon can be used without an AA filter, without artifacting being obvious.

I disagree. The aliasing is certainly still "obvious" -- the only question is whether you consider that obvious part of the image as a hideous artifact or beautiful detail. The Foveon image I posted above has only luma aliasing, and to me it is horribly disfigured with artifacts. Yet Phil looks at the same image and he feels that it is highly attractive with sharpness.

If what you meant is that luma aliasing is less ugly than chroma aliasing, I would agree. I think a lot of people who are in love with luma aliasing actually dislike chroma aliasing. (That's why my first demonstration in this thread only had luma aliasing.)

Furthermore, there may be another factor that you did not consider. In most photos taken with filtered Bayer images, chroma aliasing is not a big issue. It's only certain subjects and conditions where the chroma aliasing becomes as objectionable as unfiltered cameras (which have both strong luma and chroma aliasing). In those conditions, it's possible to use a demosaic algorithm that relies much more heavily on the anti-aliased luma signal to avoid aliasing in the chroma signals. The trade off is reduced resolution (especially chroma resolution). Graeme Nattress did this for RED's raw converter.

In other words, the filtered Bayer chroma aliasing problem is well-resolved for all but the most extreme corner cases, making it much less of a weakness in comparison to alternatives like Foveon. (The most important weakness of Bayer is the loss of so many stops of light to color filters, but so far no alternative has proven superior in this regard, including Foveon. Maybe microprisms some day...)

[ErikKaffehr]

Hi,

I'd suggest that it is pretty obvious that luma aliasing is not obvious to quite a few observers, at least judging from the writing on these forums.

Regarding the loss of light in filters I'd guess it is unavoidable as colored light needs to split up so it can be detected by different sensors. As long as filtering is involved light will be lost.

Best regards
Erik

I disagree. The aliasing is certainly still "obvious" -- the only question is whether you consider that obvious part of the image as a hideous artifact or beautiful detail. The Foveon image I posted above has only luma aliasing, and to me it is horribly disfigured with artifacts. Yet Phil looks at the same image and he feels that it is highly attractive with sharpness.

If what you meant is that luma aliasing is less ugly than chroma aliasing, I would agree. I think a lot of people who are in love with luma aliasing actually dislike chroma aliasing. (That's why my first demonstration in this thread only had luma aliasing.)

Furthermore, there may be another factor that you did not consider. In most photos taken with filtered Bayer images, chroma aliasing is not a big issue. It's only certain subjects and conditions where the chroma aliasing becomes as objectionable as unfiltered cameras (which have both strong luma and chroma aliasing). In those conditions, it's possible to use a demosaic algorithm that relies much more heavily on the anti-aliased luma signal to avoid aliasing in the chroma signals. The trade off is reduced resolution (especially chroma resolution). Graeme Nattress did this for RED's raw converter.

In other words, the filtered Bayer chroma aliasing problem is well-resolved for all but the most extreme corner cases, making it much less of a weakness in comparison to alternatives like Foveon. (The most important weakness of Bayer is the loss of so many stops of light to color filters, but so far no alternative has proven superior in this regard, including Foveon. Maybe microprisms some day...)

[Phil Indeblanc]

I disagree. The aliasing is certainly still "obvious" -- the only question is whether you consider that obvious part of the image as a hideous artifact or beautiful detail. The Foveon image I posted above has only luma aliasing, and to me it is horribly disfigured with artifacts. Yet Phil looks at the same image and he feels that it is highly attractive with sharpness.

Furthermore, there may be another factor that you did not consider. In most photos taken with filtered Bayer images, chroma aliasing is not a big issue.

In other words, the filtered Bayer chroma aliasing problem is well-resolved for all but the most extreme corner cases, making it much less of a weakness in comparison to alternatives like Foveon.

You guys bring up the chroma to luma differences of aliasing, that is a nice thing for the labs to work on and programmers to control. surely good for us all to read and better understand.

Daniel....You are taking things out of contex and amplifying the strengths of BAYER...why?

Photography as a art, or visual medium is eventually the observers domain, and the behind the scenes, digital of how it is presented is very much scientific....(this is loosely stated, as there are scientific and visual benifits as I see to not having AA even with so far the single image we have "inspected")....

Ultimately, the NON AA sensor, looks BETTER, and the aliasing is NOT obvious, as in first you quote the word "obvious" to Cover your a$s, and then use the word to down play the significance.  I don't appreciate that type of language when science is concerned. You become a tech sales support specialist, and help sell a product, OR drive your own agenda.... but not resolve a question.
I appreciate your input:  I would more so appreciate a agressively neutral stance and open to what this all means to Photography and visual appeal.


I will post a few pictures ASAP, of NON AA.  ANY subject you(anyone), would like me to shoot?

[Daniel Browning]

I'd suggest that it is pretty obvious that luma aliasing is not obvious to quite a few observers, at least judging from the writing on these forums.

I did not make myself clear. I agree that many observers consider luma aliasing to be highly desirable, so they do not see it as an image riddled with artifacts.

Daniel....You are taking things out of contex [...]

Sorry, I can't see where I did that. I did not mean to.

[...] and amplifying the strengths of BAYER...why?

I don't think I'm amplifying anything. I simply responded to Erik's assertion that Foveon has an advantage over Bayer when it comes to chroma aliasing. I explained why I think that's only a small advantage.

Ultimately, the NON AA sensor, looks BETTER, and the aliasing is NOT obvious, as in first you quote the word "obvious" to Cover your a$s, and then use the word to down play the significance.  I don't appreciate that type of language when science is concerned.

Sorry, but I don't understand your rant here at all. Maybe it will help if I break it down:

• Erik said "Foveon can be used without an AA filter, without artifacting being obvious".
• I felt that the statement might mislead a reader into thinking that it will not have strong aliasing.
• If Sigma used Foveon with an AA filter (as recommended by the Foveon designers themselves), then one could also say it will not have obvious artifacts.
• So what is the difference between "Foveon with filter has no obvious artifacts" and "Foveon without filter has no obvious artifacts"?
• The difference is that many do not consider luma aliasing to be an artifact.
• So again, Unfiltered Foveon does have obvious aliasing. That is a fact.
• Some consider aliasing to be beautiful and desirable details.
• Others consider aliasing to be ugly and horrible artifacts.
• To clear up this situation, I said "The aliasing is certainly still "obvious" -- the only question is whether you consider that obvious part of the image as a hideous artifact or beautiful detail."

You become a tech sales support specialist, and help sell a product, OR drive your own agenda.... but not resolve a question.

My only agenda is to learn and share about photography.

[Plekto]

Hi,

I'd like to point out some issues I think you miss.

1) Resolution on 24 MP cameras is essentially like 10 MP on APS-C. The 5D and the 7D get much closer to oversampling than any any other DSLR, except for 4/3. I presume that you talk about full frame regarding 24 MP because there are no 24 MP APS/C cameras. MFDBs are a different thing.

Correct.  I was talking about what it would take to match the Foveon if it were scaled to FF.  As it is, it's roughly 10-12MP, and that was fantastic four years ago or so, but now you see pocket consumer cameras with 10-12MP.  That are 5-10X mroe usable since they actually do indoor and night-time shots unlike the SD series.

It's kind of like giving a flawless diamond to your fiance'.  But 1/8th of a carat.  It's awesome to look at, but she's always wondering about the size.  Sometimes bigger and slightly less quality is better.  

[Phil Indeblanc]

My only agenda is to learn and share about photography.

I'm glad to hear that.

I think we have exhausted the ideas, the science, the theories and just about all other measure, except for a mix of image samples of different subjects without an AA that exhibits artifacts that are disruptive of the image.

So far we have viewed a very extreme or exagerated image of aliasing, Danial's posted image.  This helps us better define ...aliasing/artifact  (I see that aliasing is an artifact, but not really synonimous).
Second images....lead us to take a different turn into comparing apples and oranges....We put some energy into this, but at the end of the day, we beat up a dead horse...sort of.  At least it create more dialogue to understand a few things better.

So...We need NON AA images, and I will take some tomorrow. I just wont have a equal or close to equal samples of AA filter image, as part of my gear is in service.

[Phil Indeblanc]

It's kind of like giving a flawless diamond to your fiance'.  But 1/8th of a carat.  It's awesome to look at, but she's always wondering about the size.  Sometimes bigger and slightly less quality is better.  

Thats a rather good analogy, as "artifacts" and inclusions are sometimes not visible unless you use a microscope and a color index :-)  BUT there is a science that will define the stone as a VS1 or VVS1, and mark it as a second verses a Flawless...and worse yet, if you have one with much flourescence that is invisible to the naked eye, it will mark it down also.  Then color...hahaha...much indeed a good analogy.  :-)

[Theresa]

Ultimately, I would very much contemplate having the AA filter removed if it became possible to do that. To me, these clinical argument for the AA filter do not go along with real life and remind me very much of my doctor than can only prescrible high priced chemical medicines and balks if i suggest any natural alternatives. For him, there is only one way, but I know that is not true.

So i need to decide between "power files" of the sMK3 or the cleaner higher ISO and clearer pictures of the D3. I lean towards the sMK3 and the luminous sharpening in PK may tip the balance.

Peter

First of all a doctor (I am an RN) cannot or at least should not recommend "natural medicines" for which there is no scientific evidence regarding their efficacy.  Because they are marketed as "nutritional" they are not required to undergo testing, but they should be.   I think the idea of removing the AA filter is a good one for you, as you say AA doesn't bother you.  Different strokes for different folks.
Be careful not to poison yourself with toxic plants or AA though.

[joofa]

I think the idea of removing the AA filter is a good one for you, as you say AA doesn't bother you.  Different strokes for different folks.
Be careful not to poison yourself with toxic plants or AA though.

We build custom cameras for many medical imaging purposes such as fluorescence microscopy, etc. Many of our customers prefer not having an AA filter. As I have mentioned before this aliasing thingy is in the notice of engineers for at least 80 years. It is not a new thing and in natural images not a big deal as some camera manufacturers would like to make it who want to tout their superior pixel count. Several new and exciting technologies are going to hit the imaging world and I think it is about time if we find aliasing to be too objectionable to just use a camera which has an AA filter and move on.

[Bart_van_der_Wolf]

We build custom cameras for many medical imaging purposes such as fluorescence microscopy, etc. Many of our customers prefer not having an AA filter.

This by itself doesn't say much. If the subject matter has low contrast, and the optical chain functions as a low-pass filter, then adding an AA-filter would be overkill.

... I think it is about time if we find aliasing to be too objectionable to just use a camera which has an AA filter and move on.

And the majority of cameras do use an AA-filter (or an optical chain that functions as such). Some subject matter is not sensitive to aliasing artifacts, and some is. It's a matter of how are you going to cope with it when you get bitten by it. It's all a trade-off.

That being said, the losses of a sufficiently high resolution sampling with an optical low-pass filter are quite tolerable (and in part reversible by proper sharpening), and the amount of nasty surprises is reduced. Not a bad compromise I would say.

Cheers,
Bart

[joofa]

This by itself doesn't say much. If the subject matter has low contrast, and the optical chain functions as a low-pass filter, then adding an AA-filter would be overkill.

Hi, I am just saying that since, you, me, Daniel Browning, and countless others agree that aliasing is a subjective matter of appreciation then we are spending a disproportionate amount of time on its ill-effects.

[Phil Indeblanc]

That being said, the losses of a sufficiently high resolution sampling with an optical low-pass filter are quite tolerable (and in part reversible by proper sharpening), and the amount of nasty surprises is reduced. Not a bad compromise I would say.

Cheers,
Bart

NO, you cannot regain lost sharpening, you will only increase contrast, and preceived sharpness, no matter the channel, it is applying the same effect.
Some result better than others, but even with some samples posted here, you will see that you CANNOT regain the information that native sharpness resolved.