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08-09-2011, 10:48 PM   #31
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QuoteOriginally posted by robgo2 Quote
No AA filter = color moire. Why do you consider this a good thing, especially when it is so simple to counter AA filter softness with capture sharpening? I just don't understand this aversion to AA filters. Manufacturers use them for a good reason, not because they want to irritate users who think that they cannot get sharp images with those damn filters in the way.
The same can be said for the opposite: why put the antialiasing filter, when you can blur the picture later in post production, to avoid moire?

08-10-2011, 02:09 AM   #32
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QuoteOriginally posted by eurostar Quote
The same can be said for the opposite: why put the antialiasing filter, when you can blur the picture later in post production, to avoid moire?
How do you do that? (Serious question, I quite often get moire with the weak AA filter of my K10D)
08-10-2011, 06:17 AM   #33
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QuoteOriginally posted by eurostar Quote
The same can be said for the opposite: why put the antialiasing filter, when you can blur the picture later in post production, to avoid moire?
QuoteOriginally posted by gazonk Quote
How do you do that? (Serious question, I quite often get moire with the weak AA filter of my K10D)
By not understanding signal theory. It is not possible to suppress aliasing (caused by subsampling spacial frequencies) with signal processing. It is possible to attenuate the effects somehow in controlled situation but there is no guaranty.

The AA filter + sharpening makes actually a lot of sense when you know a little bit of signal processing theory. However, knowing what is acceptable for real life situations another thing. Another thing as well is Pixel peeping and marketing. Pentax had plans to release the 645D with an AA filter, but since MF user were used to work without it, they released the camera without any AA filter.
08-11-2011, 03:18 AM   #34
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QuoteOriginally posted by ghelary Quote
The AA filter + sharpening makes actually a lot of sense when you know a little bit of signal processing theory.
+1

You absolutely need AA with a Bayer sensor or you may end up with ruined shots.

However, a soft lens (e.g., wide open), mild defocus, a very small aperture, some shake or some motion blur will all provide some AA. The more the smaller the pixel pitch. Most in need of an AA filter is a 6MP camera in the studio. Least in need is a 18MP camera used for sports.

Therefore, a static AA filter (incl. none at all) doesn't fit everybody.

Therefore, the ideal AA filter would be an unaudible ultrasonic 40kHz sensor vibration overlaid using the SR module which is (or could be) strong enough to do this. The amplitude would be controlled by the shooting situation (flash, shutter, lens, aperture etc.). Moreover, it would get rid of the nasty aliasing artefacts in video mode where the AA filter has no effect (flickering lines and edges).

Pentax really should file a patent for this application of their SR mechanism.


Personally, I prefer a weak AA filter. Not a strong one and not a missing one.

08-11-2011, 03:55 AM   #35
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QuoteOriginally posted by falconeye Quote
+1

You absolutely need AA with a Bayer sensor or you may end up with ruined shots.

However, a soft lens (e.g., wide open), mild defocus, a very small aperture, some shake or some motion blur will all provide some AA. The more the smaller the pixel pitch. Most in need of an AA filter is a 6MP camera in the studio. Least in need is a 18MP camera used for sports.

Therefore, a static AA filter (incl. none at all) doesn't fit everybody.

Therefore, the ideal AA filter would be an unaudible ultrasonic 40kHz sensor vibration overlaid using the SR module which is (or could be) strong enough to do this. The amplitude would be controlled by the shooting situation (flash, shutter, lens, aperture etc.). Moreover, it would get rid of the nasty aliasing artefacts in video mode where the AA filter has no effect (flickering lines and edges).

Pentax really should file a patent for this application of their SR mechanism.


Personally, I prefer a weak AA filter. Not a strong one and not a missing one.
Yeah, I didn't go into this level of detail because that when people start confusing things.
- Current AA filters are not very performant filter compared to other domain like sound for example. So a strong AA filter will suppress a lot of spacial frequencies that could be captured by the sensor. And a weak AA filter leave remaining aliasing issues
- Pixel are not dots, the form and the surface of the sensitive area of the pixel (relative the non sensitive area) will act as a low pass filter.
- You're right in saying that a bayer matrix will have more problem than a monochrome pattern (or Sigma's Foveon) for the same reason as above.
The more there is separation between color channels (color accuracy) the more accute the problem will be.
- Aliasing is caused by the high spatial frequencies of the image projected on the sensor. So it is true that the aliasing can be suppressed by "blurring" the lens (mis-focus, low resolution lens, diffraction limited) I believe this is also one of the reasons why MF cameras have no AA filter, good MF lenses have less microcontrast than good 35mm lenses. They have more accross the image, but at pixel level they have less.

The "40kHz sensor vibration overlaid" is a brilliant idea IMO, but lots of good idea don't go past the lab because of implementation issues. But sure some tunnable AA filter would be great for shooting depending on the subject.

Just on a side note, no "great picture" in the history of photography were great because of sharpness. Early Cartier-Bresson work had poor resolution (I've seen orginal prints in exhibits) even by cameraphone standard. Ansel Adams was part of the group F64 (yeah shooting at F64) and you can guess he wasn't being really much concerned about diffraction limitations.
On the other side the false patterns created by aliasing can completly ruin a shot by being distracting.
08-11-2011, 05:47 AM   #36
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QuoteOriginally posted by ghelary Quote
Just on a side note, no "great picture" in the history of photography were great because of sharpness. Early Cartier-Bresson work had poor resolution (I've seen orginal prints in exhibits) even by cameraphone standard. Ansel Adams was part of the group F64 (yeah shooting at F64) and you can guess he wasn't being really much concerned about diffraction limitations.
Thanks to you and Falconeye for a brief education on AA. I would presume that the folks at Ricoh have thought this through and determined that there is more benefit to not having the AA filter on this module than having one.

And great side note!
08-11-2011, 06:44 AM   #37
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QuoteOriginally posted by ghelary Quote
Ansel Adams was part of the group F64 (yeah shooting at F64) and you can guess he wasn't being really much concerned about diffraction limitations.
F/64 on a 4x5 format translates to f/11 on 35mm (FF). Doesn't sound as insane anymore.
08-11-2011, 06:48 AM   #38
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QuoteOriginally posted by johnmflores Quote
I would presume that the folks at Ricoh have thought this through and determined that there is more benefit to not having the AA filter on this module than having one.
It is a potential advantage of "lensors" (lens/sensor modules) that you can match lens and sensor. The lens itself can be the low-pass filter; no need for an AA filter anymore.

This can be achieved by making the sensor highly resolving or the lens not sharper than required for the sensor. I don't know if Ricoh used either approach in the above case, but it is certainly a possibility.

08-11-2011, 06:53 AM   #39
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QuoteOriginally posted by Class A Quote
F/64 on a 4x5 format translates to f/11 on 35mm (FF). Doesn't sound as insane anymore.
Even less insane when you realise Ansel shot a large number of his images on 8x10 so it was even less of an issue
08-11-2011, 07:40 AM   #40
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QuoteOriginally posted by eddie1960 Quote
Even less insane when you realise Ansel shot a large number of his images on 8x10 so it was even less of an issue
Then f/64 translates to f/8...
08-11-2011, 11:38 AM   #41
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QuoteOriginally posted by johnmflores Quote
I would presume that the folks at Ricoh have thought this through
That sort of things is decided in management (Dilbert-style) meetings.

And therefore we know that the relevant and only question asked was what Leica does in the M8/M9 cameras ...
08-11-2011, 05:36 PM   #42
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QuoteOriginally posted by Class A Quote
F/64 on a 4x5 format translates to f/11 on 35mm (FF). Doesn't sound as insane anymore.
and if you will see what PL25/1.4 does @ f11 on 2x crop



then f/11 on FF is just a matter of lens quality (which costs money, yes).
08-11-2011, 08:19 PM   #43
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QuoteOriginally posted by johnmflores Quote
No AA hasn't hurt sales of Leica's M9...
Come on, now. Leica is a world unto itself. We could spend weeks analyzing the buying habits of Leica users and their motivations. No doubt, the M9 is a great camera, but not because it lacks an AA filter. I'm sure that there are many occasions when users are pulling their hair out trying to correct moire. Falk Lumo has written on the subject of AA filters in these pages. You can look it up.

Rob
08-12-2011, 11:45 AM   #44
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QuoteOriginally posted by robgo2 Quote
I'm sure that there are many occasions when users are pulling their hair out trying to correct moire.
nope, they will just postprocess to B&W... that helps

plus we do not hear a lot of screaming from MF(DB) users w/ 20-40mp AA-less sensors, pretty much same sensel-density

Last edited by deejjjaaaa; 08-12-2011 at 08:21 PM.
08-12-2011, 01:02 PM   #45
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QuoteOriginally posted by deejjjaaaa Quote
plus we do not hear a lot of screaming from MF(DB) users w/ 20-40mp AA lens sensors, pretty much same sensel-density
May be true or not.

I've seen in an early hands-on report (from Japan) about the 645D some questioning why window structures in the distance had color seams. It looked ugly enough for him to raise the question in his blog. From the test shots, it clearly was color moire from the missing AA filter. And in the particular case, the pattern was irregular enough to avoid a problem for the overall picture.

So, the tester observed a problem with the missing AA filter but didn't recognize it as such. I imagine this is the norm in the MF camp. Measurebators don't shoot MF
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