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Re: Smartphone heavy moiré

 
 
David J Taylor
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      10-22-2011
> Samsung Galaxy S2, look at the jacket:
> http://www.molon.de/S2/P5.jpg
>
> Apparently Samsung forgot to put an AA filter into the camera module.
> --
>
> Alfred Molon


It will be built down to a price, Alfred, and the typical,
photographically uneducated, customer may prefer "sharp" to "anti-alias".

Thanks for posting, though. Proves the lens isn't too bad, I suppose!

Cheers,
David

 
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Apteryx
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      10-22-2011
On 23/10/2011 3:51 a.m., David J Taylor wrote:
>> Samsung Galaxy S2, look at the jacket:
>> http://www.molon.de/S2/P5.jpg
>>
>> Apparently Samsung forgot to put an AA filter into the camera module.
>> --
>>
>> Alfred Molon

>
> It will be built down to a price, Alfred, and the typical,
> photographically uneducated, customer may prefer "sharp" to "anti-alias".


Let 'em buy Leicas

Apteryx
 
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Bruce
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      10-22-2011
Apteryx <(E-Mail Removed)> wrote:
>On 23/10/2011 3:51 a.m., David J Taylor wrote:
>>> Samsung Galaxy S2, look at the jacket:
>>> http://www.molon.de/S2/P5.jpg
>>>
>>> Apparently Samsung forgot to put an AA filter into the camera module.
>>> --
>>>
>>> Alfred Molon

>>
>> It will be built down to a price, Alfred, and the typical,
>> photographically uneducated, customer may prefer "sharp" to "anti-alias".

>
>Let 'em buy Leicas



In truth, it is the typical, photographically uneducated consumer who
prefers the mushy result of a strong anti-alias (AA) filter which is
then artificially sharpened, allegedly to resemble the original
unmushed image. Of course any resemblance is purely a coincidence.

To those who are photographically educated, shooting images that are
sharp straight out of the camera without an AA filter is a fulfilling
experience. It is a heck of a lot more fulfilling than shooting mushy
images that are artificially sharpened.

That's why Hasselblad, Leica and other medium format digital cameras
don't have AA filters, and the Leica M8 and M9 too. Ask anyone who
actually uses these cameras about the alleged "problems" of moire and
aliasing and they will laugh in your face.

Moire is alleged - by those who don't know any better - to be a
particular problem in fashion photography. But absolutely every
fashion photographer I know who uses digital equipment uses cameras
that don't have AA filters. Similarly, aliasing is alleged - by the
very same people - to be a particular problem in architectural
photography. But architectural photographers also tend to use cameras
that don't have AA filters.

Why throw away the ability to resolve fine detail because of two
non-problems that exist only as a theory in the minds of the ignorant
and uneducated? In practice, moire and aliasing are as rare as they
are easily dealt with.

 
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nospam
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Posts: n/a
 
      10-23-2011
In article <(E-Mail Removed)>, Bruce
<(E-Mail Removed)> wrote:

> In truth, it is the typical, photographically uneducated consumer who
> prefers the mushy result of a strong anti-alias (AA) filter which is
> then artificially sharpened, allegedly to resemble the original
> unmushed image. Of course any resemblance is purely a coincidence.
>
> To those who are photographically educated, shooting images that are
> sharp straight out of the camera without an AA filter is a fulfilling
> experience. It is a heck of a lot more fulfilling than shooting mushy
> images that are artificially sharpened.


bullshit, and actually the opposite is correct.

those who are educated, particularly with regards to what aliasing
actually is know that the only way to guarantee a resemblance to the
subject is with an anti-alias filter.

without an anti-alias filter, you get alias artifacts, which is *false*
detail, but some people apparently think it looks good. on occasion it
can but there's no way to know that ahead of time. usually, aliasing
causes ugly artifacts, particularly when it's low frequency.

> That's why Hasselblad, Leica and other medium format digital cameras
> don't have AA filters, and the Leica M8 and M9 too. Ask anyone who
> actually uses these cameras about the alleged "problems" of moire and
> aliasing and they will laugh in your face.


no, it's because aa filters large enough for a medium format sensor are
very expensive and the camera already has enough resolution for it to
not matter in most cases. the lens becomes the limiting factor.

> Moire is alleged - by those who don't know any better - to be a
> particular problem in fashion photography. But absolutely every
> fashion photographer I know who uses digital equipment uses cameras
> that don't have AA filters.


how many do you know? not a single one uses a d3x or 1ds?

> Similarly, aliasing is alleged - by the
> very same people - to be a particular problem in architectural
> photography. But architectural photographers also tend to use cameras
> that don't have AA filters.


actually, most use cameras that do have an aa filter, regardless of
subject. the only cameras that lack an aa filter are cameras that don't
sell in high quantities (that should tell you something right there).

> Why throw away the ability to resolve fine detail because of two
> non-problems that exist only as a theory in the minds of the ignorant
> and uneducated?


an anti-alias filter does not throw away detail, it limits detail that
is beyond what the sensor can resolve.

> In practice, moire and aliasing are as rare as they
> are easily dealt with.


not after it's captured it isn't.
 
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David J Taylor
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      10-23-2011
"Alfred Molon" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ...
> In article <231020110223481505%(E-Mail Removed)>, nospam says...
>> an anti-alias filter does not throw away detail, it limits detail that
>> is beyond what the sensor can resolve.

>
> AA filters are indeed necessary to get rid of detail beyond the Nyquist
> limit, it's just that with digital cameras there are two problems:
>
> 1. In a Bayer sensor the colour resolution is much lower than the
> luminance resolution, so I'm guessing that the AA filter is dimensioned
> to block somewhere between the colour and the luminance resolution, in
> an effort to maximise the detail and keep aliasing not too high. This is
> one of the reasons why Bayer sensors suck.


Yes, it will be a compromise setting, and different cameras have different
compromises, different between manufacturers, and different between
different cameras in the same manufacturer's range. For most people, the
compromises of the Bayer sensor are preferable to those of the Foveon
sensor, otherwise far more people would buy the latter.

If someone prefers to see the aliasing artefacts, then they can buy a
camera with a weaker AA filter. Their choice, but the images will be less
accurate. For advertising, perhaps image accuracy is less important! <G>

> 2. I suspect that these AA filters are not too terribly efficient.
> Probably a soft slope curve, rather than a rectangle response (i.e. 100%
> until the limit, then 0).
> --
>
> Alfred Molon


Yes, IIRC it's approximately rectangular in the spatial domain, rather
than in the spatial frequency domain. Unlike audio anti-alias filters,
it's much more difficult to make optical anti-alias filters with a sharp
cut-off response.

Just as with over-sampled filters in audio making the smoother cut-off
more acceptable, it may be that optically having a higher sensor density
(much nearer to the lens cut-off spatial frequency) effectively
over-sampling the image may produce better results, other things being
equal. Of course, other things are never equal!

Cheers,
David

 
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nospam
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      10-23-2011
In article <(E-Mail Removed)>, Alfred
Molon <(E-Mail Removed)> wrote:

> > an anti-alias filter does not throw away detail, it limits detail that
> > is beyond what the sensor can resolve.

>
> AA filters are indeed necessary to get rid of detail beyond the Nyquist
> limit, it's just that with digital cameras there are two problems:
>
> 1. In a Bayer sensor the colour resolution is much lower than the
> luminance resolution, so I'm guessing that the AA filter is dimensioned
> to block somewhere between the colour and the luminance resolution, in
> an effort to maximise the detail and keep aliasing not too high. This is
> one of the reasons why Bayer sensors suck.


bayer sensors do not suck and their colour resolution is not 'much
lower,' it's half of luminance and substantially more than what human
eyes can resolve. it's actually an extremely clever design.

> 2. I suspect that these AA filters are not too terribly efficient.
> Probably a soft slope curve, rather than a rectangle response (i.e. 100%
> until the limit, then 0).


it's not possible for a sharp cutoff.
 
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Bruce
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      10-23-2011
"David J Taylor" <(E-Mail Removed)> wrote:
>For most people, the
>compromises of the Bayer sensor are preferable to those of the Foveon
>sensor, otherwise far more people would buy the latter.



There are other reasons in play here. The main one being that to buy
Foveon, you have to buy a Sigma DSLR, and that limits you to using
Sigma lenses. Now some people won't mind that, but whether the same
people are prepared to pay the price of a Sigma SD1 is moot.

On the subject of AA filters, Nikon has gradually made theirs more
subtle over the last few years. I think we may be at the point where
the next generation of Nikon pro DSLRs may have AA filters only as an
option. I base this on the fact that at least some of the test
versions of the new Nikon models have no AA filter.



 
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David J Taylor
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      10-23-2011
"Bruce" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> "David J Taylor" <(E-Mail Removed)> wrote:
>>For most people, the
>>compromises of the Bayer sensor are preferable to those of the Foveon
>>sensor, otherwise far more people would buy the latter.

>
>
> There are other reasons in play here. The main one being that to buy
> Foveon, you have to buy a Sigma DSLR, and that limits you to using
> Sigma lenses. Now some people won't mind that, but whether the same
> people are prepared to pay the price of a Sigma SD1 is moot.


To a degree, yes, but if Foveon were that good then would not the other
camera manufacturers would have adopted it as well?

> On the subject of AA filters, Nikon has gradually made theirs more
> subtle over the last few years. I think we may be at the point where
> the next generation of Nikon pro DSLRs may have AA filters only as an
> option. I base this on the fact that at least some of the test
> versions of the new Nikon models have no AA filter.


If there are no components from the lens at higher than half the sampling
frequency, then no AA filter is needed. This is oversampling in the
optical domain just like oversampling in audio, which is widely practiced.
Hence if the pixel count is very high, in simple terms the sensor is
"better" than the lens (a higher resolution) and hence no AA filter is
required (or it's less important, or it can be made weaker). This breaks
down, though, if you then put a super-high resolution lens on such a
system....

When you have a relatively small number of pixels, an AA filter is
required to prevent aliasing and the unpleasant artefact it produces.

Cheers,
David

 
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Bruce
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      10-23-2011
"David J Taylor" <(E-Mail Removed)> wrote:
>"Bruce" <(E-Mail Removed)> wrote in message
>news:(E-Mail Removed).. .
>> "David J Taylor" <(E-Mail Removed)> wrote:
>>>For most people, the
>>>compromises of the Bayer sensor are preferable to those of the Foveon
>>>sensor, otherwise far more people would buy the latter.

>>
>>
>> There are other reasons in play here. The main one being that to buy
>> Foveon, you have to buy a Sigma DSLR, and that limits you to using
>> Sigma lenses. Now some people won't mind that, but whether the same
>> people are prepared to pay the price of a Sigma SD1 is moot.

>
>To a degree, yes, but if Foveon were that good then would not the other
>camera manufacturers would have adopted it as well?



Hasselblad went a very long way down the road with Foveon before
finally giving up and choosing conventional CCD sensors. The
agreement with Hasselblad was exclusive, so that prevented any other
manufacturer using a Foveon sensor.

By the time Hasselblad opted for Bayer-pattern CCD, the other
manufacturers has already made their own arrangements for sensor
supply. So Foveon struggled on alone until eventually finding a
customer in Sigma.

Eventually, after being Foveon's sole customer for several years,
Sigma bought the Foveon company. I would not be surprised if camera
manufacturers were unhappy about selling their sensors to a company
that, as a lens manufacturer, had reverse engineered their own
lens/camera interfaces and offered low cost lenses that undercut their
own camera brand products. So why would they sell their sensors to
Sigma and enable that company to offer low cost DSLRs that undercut
their own ranges?

So Sigma and Foveon needed each other. But if Foveon's survival now
depends on sales of Sigma's SD1 ... ?

 
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nospam
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      10-23-2011
In article <(E-Mail Removed)>, Bruce
<(E-Mail Removed)> wrote:

> On the subject of AA filters, Nikon has gradually made theirs more
> subtle over the last few years. I think we may be at the point where
> the next generation of Nikon pro DSLRs may have AA filters only as an
> option. I base this on the fact that at least some of the test
> versions of the new Nikon models have no AA filter.


they're weaker because the sensor's resolution is higher. at some point
the lens becomes the aa filter. further evidence that many people don't
understand what an aa filter is actually for.
 
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