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Math question - sort of



 
 
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  #31  
Old September 28th 09, 07:58 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Alan Browne
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Posts: 12,640
Default Math question - sort of

John Navas wrote:
On Sun, 27 Sep 2009 21:02:51 -0400, Alan Browne
wrote in
:

You Are The Weakest Link wrote:
On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne
wrote:

John Sheehy wrote:
John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml

Sensors for larger formats are approaching the diffraction limit of
real lenses, and it is more difficult to get high levels of
aberration suppression for them. The point is that you cannot fully
exploit the resolution potential of high-resolution sensors with
regular mass-produced lenses, particularly for larger formats.
The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.
Is that another way of saying the Kodak empirical formula for end image
resolution (on film) is...

1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ?

So increasing either the sensor density or the lens resolution results
in higher output resolution, though of course with diminishing returns.
It's not an "either/or" venture. It's an "and" issue.

You really don't know how to read and understand that "increasing
either" also includes "increasing both" do you?


You manufacture resolution. You are always limited by the resolution of
the lens. Increasing resolution of the sensor past that point just
copies lens artifacts more faithfully.


It's not a choke and it's not that simple - that is where the empirical
formula from Kodak comes from. To be sure, the returns are diminishing
on both sides.
  #32  
Old September 29th 09, 12:40 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Wolfgang Weisselberg
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Posts: 5,285
Default Math question - sort of

You Are The Weakest Link wrote:
On Sun, 27 Sep 2009 21:02:51 -0400, Alan Browne


You really don't know how to read and understand that "increasing
either" also includes "increasing both" do you?


You don't know how to comprehend that increasing either does NOT include
increasing both.


OR != XOR. Look it up. Write a logic table.

-Wolfgang
  #33  
Old October 7th 09, 02:59 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
John Sheehy
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Default Math question - sort of

John Navas wrote in
news
On Mon, 28 Sep 2009 00:27:28 GMT, John Sheehy wrote in
:


I meant the density itself. Of course, microlenses could be poorly
designed. Even then, however, oversampling allows extemely easy and
smooth correction of CA, both from the lens, and that generated by
poor microlenses.


Oversampling does not facilitate correction of CA


Yes, it does. You lose all your eggs when you put them in big pixels and
have to shift them by non-integer numbers of pixels.

or microlens
aberrations.


That's all in the design - a microlens doesn't have to cause any CA-like
effects of its own.
  #34  
Old October 7th 09, 09:48 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
John Sheehy
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Default Math question - sort of

John Navas wrote in
:

On Tue, 06 Oct 2009 20:59:01 -0500, John Sheehy wrote in
:


John Navas wrote in
news


Oversampling does not facilitate correction of CA


Yes, it does. You lose all your eggs when you put them in big pixels
and have to shift them by non-integer numbers of pixels.


Not so.


So what do you do, use point-sampling and wind up with a nearest-neighbor
jaggy mess?

  #35  
Old October 7th 09, 10:14 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Martin Brown
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Posts: 821
Default Math question - sort of

John Sheehy wrote:
John Navas wrote in
:

On Tue, 06 Oct 2009 20:59:01 -0500, John Sheehy wrote in
:


John Navas wrote in
news


Oversampling does not facilitate correction of CA


Yes, it does. You lose all your eggs when you put them in big pixels
and have to shift them by non-integer numbers of pixels.


Not so.


Although it does make it easier.

So what do you do, use point-sampling and wind up with a nearest-neighbor
jaggy mess?


There are resampling methods derived from radio astronomy that can
handle this situation accurately but they are computationally expensive.
Bilinear spline is about the cheapest half decent option found in
standard packages. But there are better ones if you have resources to
burn. It ends up with the law of diminishing returns so how far you push
it is really determined by how unique or irreplaceable the image is.

If you have the option then oversampling the measured data by about 1.5x
the Nyquist theoretical minimum for a monochrome imaging system is
worthwhile. Otherwise you may see obvious jaggies in the raw image.
Beyond that you are not gaining much although for a Bayer sensor you
still get a bit of extra chroma information out to 2x oversampled.

Regards,
Martin Brown
  #36  
Old October 8th 09, 08:45 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Martin Brown
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Posts: 821
Default Math question - sort of

John Navas wrote:
On Wed, 07 Oct 2009 22:14:35 +0100, Martin Brown
wrote in
:

There are resampling methods derived from radio astronomy that can
handle this situation accurately but they are computationally expensive.
Bilinear spline is about the cheapest half decent option found in
standard packages. But there are better ones if you have resources to
burn. It ends up with the law of diminishing returns so how far you push
it is really determined by how unique or irreplaceable the image is.

If you have the option then oversampling the measured data by about 1.5x
the Nyquist theoretical minimum for a monochrome imaging system is
worthwhile. Otherwise you may see obvious jaggies in the raw image.
Beyond that you are not gaining much although for a Bayer sensor you
still get a bit of extra chroma information out to 2x oversampled.


There's a big difference between sampling the same signal multiple times
(time) and breaking up a photosite into multiple photosites (area).


Actually there isn't all that much of a difference apart from the
obvious one that a time series is one dimensional and so a lot more
amenable to analytical techniques when sampled at equal intervals.

Time sampled data is usually integrated over a time delta-t rather than
a true snapshot of the signal by a flash converter at exact time t.

If, for example, you have a single point photosite at or above the
resolution limit of the lens, and you divide it into four photosites,
you are not adding resolution (limited by the lens), you are at most
more accurately sampling the luminosity of that point, depending on the
tradeoff between photosite size (sensitivity) and the noise floor.


Indeed, but having some of that extra data can make post processing
deconvolution more reliable provided that you have not traded signal to
noise.

The point here is that an undersampled digital image does present some
difficulties for post processing to remove chromatic and other
abberations. They are not insurmountable but it is easier with an
oversampled image.

Regards,
Martin Brown
  #37  
Old October 9th 09, 04:48 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Mr. Strat
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Posts: 1,089
Default Math question - sort of

In article , John Navas
wrote:

Theory is interesting, but in the real world it's just not an issue --
Panasonic has long been correcting CA with in-camera processing and
without oversampling, and the result is excellent (not a
"nearest-neighbor jaggy mess").


Are you still using that Panasonic piece of ****? I guess it doesn't
matter since you don't have the ability to create a decent image.
  #38  
Old October 9th 09, 03:33 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
George Kerby
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Posts: 4,798
Default Math question - sort of




On 10/8/09 10:48 PM, in article ,
"Mr. Strat" wrote:

In article , John Navas
wrote:

Theory is interesting, but in the real world it's just not an issue --
Panasonic has long been correcting CA with in-camera processing and
without oversampling, and the result is excellent (not a
"nearest-neighbor jaggy mess").


Are you still using that Panasonic piece of ****? I guess it doesn't
matter since you don't have the ability to create a decent image.


And he's still using the Motorola phone charger...

 




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