Pages: 1 2 [3] 4 5 ... 7   Go Down

Author Topic: AA-filtering CCD and CMOS  (Read 36582 times)

BernardLanguillier

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 12639
    • http://www.flickr.com/photos/bernardlanguillier/sets/
AA-filtering CCD and CMOS
« Reply #40 on: October 12, 2009, 08:24:03 am »

Quote from: jing q
and i would like to respond that there are people around who believe that the lack of AA filter HAS value.
and they aren't just leica users who need to justify their costs.

I want to believe in that, and wouldn't hesitate to have the AA filter of my d3x removed, but still haven't seen any samples proving the point.

Cheers,
Bernard

ErikKaffehr

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 11249
    • Echophoto
AA-filtering CCD and CMOS
« Reply #41 on: October 12, 2009, 12:58:41 pm »

Hi Bernard,

The question is really if removing the the AA-filter actually increases resolution or just reduces the need of sharpening. So the question is if we can just increase sharpening to compemsate for AA-filtering. It seems that if remove the AA-filter we will have same artifacts, colorful or not, but it seems no one cares about the artifacts as long as they are monochrome.

That helicopter picture of yours was impressive, how was it processed?

Best regards
Erik



Quote from: BernardLanguillier
I want to believe in that, and wouldn't hesitate to have the AA filter of my d3x removed, but still haven't seen any samples proving the point.

Cheers,
Bernard
Logged
Erik Kaffehr
 

aaykay

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 359
AA-filtering CCD and CMOS
« Reply #42 on: October 12, 2009, 02:24:59 pm »

Quote from: BernardLanguillier
I want to believe in that, and wouldn't hesitate to have the AA filter of my d3x removed, but still haven't seen any samples proving the point.

Cheers,
Bernard

I believe there was a company mentioned eariler, that removes AA filters for a charge, right ?  Would they not have before and after samples ?  What if we write to them or call them up ?
Logged

ErikKaffehr

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 11249
    • Echophoto
AA-filtering CCD and CMOS
« Reply #43 on: October 12, 2009, 02:39:39 pm »

Hi,

They have. Problem is that they are JPEG. I downloaded a couple of their samples and increased sharpening on the AA-filtered image and could not see a significant difference.

Here is my posting on the issue: http://luminous-landscape.com/forum/index....st&p=144346

and here is one from Christopher: http://luminous-landscape.com/forum/index....st&p=145485

Both have samples

Best regards
Erik

Quote from: aaykay
I believe there was a company mentioned eariler, that removes AA filters for a charge, right ?  Would they not have before and after samples ?  What if we write to them or call them up ?
« Last Edit: October 12, 2009, 02:57:51 pm by ErikKaffehr »
Logged
Erik Kaffehr
 

Plekto

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 551
AA-filtering CCD and CMOS
« Reply #44 on: October 12, 2009, 07:06:06 pm »

No AA filter in raw is always noticeable.   But you will get moires and jaggies unless you are using a Fuji or Foveon sensor or something without a Bayer pattern (or that technically does bracketing and blending in-camera)

Note - bracketing and blending half or even a quarter of a stop apart will make artifacts disappear.  It's a cheap and dirty method to get clean results if you are shooting something that isn't moving.  In this case, the AA filter isn't even needed.  But... finding a camera without one is essentially impossible these days as they cater to consumers instead of pros these days.
Logged

BernardLanguillier

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 12639
    • http://www.flickr.com/photos/bernardlanguillier/sets/
AA-filtering CCD and CMOS
« Reply #45 on: October 12, 2009, 07:06:42 pm »

Quote from: ErikKaffehr
That helicopter picture of yours was impressive, how was it processed?

Erik,

It was converted in C1 Pro with capture sharpening set at something like 400, 0.6 if I recall (my typical capture sharpening), works great on the d3x files at low ISO since there simply no noise from highlights to shadows.

I may have added a bit of sharpening in PS, not too sure what I did, but anyway this sample it representative of what I get with the d3x when using good lenses like the Zeiss 100mm f2.0 or the 300 f2.8 VR.

I keep thinking that it looks better when viewed at 100% than all the other AA filter less samples I have seen, excluding perhaps some of the P65+ samples.

Cheers,
Bernard

Daniel Browning

  • Full Member
  • ***
  • Offline Offline
  • Posts: 142
AA-filtering CCD and CMOS
« Reply #46 on: October 12, 2009, 07:38:49 pm »

George,

You made a post last week, but I didn't notice it until today.

Quote from: georgl
@Daniel Browning
The "look" of moire has definitely changed with the various sensor-generations (with increasing fill-rate) but alaising itself appears nevertheless and never seemed to influenced the choice of AA-filter vs. unfiltered!?

I don't understand if you're rephrasing my statement in the form of a question or making your own statement in the form of a comment, but perhaps it will help if I just add a clarification. My position is that aliasing characteristics are dependent on the optical fill factor (with microlenses considered), not the electronic fill factor (of the bare sensor with no microlenses). I think that microlenses have given CMOS optical fill factors comparable to CCD for at least several years; therefore it has not influenced the choice to use OLPF or not.

Quote from: georgl
AA-filters are needed if you have to avoid moire at any cost. Press-photographers usually don't have the time to post-process the images to remove moire - they rather live the loss of fine detail/contrast.

First of all, there is no post-processing that can truly remove moire. The best software (C1P IMHO) can only smear the moire into the surrounding detail.

Second, moire is only the worst and most offensive aliasing artifact. But there are many other aliasing artifacts that I find displeasing and unnatural, including jaggies, stair-stepping, sparkling, "snap to grid", wavy lines, bands, fringing, popping, strobing, noise, and false detail. These, too, are impossible to remove through any automated or semi-automated software process.

In real life, when you pour two liters of water into a one liter container, water spills out and makes a mess. But camera design is different: when you pour two liters of water into a one liter container, the water folds back on itself and corrupts the entire container. The amount of water is the level detail (spatial frequency), and the volume of the container is the number of megapixels in the camera. Aliasing is the corruption. Anti-aliasing filters reduce detail down to a level that can fit within the pixel resolution.

But of course, that's just me personally. Two people can look at the exact same image and each see something different. Take an aliased image for example. Where one sees overly harsh and sudden transitions from black to white in just 2 pixels, another sees microcontrast. Where one gets the impression of fakeness, another gets the feeling of sharpness. Where one is jarred by the conformation of small details into a slightly different location than they exist in nature, another is awestruck by the high acuity.

Same thing with anti-aliased images. Where one sees slow, smooth, and careful transitions from black to white, over 3 or more pixels, another sees mushy detail. One gets the impression of natural, life-like renditions, another gets the feeling of haze and low contrast.

So you may percieve an unfiltered image as having high microcontrast, sharpness, and acuity; while I see the same one as harsh and unnatural. The OLPF'd images you perceive as mushy, haze, lowcon images are, to me, smooth and natural. So it would be difficult for us to come to agreement on how big of an issue aliasing is.

I think part of the reason why some manufacturers (e.g. MFDB) exclude OLPF is cost. A good OLPF is lab-grown, high-grade, ground, and polished Lithium Niobate crystal. The cost scales exponentially with area because even the tiniest defect will show up on the image, thanks to being so close to the sensor. Even though MFDB is only three times more area than 35mm, the cost can be an order of magnitude (or more) higher. More importantly, Canon/Nikon ship millions of units a year, compared to less than 6,000/year for all MFDB combined, so economies of scale is a huge factor.

If camera manufacturers were shrewd enough, they would stop wasting so much money and effort to fight it. It's not like they get appreciated for it, they're more often lambasted (IMHO). I think the market of people that like aliasing is large enough. But since I happen to belong to the smaller part that prefers anti-aliased images, I'm glad they haven't (yet) given up on the expensive AA filters, and hope they never do. (At least until we start hitting diffraction cutoff frequencies at faster f-numbers.)

Quote from: georgl
But the basics of alaising and AA-filters remain unchanged, moire doesn't destroy detail and AA-filters don't preserve it.

I kindly disagree. For my taste, the AA-filtered image is better, because although the detail is low contrast, at least it's real. The detail in an unfiltered image is very high contrast, but it's false detail. But I understand that others have different personal preferences.
Logged
--Daniel

Plekto

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 551
AA-filtering CCD and CMOS
« Reply #47 on: October 12, 2009, 10:56:11 pm »

This last comment is important.  The reality is that high contrast(actual rather than artificial as you noted) and good definition is often of far more importance than absolute sharpness.
Logged

jing q

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 594
    • we are super
AA-filtering CCD and CMOS
« Reply #48 on: October 12, 2009, 11:31:06 pm »

Quote from: BernardLanguillier
I want to believe in that, and wouldn't hesitate to have the AA filter of my d3x removed, but still haven't seen any samples proving the point.

Cheers,
Bernard

I think if you were truly interested in that you would have seeked out some AA filterless images and tested it out yourself.
I'm not the only person who removed their AA filter however it's interesting to see a lot of people who don't use AA filterless cameras coming out of the woodworks to slam the idea of removing the AA filter everytime this topic is mentioned.

MR himself seems to like his images without AA filters, maybe these AA unfiltered images are not quite as terrible an idea as everyone makes them out to be?

just sayin' you know.
« Last Edit: October 13, 2009, 12:46:34 am by jing q »
Logged

jing q

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 594
    • we are super
AA-filtering CCD and CMOS
« Reply #49 on: October 13, 2009, 12:44:24 am »

Quote from: aaykay
I believe there was a company mentioned eariler, that removes AA filters for a charge, right ?  Would they not have before and after samples ?  What if we write to them or call them up ?

the company is Maxmax.
I think it is a good idea to call them up to post new samples, or maybe they should lend a few cameras to a few people to try out and give their opinion.
I guess marketing isn't their strong point.
Logged

BernardLanguillier

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 12639
    • http://www.flickr.com/photos/bernardlanguillier/sets/
AA-filtering CCD and CMOS
« Reply #50 on: October 13, 2009, 04:25:56 am »

Quote from: jing q
I think if you were truly interested in that you would have seeked out some AA filterless images and tested it out yourself.
I'm not the only person who removed their AA filter however it's interesting to see a lot of people who don't use AA filterless cameras coming out of the woodworks to slam the idea of removing the AA filter everytime this topic is mentioned.

I did look, and never liked what I saw, but I respect the opinion of those tho think/see different.

I have obviously not seen images from all possible cameras with/without AA filter, and I believe that the gain will vary from make to make, which is why I was interested in your samples.

Cheers,
Bernard



telyt

  • Guest
AA-filtering CCD and CMOS
« Reply #51 on: October 13, 2009, 07:58:13 am »

Show me the artifacts:





Both photos: Leica R8 with DMR digital back (10 MP, no AA filter), 280mm f/4 APO-Telyt-R

I don't see any artifacts in 16" x 24" prints.
« Last Edit: October 13, 2009, 09:01:24 am by telyt »
Logged

ejmartin

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 575
AA-filtering CCD and CMOS
« Reply #52 on: October 13, 2009, 08:18:16 am »

Quote from: telyt
Show me the artifacts:

http://www.wildlightphoto.com/birds/accipitridae/feha02.jpg

http://www.wildlightphoto.com/mammals/lagomorphs/btha04.jpg

Both photos: Leica R8 with DMR digital back (10 MP, no AA filter), 280mmm f/4 APO-Telyt-R

Hard to show any artifacts when they have been eliminated by downsampling.

Quote
I don't see any artifacts in 16" x 24" prints.

Do you know what you're looking for?
« Last Edit: October 13, 2009, 08:18:45 am by ejmartin »
Logged
emil

telyt

  • Guest
AA-filtering CCD and CMOS
« Reply #53 on: October 13, 2009, 08:41:54 am »

Quote from: ejmartin
Hard to show any artifacts when they have been eliminated by downsampling.

Buy a print and see for yourself.  Contact Appel Gallery in Sacramento.

Quote from: ejmartin
Do you know what you're looking for?

Yes I do.  So does the gallery owner.
Logged

michael

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 5084
AA-filtering CCD and CMOS
« Reply #54 on: October 13, 2009, 09:07:15 am »

I can't believe the amount of misinformation and disinformation that this topic has engendered.

Has the fact that every medium format back since Noah has not had an AA filter escaped anyone's notice? Do those that think that all or even most images taken without an AA have aliasing and artifacting think that the countless pros and highly critical photographers who use MF backs would tolerate this if it were true? Come on!

The reality is that aliasing is only visible in "some" images, and unless you shoot fabrics for a living, it's a very small number.

The advantage of not having an AA is clearly visible to anyone that has a good eye. In some cases it simply jumps out at you, image after image. In most cases its visible even in small prints and on screen as a type of increased clarity, as if a veil were lifted.

And as for sharpening compensating for having an AA, what are you thinking? Sharpening is about edge sharpness; AKA accutance. Removing an AA filter is about increasing resolution. Yes, adding USM increases apparent sharpness, but not real resolution. Two different things, though related in the real world.

Bumble bees can fly, though aeronautical engineers used to say that it was impossible. They just didn't bother asking the bees. And yes, removing the AA filter on a properly designed system does increase both real and apparent resolution. Talk to the engineers that design these systems, and also just trust your own eyes.

And as for removing moire in software don't be too sure it can't be done. I'm working with one company now that is likely to have something exciting in this area in the months ahead.  

Michael
Logged

telyt

  • Guest
AA-filtering CCD and CMOS
« Reply #55 on: October 13, 2009, 09:24:51 am »

Quote from: Daniel Browning
For my taste, the AA-filtered image is better, because although the detail is low contrast, at least it's real.

Nonsense.  Almost nothing in a photograph is real.  All that matters is that it's believable.

Common artifacts we take for granted:

film grain
digital noise
2-dimesions
limited DOF
a moment in time
limited field of view
lens aberations

AA blurring is an artifact too.  Pick the one(s) you're willing to live with
« Last Edit: October 13, 2009, 10:07:15 pm by telyt »
Logged

thierrylegros396

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1800
AA-filtering CCD and CMOS
« Reply #56 on: October 13, 2009, 09:40:43 am »

Quote from: michael
And as for sharpening compensating for having an AA, what are you thinking? Sharpening is about edge sharpness; AKA accutance. Removing an AA filter is about increasing resolution. Yes, adding USM increases apparent sharpness, but not real resolution. Two different things, though related in the real world.

just trust your own eyes.

Michael

For those who have knowledge in signal transmission, sharpening can be compared to equalization used in high speed data line to recover the signal !

It's not perfect, but it works.

So yes, the result is the only real important thing !

But in some very rare instance, aliasing cannot be eliminated.

In real world however, bandwidth is limited enough by the lens.

Have a Nice Day !

Thierry
Logged

ejmartin

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 575
AA-filtering CCD and CMOS
« Reply #57 on: October 13, 2009, 10:52:28 am »

Quote from: michael
I can't believe the amount of misinformation and disinformation that this topic has engendered.

I think what you're seeing is two groups of people talking past one another.  One group understands the technical aspects of signal processing, and what aliasing is in a precise quantitative sense; another group has a rough idea of what aliasing is in terms of a set of experiences and examples of converted RAW images.  

It's a bit like the use of the term "dynamic range".  There is a precise engineering definition of DR (max signal divided by noise without signal), and a working photographer's definition of DR (max range of signal with 'acceptable' S/N ratio).  The difference between the two (the working photographer's version is typically several stops lower) causes endless heated 'discussions'.

I don't want to derail this thread into a foodfight on DR, I merely brought it up as another instance where different usages of the same terminology lead to each side misunderstanding the other's point of view.

Quote
Has the fact that every medium format back since Noah has not had an AA filter escaped anyone's notice? Do those that think that all or even most images taken without an AA have aliasing and artifacting think that the countless pros and highly critical photographers who use MF backs would tolerate this if it were true? Come on!

The reality is that aliasing is only visible in "some" images, and unless you shoot fabrics for a living, it's a very small number.

The advantage of not having an AA is clearly visible to anyone that has a good eye. In some cases it simply jumps out at you, image after image. In most cases its visible even in small prints and on screen as a type of increased clarity, as if a veil were lifted.

Actually, all that "pop" and "sizzle" of sharp edges in converted images from an AA-less camera is largely aliasing.  Aliasing is not just moire.

What the "signal processing camp" is saying is that, in terms of fidelity to the scene being imaged, a properly processed image from a sensor with an AA filter yields a more faithful digitization of the scene being captured than the same scene captured with a sensor without an AA filter.

Now, it may be that accurate image capture is not the goal; many people like all the pop and sizzle that aliasing provides, just as many people prefer oversaturated images.  What the "end user" camp is saying is that they like the effect of aliasing, so long as it doesn't manifest itself in forms objectionable to them such as moire.

Quote
And as for sharpening compensating for having an AA, what are you thinking? Sharpening is about edge sharpness; AKA accutance. Removing an AA filter is about increasing resolution. Yes, adding USM increases apparent sharpness, but not real resolution. Two different things, though related in the real world.

The DPReview report on the DP2 provides a good example of the increased "resolution" provided by the lack of an AA filter:

http://www.dpreview.com/reviews/sigmadp2/page22.asp

Count the number of lines at one end of the DP2 resolution pattern and compare it to the other end, for any orientation.  The pattern looks nice and sharp, and if you were just to look at the pattern from say 22 to 24 on the chart you would say that the camera is resolving all the way out to the limit of the chart.  But actually it is just aliasing a more finely spaced set of lines into a more coarsely spaced set of lines; it is not actually resolving at that level.  Aliasing definitely helps the accutance though  
« Last Edit: October 13, 2009, 11:18:55 am by ejmartin »
Logged
emil

BJL

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 6425
AA-filtering CCD and CMOS
« Reply #58 on: October 13, 2009, 11:18:26 am »

Michael, I agree with most of what you say about the pros and cons of AA filters (in a nutshell I would say that the higher the pixel count, the better the argument for omitting the AA filter)

But I have to object to yet another statement of the following modern myth, which is an insult to many of my scientific friends and colleagues who work in the area of aerodynamics:
Quote from: michael
Bumble bees can fly, though aeronautical engineers used to say that it was impossible.
Actually what the aeronautical engineer said is completely true and very useful information, which sadly has been corrupted into an anti-scientific myth, often trotted out when people wish to dismiss scientific conclusions that they do not wish to accept.

What was discovered was that a bee would not be able to fly, if its wings were rigid, instead of flexing during flight as they in fact do. The flexing of a bee's wings during flight adds significantly to their propulsional effectiveness. This is good science; both true (experimentally confirmed) and useful: for example it is relevant to the design of helicopter rotors, making use of flexibility.


I have to wonder about the many people who believe this myth of the incompetence of aeronautical engineers ... and yet happily fly in aircraft that those "incompetents" help to design!
« Last Edit: October 13, 2009, 11:19:05 am by BJL »
Logged

thierrylegros396

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1800
AA-filtering CCD and CMOS
« Reply #59 on: October 13, 2009, 01:12:57 pm »

Same problem occurs with digital audio !

Do you prefer sharp edge high frequencies from your tweeters or softer ones ?!

But the problem is more important when you have clipping !

The sound can become really crappy.

Link to The Nyquist Theorem tells us that we can successfully sample and play back frequency components up to one-half the sampling frequency.

Have a Nice Day.

Thierry
« Last Edit: October 13, 2009, 01:14:58 pm by thierrylegros396 »
Logged
Pages: 1 2 [3] 4 5 ... 7   Go Up