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Author Topic: removing the AA filter  (Read 66578 times)
ErikKaffehr
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« Reply #160 on: January 11, 2010, 11:28:08 PM »
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Hi,

I have downloaded and had a look. Don't know what to say...

I don't see artifacts jumping at me.

Best regards
Erik


Quote from: Phil Indeblanc
This is the longest pause this post has had...anyone DL the image and look it over?
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Phil Indeblanc
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« Reply #161 on: January 12, 2010, 02:06:34 AM »
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Quote from: ErikKaffehr
Hi,

I have downloaded and had a look. Don't know what to say...

I don't see artifacts jumping at me.

Best regards
Erik


Perhaps they are not jumping...Are there any artifacts like we have been discussing?..maybe point a couple things out?
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Daniel Browning
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« Reply #162 on: January 12, 2010, 04:08:32 AM »
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I converted it to DNG. Here it is for anyone else who wants it for convenience: FM9R3347.dng.

Quote from: Phil Indeblanc
...anyone DL the image and look it over?

I have a few observations. Most of the image is outside the plane of critical focus, including the entire leaf and much of the ruler. The thin DOF (around one inch in this photo) precludes aliasing. The sharpness is not as high as I would expect for an aliasing test. None of the subjects provide sufficiently fine details (at high contrast). If the ruler was several feet away, then the numbers, letters, and lines would be small enough to serve that purpose. As it is, the smallest numbers are over 20 pixels wide. Only the scuff marks would be small enough to demonstrate aliasing, but their contrast is too low to do it. It seems to me that the only area that could alias is the table itself (the part of it that is in critical focus), since it is the only part of the image with fine lines. And I do indeed see some aliasing there: some of the lines have jaggies. I see what could be some terrible chroma aliasing, but given the age of this sensor, I bet it's just noise.
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BartvanderWolf
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« Reply #163 on: January 12, 2010, 05:45:29 AM »
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Quote from: Phil Indeblanc
Perhaps they are not jumping...Are there any artifacts like we have been discussing?..maybe point a couple things out?

Hi Phil,

The DOF seems to be shallow, and the focus is maybe at a distance where the lens is not at it's best. Using out-of focus areas functions as an effective low-pass filter. The aperture data is missing from the EXIF, which makes it difficult to come to a conclusion, other than that this is not a shooting scenario that will usually show a lot of aliasing.

It also doesn't look like something that's better than could be expected from a camera with an AA-filter + proper sharpening, so for me it is not a useful demonstration of ..., whatever it should demonstrate.

Cheers,
Bart
« Last Edit: January 12, 2010, 05:47:40 AM by BartvanderWolf » Logged
Phil Indeblanc
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« Reply #164 on: January 12, 2010, 10:22:37 AM »
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The #16 on the ruler is what is focused on.  This Should have shown defraction as it is F22. I took also at two other stops.

Maybe I should back out another foot?
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ErikKaffehr
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« Reply #165 on: January 12, 2010, 10:54:45 AM »
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Hi,

f/22 would act as a very crude AA-filter.

Check this figure: http://83.177.178.7/ekr/images/stories/difractionlimit.gif

Best regards
Erik

Quote from: Phil Indeblanc
The #16 on the ruler is what is focused on.  This Should have shown defraction as it is F22. I took also at two other stops.

Maybe I should back out another foot?
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Phil Indeblanc
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« Reply #166 on: January 12, 2010, 01:41:19 PM »
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Quote from: ErikKaffehr
Hi,

f/22 would act as a very crude AA-filter.

Check this figure: http://83.177.178.7/ekr/images/stories/difractionlimit.gif

Best regards
Erik



Do you think there would be a difference for the sharpness in the focus area at F11 or 8?



The relation of this lens and the sensor, are rather very nice, as you don't really see defraction. At least I don't.
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BartvanderWolf
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« Reply #167 on: January 12, 2010, 02:00:40 PM »
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Quote from: Phil Indeblanc
Do you think there would be a difference for the sharpness in the focus area at F11 or 8?

Green wavelengths at anything narrower than f/8, maybe f/9, will probably be visibly affected by diffraction due to the diffraction pattern exceeding the sensel size of the Kodak by a significant margin. How the lens and effective sensel aperture interact, I don't know.

Cheers,
Bart
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Phil Indeblanc
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« Reply #168 on: January 12, 2010, 02:09:34 PM »
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Quote from: BartvanderWolf
Green wavelengths at anything narrower than f/8, maybe f/9, will probably be visibly affected by diffraction due to the diffraction pattern exceeding the sensel size of the Kodak by a significant margin. How the lens and effective sensel aperture interact, I don't know.

Cheers,
Bart


I have photographed the same image in 8 and 11 and 16.

I would like to learn more, but my observations when I tested a Canon vs this Kodak, at a given aperture, the files are MUCH crisper, much sharper, much more 3d like.  I do remember when I ran the test that the Canon 1Ds(11mp) would show deffraction before the Kodak(I could be wrong and I will test it as soon as I get all my Canon bodies back).

If I am able to remove all of the Canon AA filter, I would.  But the fact that only 1 is removalable, makes it little point.  The Sony A900 is another option.  If it is able to be AAfilter free, I would not hesitate to take the Sony over the Canon, simply for this reason.

These to me are tools, and may the most adaptable tool be the one I use for the right job.
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ErikKaffehr
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« Reply #169 on: January 12, 2010, 02:34:36 PM »
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Hi,

The effect is called diffraction. Diffraction is simply laws of physics, nothing lens or sensor can do about it. In general diffraction starts to deteriorate an image around or past f/8, depending on
  • residual errors in lens
  • wavelength of light
There is no way of counter acting diffraction. The only way deterioration by diffraction can be avoided at small apertures is bad technique:
  • A really awful lens
  • Bad focus
  • Camera vibrations
The diffraction will still be there but it may be masked by the other effects. On the positive side, diffraction will reduce/eliminate aliasing and it responds well to simple sharpening methods like unsharp mask.

Here is a good discussion of diffraction: http://www.cambridgeincolour.com/tutorials...photography.htm

That said, the human vision can be quite tolerant of unsharpness. I once had a discussion about the effect of MLU on tripod, so I shot a series of test shots with/without MLU. Both series of images looked sharp to me, but when I actually measured MTF with Imatest half the resolution was gone when not using MLU, so I really converted my 12.5 MP camera into a 3 MP camera. Rechecking the images I could see that there was a loss of sharpness. Often you see what you expect/hope to see.

Best regards
Erik

Quote from: Phil Indeblanc
Do you think there would be a difference for the sharpness in the focus area at F11 or 8?



The relation of this lens and the sensor, are rather very nice, as you don't really see defraction. At least I don't.
« Last Edit: January 12, 2010, 02:35:46 PM by ErikKaffehr » Logged

Phil Indeblanc
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« Reply #170 on: January 12, 2010, 03:03:11 PM »
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Quote from: ErikKaffehr
Hi,

The effect is called diffraction. Diffraction is simply laws of physics, nothing lens or sensor can do about it. In general diffraction starts to deteriorate an image around or past f/8, depending on
  • residual errors in lens
  • wavelength of light
There is no way of counter acting diffraction. The only way deterioration by diffraction can be avoided at small apertures is bad technique:
  • A really awful lens
  • Bad focus
  • Camera vibrations
The diffraction will still be there but it may be masked by the other effects. On the positive side, diffraction will reduce/eliminate aliasing and it responds well to simple sharpening methods like unsharp mask.

Here is a good discussion of diffraction: http://www.cambridgeincolour.com/tutorials...photography.htm

That said, the human vision can be quite tolerant of unsharpness. I once had a discussion about the effect of MLU on tripod, so I shot a series of test shots with/without MLU. Both series of images looked sharp to me, but when I actually measured MTF with Imatest half the resolution was gone when not using MLU, so I really converted my 12.5 MP camera into a 3 MP camera. Rechecking the images I could see that there was a loss of sharpness. Often you see what you expect/hope to see.

Best regards
Erik


Deffraction is the result of (as I unsderstood it) is the reaction of light off the aperture blades. the closer they get to each other and the relation to the size of the hole.  Varing lens will deffract differntly depending on the size/cut/shape of the aperture blades.
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ErikKaffehr
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« Reply #171 on: January 12, 2010, 03:12:51 PM »
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Hi,

You are right, sort of, but the effect you are thinking about is second order when you stop down long enough, like beyond f/8. The cause of diffraction is the size of the hole not the blades themselves. I'd suggest that you effect you are describing is probably for real, but not relevant in this context. I'd suggest that you check the link I had in the previous posting, or any textbook.

Best regards
Erik



Quote from: Phil Indeblanc
Deffraction is the result of (as I unsderstood it) is the reaction of light off the aperture blades. the closer they get to each other and the relation to the size of the hole.  Varing lens will deffract differntly depending on the size/cut/shape of the aperture blades.
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Phil Indeblanc
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« Reply #172 on: January 12, 2010, 03:43:33 PM »
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Quote from: ErikKaffehr
Hi,

You are right, sort of, but the effect you are thinking about is second order when you stop down long enough, like beyond f/8. The cause of diffraction is the size of the hole not the blades themselves. I'd suggest that you effect you are describing is probably for real, but not relevant in this context. I'd suggest that you check the link I had in the previous posting, or any textbook.

Best regards
Erik


I have tested a leica 100 vs canon 180 canon. The Canon lens itself is very sharp, but when stopped, The canon shows deffraction sooner, the Leica performed better f22 vs f22.  This is from memory, I will have to revisit.

Learning these things is one thing.  My intention is to making a tool...  Process of elimination is my approach of learning for choosing the right tool :-)
« Last Edit: January 12, 2010, 07:24:38 PM by Phil Indeblanc » Logged

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joofa
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« Reply #173 on: January 12, 2010, 07:48:48 PM »
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Quote from: BartvanderWolf
In a way, yes because RL is based on a Bayesian approach to Poisson noise (just like Photon shot noise), but with improvements like additional insensitivity to random noise.

Richardson-Lucy converges to maximum likelihood solution. The maximum likelihood solution may not be the "best" solution in this case but it is unbiased. Of course, the whole thing may be seen in light of Bayesian statistics.
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Phil Indeblanc
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« Reply #174 on: January 13, 2010, 01:49:23 AM »
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Quote from: Phil Indeblanc
I have tested a leica 100 vs canon 180 canon. The Canon lens itself is very sharp, but when stopped, The canon shows deffraction sooner, the Leica performed better f22 vs f22.  This is from memory, I will have to revisit.

Learning these things is one thing.  My intention is to making a tool...  Process of elimination is my approach of learning for choosing the right tool :-)


perhaps, the relation of the lens to the sensor pixels Im sure play a larger part
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Phil Indeblanc
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« Reply #175 on: January 15, 2010, 02:10:38 PM »
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After much thinking if I should get the 50D to do the test, I figured there would be yet another crop facor. So the closest one I thought would make sense also keeping the camera was the 5Dii, so I purchased it.  It doesn't have a 50 ISO setting.  but from looking at the files...this is a rather nice camera.

My set did move from the time I posted the image to now, so i will do an apple/apple image comparison. and do the YouSend...but from the last post,  Everyone loved explaining their own understanding , and looked like there were plenty to want to listen or learn, but no one but Erik cared to actually look at the test, or the first image of at least...your thoughts?
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ErikKaffehr
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« Reply #176 on: January 15, 2010, 02:45:43 PM »
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Hi,

To begin with I hope that you like your new camera!

The other issue I would say that you kicked of several good discussions and several knowledgeable persons chimed in. It may even be that we get some new and better tools because new ideas have been discussed.

Best regards
Erik


Quote from: Phil Indeblanc
After much thinking if I should get the 50D to do the test, I figured there would be yet another crop facor. So the closest one I thought would make sense also keeping the camera was the 5Dii, so I purchased it.  It doesn't have a 50 ISO setting.  but from looking at the files...this is a rather nice camera.

My set did move from the time I posted the image to now, so i will do an apple/apple image comparison. and do the YouSend...but from the last post,  Everyone loved explaining their own understanding , and looked like there were plenty to want to listen or learn, but no one but Erik cared to actually look at the test, or the first image of at least...your thoughts?
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« Reply #177 on: February 14, 2010, 01:13:44 PM »
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Daniel why is the frequency of the moire in the non AA image on the rivets for the diagonal beam low and if indeed each rivet is represented by more than one pixel why are some rivets missing, unless of course, these rivets are not bright chrome but colored and/or missing. Is it not a possibility that the AA filter reconstructed missing rivets from surrounding pixels by averaging; are all the rivets exactly uniform?

Quote from: Daniel Browning
Excellent! Most people who see this picture prefer the aliased version, so it's nice to meet another person who dislikes the aliasing in it as much as I do, at least for images where the aliasing is extremely bad.

Now the only question is about circumstances where the aliasing is much more subtle (which is usually the case when comparing filtered-vs-filterless cameras).



I am talking about raw. The reason I gave you the extreme example was to set a baseline. If you had preferred the aliased image in the extreme example (as many do), then I would know that you prefer the aliased image in a more subtle example for sure.

Now let's take a look at the following somewhat flawed comparison between an SD14 (no AA filter) and a 50D (relatively weak AA filter).

Here is the SD14 100% crop:



And here is the 50D 100% crop (after downsampling to the same pixel count):



The full SD14 image

The full 50D image.

The purpose of the comparison was not to show the difference between filtered and unfiltered cameras, so it is somewhat flawed for the purpose of this thread, but I think it can still illustrate some of the types of  aliasing artifacts that are seen with filterless cameras.

This example does not have aliasing that is quite as extreme as my last example, but it is a man-made subject, where more people tend to object to the aliasing artifacts.

For example, there appear to be many missing rivets in the SD14 image, while they are all there in the 50D image.

Do you feel the same way about this aliased image as you did the last (i.e. "horrible")? Or do you see the aliased image as having better sharpness/3D than the anti-aliased one? If the former, then the next task will be to find a comparison where the difference in aliasing is more subtle.
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fredjeang
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« Reply #178 on: February 14, 2010, 02:51:25 PM »
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I recommend then to all of AA's troubled to purchase a SD14! if the AA is disturbing your thoughts. The Sigma is just down-priced to such ridiculous level that ones can buy it just to try.
I've worked with the SD14 during 4 years, both for pro and amateur works.
You know what? Just try it, but in any kind of situations, and you will see rapidly by yourself the...AA.  

Fred
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Phil Indeblanc
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« Reply #179 on: February 14, 2010, 08:23:59 PM »
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Quote from: fredjeang
I recommend then to all of AA's troubled to purchase a SD14! if the AA is disturbing your thoughts. The Sigma is just down-priced to such ridiculous level that ones can buy it just to try.
I've worked with the SD14 during 4 years, both for pro and amateur works.
You know what? Just try it, but in any kind of situations, and you will see rapidly by yourself the...AA.  

Fred


I have tried without the AA... using the SLRC Kodak, and that is why I am a "Pro Optional AA filter advocate" :-)

Just as I did this test when all these posts were going on, I was about to purchase a 50D to do the test, and then decided to get the 5Dmrk2, and It is a very nice camera, and I really like the files. I will have to get some apple to apple files to show sometime soon.
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