AA filters

[Lee Jay]

Hasselblad, Leica, Pentax, Nikon, Sony, Olympus, Fuji, Phase One, all wrong. Some guy on the internet correct?

Yes, about natural or realistic detail.

The vast majority of photographers, professional or otherwise, disagree with you.

The vast majority of photographers have little or no technical knowledge, and think having an AA filter is somehow bad - as though companies have been installing a very expensive optical element in their cameras that makes image quality worse, and doing it for their health or something.

 

[Alphoid]

Ontario Gone wrote:
Well I regularly use 1 pixel radius or smaller when sharpening,
sometimes as small as .2 if im processing inside PS with good IQ.

Exactly, it's the threshold of when the sharpening affect stops working. This is the exact opposite of a LPF, which has a threshold of when it stops "softening" based on wavelength.

Incorrect. In most cases, it's something like the -3db point of the filter. Most blur/sharpen filters have a global effect beyond there. AA filters, boxcar filters, and similar are in the minority.

Just for fun I will repeat. I don't use Gaussian deblur, I use Lens smart sharpen with a 0.2 pixel radius, which does not affect the entire image either. Yet, even when viewed at full size, I can clearly see a change in the sharpest areas of the shot. If it's the eyes of a portrait, at full screen, I can see a difference when I toggle it back and forth.

For the purposes of this discussion, that doesn't change the overall picture. An AA blur is localized. What you're doing is not. It's not exactly Gaussian, but it has the same properties.

 

[Ontario Gone]

Yes, I was speaking for those who prefer to buy cameras without AA filters. You are obviously not in that camp. I mean ask around, it's not like im making it up. None of US want moire, or false color, but we are willing to risk that rather rare occurrence in order to get sharper images.

It's not rare. It's nearly every shot.

Here are a few of the sharper shots I took with my K5-IIs that I still have raws of. Feel free to pick them apart pixel by pixel. If there are all of these artifacts, plz Photoshop them with pointers and illustrations.

I owned a K5IIs, shot over 20k with it, I can say from experience that moire and false color were not that common. And this is coming from a pixel peeper.

You just aren't sensitive to this particular type of artifact. Some aren't. CA doesn't particularly bother me. But aliasing artifacts do.

I always thought I was overly sensitive to just about all flaws, to the point I spend as much time on the technical as I do the art. I don't mind, it can be just as fun, but I never took myself for one of the other guys. Again, if I am missing something in these shots plz show me where. FYI I specifically offered shots with lots of hair, as hair has an uncanny knack for showing aliasing (just like telephone wires).

















--
"Run to the light, Carol Anne. Run as fast as you can!"

 

[JanePete]

Moire affecting most scenes is rare, and typically affects small areas.

Whether it's rare or not depends on what type of photography someone does. Some people might never see it and others will frequently see it, depending on many factors.

Rare for most people and most scenes.

You can't make any generalizations, especially without referring to a particular camera. Whether it's rare or not depends on many factors.

I can, and I have. One only has to look at the photos of cameras without blur filters.

That's an invalid comparison.

How so? Do you not view photos with your eyes?

You're also assuming there is a single AA filter for all cameras, and calling it a blur filter indicates you don't understand what it's actually for and why it's needed.

I have assumed no such thing. Try and read more carefully.

The generalization I made is that AA filters reduce overall resolution. That is a commonly accepted fact within the industry and amongst users, professional or otherwise. Anyone with a decent set of eyes can see that. People that are able to spot moire in typically tiny areas of an image should also be able too, assuming they are being objective and honest.

AA filters bandlimit high frequencies that are beyond the limits of the sensor which can't be accurately resolved anyway (and this isn't only about cameras either). Not doing that will result in alias artifacts, or false details not originally in the subject. Moire patterns is just one example.

Read a book on signal theory sometime.

Look up the difference between theory and practice sometime. In every digital photographic case where the AA filters are ditched resolution of the entire image is noticeably increased.

No it isn't. What's increased are alias artifacts, or false detail that wasn't actually there.

What you're claiming is mathematically impossible and no amount of your arguing is going to change math & physics.

Right, so the manufacturers like Leica are simply fooling photographers and what photograPhers are seeing is a figment of their imagination.

Leica does not have the ability to change math and physics.

The fact is that by omitting an anti-alias filter, there will be more aliasing, which is why it's called an anti- alias filter. It's basic signal theory.

A theory that is obviously not working out in practice.

Why? Clearly the entire image of every image is benefitting. For someone that is fishing for the usually tiny effects of moire I find it ironic then that you miss the effect of a blurred image on the entire image for every image.

The benefit comes at a price of alias artifacts. That's why.

What artifacts would those be? You mean actually being able to clearly see the pixels that make up the image? That's a good thing.

Nope. You're twisting things again. If you actually read what I wrote, you'd see that I said what kind of artifacts, and seeing individual pixels is a bad thing, which is why high DPI displays where pixels are too small to be seen are becoming common.

Well, there is obviously a flip side to that that you have deemed as a negative and yet affects the entire image.

We don't see individual pixels in most print sizes and yet they affect image quality.

As a whole they do. Not individually, and you're moving the goalposts. The issue is alias artifacts, which an AA filter reduces and/or eliminates.

That goalposts expression is a favorite of yours, isn't it?

Fact is, AA filters as they are being implemented also take away noticeable amounts of resolution.

I have also never seen in practice a camera with an AA filter eliminating moire. Never.

Nyquist of a 36 mp sensor is high enough so that an AA filter is not as important as with a lower resolution sensor, however, there can still be situations where aliasing can be an issue. There's no getting around that. There is no perfect AA filter and tradeoffs must be made.

I never mentioned anything about a "perfect AA filter."

Comments like that is further proof you don't understand anything about signal theory or aliasing.

I understand what my eyes can see. Perhaps you should tell Leica, and other camera manufacturer, they don't understand either.

You don't understand what your eyes see or you wouldn't be making absurd comments as you have in this thread and others.

Then most photographers must also be making absorb comments, huh?

Other threads? How about sticking to this one?

As they are implemented, they serve no reasonable purpose. In practice with digital cameras they clearly reduce resolution. there's no getting that.

AA filters do not reduce resolution. They bandlimit what can't be resolved, which is a requirement for a properly implemented sampling system. Otherwise you get aliasing artifacts.

Since no perfect AA filter exists, there are tradeoffs to be made. It's just the way it is. We live in an imperfect world.

First you say "AA filters do not reduce resolution" and then you say "no perfect AA filter exists, there are tradeoffs to be made?"

If you understood signal theory, you'd not be asking that.

No, you just got caught contradicting yourself.

 

[Ontario Gone]

More pixels most certainly do have more noise. It's basic physics and there's no getting around that.

What people end up comparing is not just pixel size but different sensor technologies. Smaller pixels in a lower noise sensor may have less noise than bigger pixels in a higher noise sensor because of a different generation of sensor. There is also the rest of the electronics which adds its own noise too (although not typically significant).

The only way you could be right in this is if all of the sensors I mentioned has newer generations that made backwards progress, and those were not the only examples. Why would they do that? Why would a far newer sensor have made steps backwards, especially when it had going for it what you claim is a noise advantage?

This is baffling to me. A sensor that has everything going for it, newer design, less pixels, yet it still manages to lose a fight with yesteryears model. Are Sony and company playing tricks on us? More likely is the idea that pixel counts (or more specifically, read noise) is a real thing but makes such a minute difference that it's not noticeable, even in tests.

But, the myth is greater than the man in this case. Since some people have heard enough about read noise to know of it, but not enough to understand how little it matters, it is the true tempest in a teapot. Add to this people looking at denser sensors at pixel level and all of a sudden we have mass delusion.

 

[Ontario Gone]

Just for fun I will repeat. I don't use Gaussian deblur, I use Lens smart sharpen with a 0.2 pixel radius, which does not affect the entire image either. Yet, even when viewed at full size, I can clearly see a change in the sharpest areas of the shot. If it's the eyes of a portrait, at full screen, I can see a difference when I toggle it back and forth.

For the purposes of this discussion, that doesn't change the overall picture. An AA blur is localized. What you're doing is not. It's not exactly Gaussian, but it has the same properties.

Then plz share exactly what kind of sharpening it is, since it's not Gaussian but has the same properties.

 

[JanePete]

I think this argument can go round and round, bc it's not really about AA filters and signal theory.

Of course it's about signal theory. That defines how digital cameras work.

It's about standards (as much of what is on DPR is about). Nobody is saying AA filters are not needed,

Some people do.

we are saying that the current resolution ceiling imposed by artificial LPF is too low, we would rather deal with occasional moire than deal with less resolution all the time.

It's not the AA filter that's limiting it. It's the sensor. All the AA filter does is band-limit what is beyond the ability of the sensor to properly resolve and would otherwise cause alias artifacts.

And yet in every example I've seen where AA filters are removed real resolution increases.

The problem is that after sampling, you can't remove aliasing because it's indistinguishable from real data.

Things like moire typically only affect very small areas of images, whereas the resolution degradation caused by the AA filter, as they have been implemented, affects the entire image.

You are the type that likes blurrier images so long as moire in tiny areas of the image is reduced. Most photographers are the opposite of that.

The solution is a higher resolution sensor, or oversampling. The tradeoff is that smaller pixels have more noise and there is a lot more data to move and write to a memory card. Those problems are solvable, and eventually will be.

From a practical viewpoint there are no problems since people are obviously enjoying their sharp, high resolution photos. My non-AA filter Sigmas excel at that.

 

[JanePete]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

You can't sharpen what is not there in the first place. Software sharpening only enhances edge detail. It doesn't create detail.

No AA filter = no sale for me.

--
Lee Jay

 

[Lee Jay]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

--
Lee Jay

 

[Lee Jay]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

You can't sharpen what is not there in the first place. Software sharpening only enhances edge detail. It doesn't create detail.

AA filters remove almost no detail. That's why they still allow a little moire - the corner frequency isn't set low enough to prevent it, and so it doesn't remove anything.

 

[JanePete]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

No AA filter = no sale for me.

Yes, I was speaking for those who prefer to buy cameras without AA filters. You are obviously not in that camp. I mean ask around, it's not like im making it up. None of US want moire, or false color, but we are willing to risk that rather rare occurrence in order to get sharper images.

It's not rare. It's nearly every shot.

I owned a K5IIs, shot over 20k with it, I can say from experience that moire and false color were not that common. And this is coming from a pixel peeper.

You just aren't sensitive to this particular type of artifact. Some aren't. CA doesn't particularly bother me. But aliasing artifacts do.

 

[JanePete]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

--
Lee Jay

Looks like pixels to me doing their job unemcumbered.

 

[Lee Jay]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

Looks like pixels to me doing their job unemcumbered.

I haven't seen hair with stairs on it before - at least in real life.

--
Lee Jay

 

[JanePete]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

Looks like pixels to me doing their job unemcumbered.

I haven't seen hair with stairs on it before - at least in real life.

The pixels are squares so if you look close enough you will see "stairs" on diagonal areas.

--
Lee Jay

 

[Lee Jay]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

Looks like pixels to me doing their job unemcumbered.

I haven't seen hair with stairs on it before - at least in real life.

The pixels are squares so if you look close enough you will see "stairs" on diagonal areas.

Only if you don't use an AA filter. The AA filter's job is to remove those stairs.

Those stairs are false detail, and they are why the fonts you are currently looking at on your screen are anti-aliased.

Here's a sample from the link I provide in the other post.

--
Lee Jay

 

[JanePete]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

You can't sharpen what is not there in the first place. Software sharpening only enhances edge detail. It doesn't create detail.

AA filters remove almost no detail. That's why they still allow a little moire - the corner frequency isn't set low enough to prevent it, and so it doesn't remove anything.

Proven wrong time and time again. Remember, the pro-AA crowd, you, are talking bout theory; I am talking about practice. In every instance i have seen where AA filters have been removed and then that camera is compared to another camera of the same model that still has the AA filter, the one without the AA filter is showing more resolution.

I was also addressing your claim of sharpening in software, which you then ignored.

--
Lee Jay

 

[JanePete]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

Looks like pixels to me doing their job unemcumbered.

I haven't seen hair with stairs on it before - at least in real life.

The pixels are squares so if you look close enough you will see "stairs" on diagonal areas.

Only if you don't use an AA filter. The AA filter's job is to remove those stairs.

Those stairs are false detail, and they are why the fonts you are currently looking at on your screen are anti-aliased.

No, digital images are made up of pixels. Look close enough and you will always see stairs on the edges of diagnol elements. No getting around that.

Here's a sample from the link I provide in the other post.

--
Lee Jay

 

[Lee Jay]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

You can't sharpen what is not there in the first place. Software sharpening only enhances edge detail. It doesn't create detail.

AA filters remove almost no detail. That's why they still allow a little moire - the corner frequency isn't set low enough to prevent it, and so it doesn't remove anything.

Proven wrong time and time again. Remember, the pro-AA crowd, you, are talking bout theory; I am talking about practice. In every instance i have seen where AA filters have been removed and then that camera is compared to another camera of the same model that still has the AA filter, the one without the AA filter is showing more resolution.

No, more contrast at the pixel level, not more resolution.

I was also addressing your claim of sharpening in software, which you then ignored.

That's because sharpening in software works to restore that pixel-level contrast, without adding false detail.

 

[Lee Jay]

I'll just do one little part of one of the images. The whole thing looks "crunchy" in the in-focus portions like this one.

Looks like pixels to me doing their job unemcumbered.

I haven't seen hair with stairs on it before - at least in real life.

The pixels are squares so if you look close enough you will see "stairs" on diagonal areas.

Only if you don't use an AA filter. The AA filter's job is to remove those stairs.

Those stairs are false detail, and they are why the fonts you are currently looking at on your screen are anti-aliased.

No, digital images are made up of pixels. Look close enough and you will always see stairs on the edges of diagnol elements. No getting around that.

Here's a sample from the link I provide in the other post.

And I just showed you an example of removing those stair steps. It's above. You didn't see it?

You're always limited by the pixels, but smoothing out those edges is the job of an AA filter - and it works as shown above. The left one is ugly and "crunchy". The right one is smooth and has MORE apparent detail, not less.

The caption starts with, "Figure 1 shows how anti-aliasing increases the apparent resolution of a device..."

--
Lee Jay

 

[JanePete]

Trust me, everybody in this thread would prefer to NOT have moire and false color, they just dislike fuzzy images even more (not to mention moire is relatively rare in the average photo).

Speak for yourself. Cameras that lack AA filters produce artifacts and nastiness that I dislike far, far, far more than slightly (barely) softer shots, which I can sharpen up satisfactorily anyway.

You can't sharpen what is not there in the first place. Software sharpening only enhances edge detail. It doesn't create detail.

AA filters remove almost no detail. That's why they still allow a little moire - the corner frequency isn't set low enough to prevent it, and so it doesn't remove anything.

Proven wrong time and time again. Remember, the pro-AA crowd, you, are talking bout theory; I am talking about practice. In every instance i have seen where AA filters have been removed and then that camera is compared to another camera of the same model that still has the AA filter, the one without the AA filter is showing more resolution.

No, more contrast at the pixel level, not more resolution.

Odd, I could have sworn the pro-AA crowd has said before that AA filters do not affect contrast. Which is it?

When I can see or read actual detail that where I couldn't before, then that's more resolution. Simply adding more contrast would not have achieved that on a camera with a AA filter.

I was also addressing your claim of sharpening in software, which you then ignored.

That's because sharpening in software works to restore that pixel-level contrast, without adding false detail.

Software sharpening adds no detail, period. That's my point. You suggested otherwise.

--
Lee Jay