AA-filtering CCD and CMOS

[rljones]

MaxMax (http://www.maxmax.com/hot_rod_visible.htm) offers a AA-filter removal service for several cameras. They've posted results from a Canon 5D.

They claim up to a 30% improvement in resolution. (However, any sensor cleaning features of the camera are lost due to the conversion process.)

It was my impression that the greater the sensor resolution, then moire is less of an issue (or, is this a function more of smaller pixel size, rather than simply more of them per unit area). if this is true, then removing the AA-filter from a 5D2 or a D3x might be useful.

[jing q]

MaxMax (http://www.maxmax.com/hot_rod_visible.htm) offers a AA-filter removal service for several cameras. They've posted results from a Canon 5D.

They claim up to a 30% improvement in resolution. (However, any sensor cleaning features of the camera are lost due to the conversion process.)

It was my impression that the greater the sensor resolution, then moire is less of an issue (or, is this a function more of smaller pixel size, rather than simply more of them per unit area). if this is true, then removing the AA-filter from a 5D2 or a D3x might be useful.

I removed the AA filter on my 5d MkII using Maxmax.
just to let you know they only remove one of two AA filters in the camera since one of the filters is connected directly to the sensor.

Anyway you will see a difference in tiny details especially in an architectural shot, I did one rcently where the amount of tiny detail was beyond what I expected, and yes, there was moire (which is really not a big problem here)

People mention sharpening as having a similar effect but what we're looking at here is more distinct definition of edges of objects in an image.
Sharpening helps abit but seems abit more muddy and flat.

[BernardLanguillier]

I removed the AA filter on my 5d MkII using Maxmax.
just to let you know they only remove one of two AA filters in the camera since one of the filters is connected directly to the sensor.

Anyway you will see a difference in tiny details especially in an architectural shot, I did one rcently where the amount of tiny detail was beyond what I expected, and yes, there was moire (which is really not a big problem here)

People mention sharpening as having a similar effect but what we're looking at here is more distinct definition of edges of objects in an image.
Sharpening helps abit but seems abit more muddy and flat.

Would it be possible for you to post before/after crops?

Thank you.

Cheers,
Bernard

[jing q]

Would it be possible for you to post before/after crops?

Thank you.

Cheers,
Bernard

I'll post a shot from the modified camera, together with some moire. unfortunately don't have a comparison shot to show you, but it may give some insight into the effect of having an AA filter removed

Here are some 100% crops.

Sharpening Amount 0, Radius 1.0, Detail 0
[attachment=17065:wide00.JPG]


Sharpening Amount 25, Radius 1.0, Detail 0
[attachment=17066:wide25.JPG]


Sharpening Amount 50, Radius 1.0, Detail 0
[attachment=17067:wide50.JPG]

Sharpening Amount 50, Radius 1.0, Detail 15
[attachment=17068:wide5015.JPG]

[ejmartin]

MaxMax (http://www.maxmax.com/hot_rod_visible.htm) offers a AA-filter removal service for several cameras. They've posted results from a Canon 5D.

They claim up to a 30% improvement in resolution. (However, any sensor cleaning features of the camera are lost due to the conversion process.)

It was my impression that the greater the sensor resolution, then moire is less of an issue (or, is this a function more of smaller pixel size, rather than simply more of them per unit area). if this is true, then removing the AA-filter from a 5D2 or a D3x might be useful.

Translation of marketing-speak: 30% increase in aliasing.

The AA filter strength is tuned to the pixel size, one only needs to blur the image over the size of a Bayer RGGB quartet in order to damp the aliasing.  As the pixels get smaller, the needed blur gets smaller.  In addition, the effects of lens aberrations and diffraction are fixed, and can do the job of blurring if the pixels are small enough.  So as pixels get smaller, the AA filter can be even weaker since the optics is doing part of the blurring already.  My understanding is that most current P&S cameras have no AA filter for this reason -- diffraction already provides sufficient blur.  Current high-res DSLR's are not yet in the territory that allows removal of the AA filter without substantial aliasing effects.

[Ray]

I'll post a shot from the modified camera, together with some moire. unfortunately don't have a comparison shot to show you, but it may give some insight into the effect of having an AA filter removed

No! Comparisons are all that count when pixel-peeping. No comparisons, no conclusions can be drawn.

[jing q]

this is the file where the crop is from. I can't remember the settings for this. But it'll give you an idea of how small the crop is relative to the whole 21mp picture.

things I noticed after modifying my 5D mkII:

edges are more defined (and CA is more visible also)
abit more subtle detail overall

[attachment=17069:wide1_smalla.jpg]

[jing q]

No! Comparisons are all that count when pixel-peeping. No comparisons, no conclusions can be drawn.

Ray...
I don't owe you anything. I'm posting this stuff as a general favour. And i'm sharing my experience. If you don't like it, pay someone to do the testing for you, or pay to get it done yourself.

[rljones]

thanks jing for posting the images.

[BernardLanguillier]

I'll post a shot from the modified camera, together with some moire. unfortunately don't have a comparison shot to show you, but it may give some insight into the effect of having an AA filter removed

Here are some 100% crops.

Thanks a lot for the crops.

I am honestly not too impressed by these crops, I feel that correct sharpening applied to d3x files results in both sharper and more pleasing images. This could be depending on the lens though, 90% or my images are shot with the Zeiss 100mm f2.0 that is really sharp.

Cheers,
Bernard

[ErikKaffehr]

Hi,

It may be my view that all pictures need som more agressive sharpening. In Bruce Fraser's book on sharpening there was an example that a 6MP camera sans AA-filter would be sharpened amount=240 and radius=0.6, while a 6MP camera with AA filter would need around amount=500. For > 11MP cameras he suggested radius=0.4.

You could try to sharpen at 0.4 and say 300%

Best regards
Erik

I'll post a shot from the modified camera, together with some moire. unfortunately don't have a comparison shot to show you, but it may give some insight into the effect of having an AA filter removed

Here are some 100% crops.

Sharpening Amount 0, Radius 1.0, Detail 0
[attachment=17065:wide00.JPG]


Sharpening Amount 25, Radius 1.0, Detail 0
[attachment=17066:wide25.JPG]


Sharpening Amount 50, Radius 1.0, Detail 0
[attachment=17067:wide50.JPG]

Sharpening Amount 50, Radius 1.0, Detail 15
[attachment=17068:wide5015.JPG]

[ErikKaffehr]

Hi,

I don't think they are correctly sharpened.

Best regards
Erik

Thanks a lot for the crops.

I am honestly not too impressed by these crops, I feel that correct sharpening applied to d3x files results in both sharper and more pleasing images. This could be depending on the lens though, 90% or my images are shot with the Zeiss 100mm f2.0 that is really sharp.

Cheers,
Bernard

[bjanes]

It may be my view that all pictures need som more agressive sharpening. In Bruce Fraser's book on sharpening there was an example that a 6MP camera sans AA-filter would be sharpened amount=240 and radius=0.6, while a 6MP camera with AA filter would need around amount=500. For > 11MP cameras he suggested radius=0.4.

You could try to sharpen at 0.4 and say 300%

Best regards
Erik

Yes, in the original sharpening book, Bruce did capture sharpening in two steps. The first step involved global application (with blend if sliders to protect the shadows and highlights) of the unsharp filter. The radius was determined by the megapixel count of the camera and the amount by the strength of the blur filter. The next step was to sharpen for image content (i.e low frequency or high frequency images) using an edge mask. The final step was output sharpening for screen or print output.

A very interesting Zeiss article on MTF showed point spread functions (PSPs) for a 12 MP full frame digital camera (likely the Nikon D3). The white square represents the pixel size. Coma and other aberrations are shown. Image 7 represents an ideal PSF and image 8 shows the effect of a blur filter. The effect of the blur filter appears rather nasty, but one should remember that the effective pixel size of a Bayer array camera approaches twice the pixel size, since demosaicing involves interpolation from a 2x2 pixel array.

[attachment=17107:ZeissPSFs.png]

Sharpening is critically important for cameras with a blur filter. Rather than using the unsharp mask for source sharpening, some photographers use a deconvolution filter such as Focus Magic. Deconvolution is theoretically attractive since it actually removes blur rather than merely improving edge contrast as with the unsharp mask. However, deconvolution requires that one derive a PSP describing how the blur was introduced. In astronomy when one is dealing with point sources, this is relatively simple. However, for normal photography deriving the PSP is more difficult. The Photoshop Smart Sharpen filter is another deconvolution method and it might also be tried. However, one should still sharpen for image content and output. It is not clear if these steps were done with the posted images. BTW, setting the black point improves the images considerably.

[jing q]

Thanks a lot for the crops.

I am honestly not too impressed by these crops, I feel that correct sharpening applied to d3x files results in both sharper and more pleasing images. This could be depending on the lens though, 90% or my images are shot with the Zeiss 100mm f2.0 that is really sharp.

Cheers,
Bernard

heh this wasn't shot with the sharpest lens. it's a 24-70mm.but I was just posting this as an example.
you wouldn't be able to get better photos with your 100mm because this was shot with a wide angle.

it's not a comparison either so it's not a lab test,it's just a personal opinion, from someone who uses dslrs and medium format backs and scanned film of small to large format, who prints up to 68" for exhibitions.
what i'm saying is that this level of detail is not what I would have expected in the past from dslrs if there was an AA filter present

And what I am saying is that there is value for people (a niche perhaps) not to have AA filters on cameras, and that the doom and gloom about moire is overrated.
It's no big deal removing the AA filter, and I like the quality of files coming out from my camera after having the AA filter removed.
quoting you,
'there are many people around who believe that the lack of AA filter has little value if any in actual detail rendering."

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.

[ErikKaffehr]

Hi,

I'm aware of the Zeiss article. Just a couple of points:

1) The SPF in the Zeiss article seems to contain lightbeams in 45 degree angles, I'd expect 90 degrees. That said I have no expertise in this area.
2) Focus Fixer cares about camera used, maybee they have some kind of PSF for AA-filter

Looking at the stuff from the practical side, Focus Magic doesn't work on Intel Macs if not using Rosetta. I have tried Focus Magic, Focus Fixer and Smart Sharpen in PS and could not really say that one is preferable over the other.

Best regards
Erik

Yes, in the original sharpening book, Bruce did capture sharpening in two steps. The first step involved global application (with blend if sliders to protect the shadows and highlights) of the unsharp filter. The radius was determined by the megapixel count of the camera and the amount by the strength of the blur filter. The next step was to sharpen for image content (i.e low frequency or high frequency images) using an edge mask. The final step was output sharpening for screen or print output.

A very interesting Zeiss article on MTF showed point spread functions (PSPs) for a 12 MP full frame digital camera (likely the Nikon D3). The white square represents the pixel size. Coma and other aberrations are shown. Image 7 represents an ideal PSF and image 8 shows the effect of a blur filter. The effect of the blur filter appears rather nasty, but one should remember that the effective pixel size of a Bayer array camera approaches twice the pixel size, since demosaicing involves interpolation from a 2x2 pixel array.

[attachment=17107:ZeissPSFs.png]

Sharpening is critically important for cameras with a blur filter. Rather than using the unsharp mask for source sharpening, some photographers use a deconvolution filter such as Focus Magic. Deconvolution is theoretically attractive since it actually removes blur rather than merely improving edge contrast as with the unsharp mask. However, deconvolution requires that one derive a PSP describing how the blur was introduced. In astronomy when one is dealing with point sources, this is relatively simple. However, for normal photography deriving the PSP is more difficult. The Photoshop Smart Sharpen filter is another deconvolution method and it might also be tried. However, one should still sharpen for image content and output. It is not clear if these steps were done with the posted images. BTW, setting the black point improves the images considerably.

[aaykay]

No. Not the brand new Nikon D3000 for example, or this year's Sony A220, A330 and A380, or the Pentax K2000 (K-m) and K200D. The Sony 10MP CCD is the main one left is use though; five of the above six use it. I suspect that Sony is squeezing the last value out of its "paid for" DSLR CCD production lines.

The "paid for CCD production lines" of Sony Semiconductor Kyushu, also make ultra-high-end CCD sensors for their video/cine-alta line.  The Sony F35 Cine-alta, where the bare-bones camera costs $250,000 - not including the cost of a single accessory or lens - comes with a 36x24mm 35mm sized CCD sensor.   They have several other models in the Cine-Alta range that also use CCDs exclusively.  Thus Sony will not only "squeeze the last value" but will continue to promote that line for a variety of other applications that may or may not be  DSLR related.  

There have also been rumors about an upcoming 35mm Studio camera with a CCD-sensor from the Sony stable, with around 40MP.  Whether true or not, I have no confirmation but being Sony, I would not rule out anything.  It is well known that for low-ISO applications where shooting speed is not an overriding consideration, CCDs are the preferred sensor type since they don't have areas on the sensor taken up by the secondary circuitry, like CMOS sensors and thus have a lot more of their area dedicated to gathering light, which in turn translates into better quality images (at least at low ISOs and well lit studio conditions).

[Daniel Browning]

Great post, aaykay.

The Sony F35 Cine-alta, where the bare-bones camera costs $250,000 - not including the cost of a single accessory or lens - comes with a 36x24mm 35mm sized CCD sensor.

Minor correction: it's actually 23.6x13.3mm (active area). In cinema, the film runs through the camera "hot dog way" (vertically). Still photographers run film through the camera "hamburger way" (horizontally). They both call it "35mm", but one is much bigger than the other.

The F35 sensor (same as the Panavision Genesis) is interesting for a variety of reasons, and not just its astronomical cost. It has 12 megapixels, in an RGB array (not Bayer), with alternating rows having an ND filter. All 6 pixels are then combined in a proprietary process to generate one single output pixel with high dynamic range (thanks to the ND). So it only puts out 2 MP, which is the maximum that could be utilized by the highly expensive Sony tape system anyway. While I would have expected the design to make it possible for very little aliasing (chroma or luma), the unfortunate reality is that the F35 has a much higher degree of aliasing than its contemporaries.

[aaykay]

Great post, aaykay.



Minor correction: it's actually 23.6x13.3mm (active area). In cinema, the film runs through the camera "hot dog way" (vertically). Still photographers run film through the camera "hamburger way" (horizontally). They both call it "35mm", but one is much bigger than the other.

The F35 sensor (same as the Panavision Genesis) is interesting for a variety of reasons, and not just its astronomical cost. It has 12 megapixels, in an RGB array (not Bayer), with alternating rows having an ND filter. All 6 pixels are then combined in a proprietary process to generate one single output pixel with high dynamic range (thanks to the ND). So it only puts out 2 MP, which is the maximum that could be utilized by the highly expensive Sony tape system anyway. While I would have expected the design to make it possible for very little aliasing (chroma or luma), the unfortunate reality is that the F35 has a much higher degree of aliasing than its contemporaries.

Cool stuff.  I did not know some of these finer points and some of the Film vs Still differences.  Thanks for clarifying.  So is such an RGB sensor design adaptable for (future) dSLRs, than employing Bayer designs ?  Is this similar to the Foveon RGB design ?

[Daniel Browning]

So is such an RGB sensor design adaptable for (future) dSLRs, than employing Bayer designs?

It's possible, but not a good idea. It only made sense for Sony because their tape system cannot record over 2 MP. Our flash cards can record almost any resolution because we have much lower frame rates in still photography, so it does not make sense for us to throw away so much resolution.

Is this similar to the Foveon RGB design ?

No, Foveon takes 3 samples at a single location,  whereas the F35 takes 6 samples at 6 separate locations, then combines them into 1.

[thierrylegros396]

A better idea is to use double read CCD at different polarization to obtain 2 files for HDR.

Almost instantaneously so that you can shoot HDR without tripod !!!

Don't remember where I found that, but they are projects of some manufacturers.

Have a Nice Day.

Thierry