Dump that AA filter - Hot-Rodding your dSLR

[Iron Flatline]

Found an interesting site...

Not sure who exactly LDP / MaxMax are. I found the link in a thread over at the Leica Forums. They do camera conversions and remove IR filters, or AA filters. Check out their site.

The AA removal/conversion is particularly interesting.

Pasted directly from their site:

[FONT=Arial, Arial, Helvetica][FONT=Arial, Arial, Helvetica]All digital SLR cameras contain a piece of glass called the Anti-Aliasing (AA) or Blur filter to prevent Moiré patterns. If you are not already familiar, Moiré patterns are repeating light and dark bands that can occur when photographing a repeating pattern like a screen door or herringbone shirt with a digital camera. When the pattern spacing approaches the pixel spacing on the sensor, you can get a Moiré pattern which is a digital artifact that occurs when sampling resolution (the CCD or CMOS) approaches the signal frequency (such as the lines of a screen door).
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[FONT=Arial, Arial, Helvetica]To eliminate or reduce Moiré patterns, the camera manufacturers install an AA filter to blur the high frequency information. The AA filters lets the low frequency information through but blocks the high frequency. Thus, although you may own a 10 mega pixel camera, it may only be taking an equivalent of 7 mega pixels of resolution. Any information approaching the resolution of the sensor must be blocked to prevent Moiré, but the cost of this is loss of resolution.[/FONT]
[FONT=Arial, Arial, Helvetica]
[/FONT][FONT=Arial, Arial, Helvetica]Below is an example illustrating the problem. If the bottom grid represents the image sensor pixels and the top represents a repeating pattern with similar spacing, the camera will sometimes see top pattern correctly and sometimes not. To solve this, the manufactures blur the image slightly so that any pixel level detail is lost. For most photographers, they would rather have the sharpest camera possible because they are more often photographing subjects that don't have these possible repeating patterns. Problems that do occur can often be fixed in a program such as Photoshop though sometimes the moiré is a serious problem that can't be fixed. Our experience has been that the AA filter solution to reduce moiré on a stock camera usually sacrifices image quality for all the photographs were moiré is never a problem - which is most of the time.[/FONT]
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Kinda cool, no?

Here's a link directly to the AA removal page, with various samples, including two RAW files with and without AA filter.

 

[Big Mike]

Interesting...

 

[Iron Flatline]

Here's a study done with a converted D200.

[FONT=Arial, Arial, Helvetica]...as mentioned on other pages, the AA filter is also known as the Blur Filter. Camera makers use an AA filter to reduce or eliminate potential moiré problems; the cost of reducing or eliminating moiré is a loss of camera resolution as well as contrast and color depth.[/FONT][FONT=Arial, Arial, Helvetica]
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[FONT=Arial, Arial, Helvetica]At first we thought the HR enhancement only affected resolution, but we have also learned that the camera's contrast and color depth are also improved on an HR model. The reason color and contrast improve is that the blur filter effectively averages out a number of pixels together. So, if you have some white and some black pixels near the sensor limit, a stock camera will see grey while an HR color will see blacks and whites. On the pictures shown below, this will become clear.[/FONT]

 

[Overread]

The only thing that makes me question the validity of thier argument (barring the fact that it is there job and they are wanting you to pay for their services) is the Order Checkout at the bottom

a little cheeky I feel to assume that that argument is all that is needed to prove their point and make you purchase their product

 

[Iron Flatline]

LOL, yeah. The site is definitely "hand-crafted" looking...

 

[Alex_B]

I sometimes have those problems with the filter still on the sensor, in particular in architectural photography, where you can have many regularly textured surfaces, so I would not dare to remove it as it would get worse.

 

[notelliot]

I've been wanting to do this for a while. Originally with my D70s, now my D300. Kodak's DSLR never had/doesn't have one, which I've heard good and bad about. For portraits and general editorial photos, I think it would be beneficial. For landscape and architectural photography, probably not so much.

 

[Iron Flatline]

Leica (with Kodak sensor) doesn't have one either, which is why the people at the Leica Forum are so aware of this.

 

[Bifurcator]

I think it would increase the apparent resolution for printing but cause more problems than it would solve for LCD display.

Cool find though! Thanks Iron!

 

[Garbz]

I've seen this before, but I'm hesitant. I'd rather a slightly softer image than a horrid moire pattern which can happen in situations as innocently as taking a photo of someone wearing one of many kinds of fabrics. That and their examples really look like sharpened JPGs on the left and unsharpened straight from raw on the right. Looks like the colours have shifted slightly too which is no surprise when you play with the IR filter.

Not sure about anyone else here, but if you're into this level of pixel peeping maybe it's time to grab a film camera and start back at the basics

 

[JerryPH]

Here's a study done with a converted D200.

I read that one a long time ago, it is very interesting indeed! Yes there are some advantages, but apparently there were a few down sides to it. I cannot recall completely if it was something to do with screwing up the metering system, moire or focus... anyways, thought it sounded like a good idea, it did "break" something else.

Like any commercial product, they are all built on compromises. The moment they do something to raise the performance, things like reliability, price or other aspects of performance become issues.