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Removing Bayer Mask

Ray Fraser , Mar 13, 2005; 12:35 p.m.

Has anyone ever removed a bayer mask? Please correct me if I am wrong but it should be possible to increase resolution by at least factor of 2. My probably errant reasoning is that there would then be twice as many B&W pixels as green pixels. Are these mask's usually directly attached requiring chemical removal or is it possible to just peel them off? Of course for CMOS imagers with a layer of microlenses, I assume those would be removed along with mask.

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Bob Atkins , Mar 13, 2005; 12:44 p.m.

No

Ben Rosengart , Mar 13, 2005; 02:17 p.m.

I don't understand the reason for Bob's curt (to the point of rudeness) answer.

I am currently trying to get hold of old/discarded/obsolete digicams so I can try to remove the Bayer filters. I figure the first few tries will probably result in destroyed cameras.

One problem with this is that "disposable" point-and-shoots rarely offer RAW output. So really interesting experiments won't be possible. But if removing the filter turns out to be straightforward, maybe I'll try it later on a higher-end camera.

Ray, if you attempt any experiments of your own, please post about them.

Berg Na , Mar 13, 2005; 03:43 p.m.

You may not like Bob's answer but he's right.

First, you won't gain any increase in resolution. The Bayer color matrix does not degrade the luminance channel, it only affects the chrominance channels. Since the final image is formed using the brightness values in every pixel, the full spatial resolution of the sensor is maintained, only the color resolution is interpolated.

The Bayer color matrix is sometimes formed on a glass substrate that's epoxy-glued onto the sensor, or it can be deposited directly on the surface of the sensor. In either case, it is almost impossible to remove it without damaging the chip, whether mechanically (scratching the active surface, or cracking the fragile silicon die), or electrically (the sensors are very susceptible to ESD damage, and the tiny wirebonds that connect the die to the package can be easily broken).

So, in the end you may have to thank Bob for his direct answer...

Godfrey DiGiorgi , Mar 13, 2005; 04:08 p.m.

I agree with Bob.

Godfrey

Michael Spencer , Mar 13, 2005; 04:25 p.m.

Berg Na wrote: "You may not like Bob's answer but he's right".

Well, maybe so, but I learned something from your answer.

Thanks for elaborating,

Mike Spencer

Roger Krueger , Mar 13, 2005; 04:28 p.m.

I don't think it's possible either.

But IF you could, you could then increase resolution somewhat by yanking the antialiasing filter too--monochrome aliasing doesn't look nearly as bad as color aliasing. This probably wouldn't increase max resolving power much (if at all) but would give you better MTF at frequencies approaching the resolution limit

Then there's the issue of speed--I'm not sure exactly how much speed the bayer filter costs, but I've got to believe it's at least a stop. It'll help even more if you're shooting underexposed in very red lighting (for me, shooting a band on stage) the blue channel is generating very little image and a lot of noise, because it's getting very little light. WB is an after-the-fact adjustment, and can't really fix color-balance-induced underexposed channels.

Berg Na , Mar 13, 2005; 06:15 p.m.

I'm really not trying to discourage you here... but even if you manage to strip off the color filter array without killing the chip, the next step will be even more complex: completely rewriting the image reconstruction algorithm in the camera firmware. Without this, the image will be full of odd artifacts since the values of the luminance channel are determined from an expected response from the -- now missing -- Bayer CFA (and there are different versions too).

Bob Atkins , Mar 13, 2005; 07:00 p.m.

"Just say no" - Nancy Regan

"Google is your friend" - Internet Sage

Ben Rosengart , Mar 13, 2005; 09:00 p.m.

Berg Na:

That's why I think that ultimately, the best camera for this type of experiment is one that can produce RAW output. If I got that far, I was planning to try to enlist some help from the fellow who develops dcraw. From what people are saying, it sounds as if I'll be quite lucky to get even close to that stage, especially given my rather limited knowledge of electronics.


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