From: Nervous Nick on
On Apr 13, 3:30 pm, "Charles Schuler" <charleschu...(a)comcast.net>
wrote:
> "David Dyer-Bennet" <d...(a)dd-b.net> wrote in message
>
> news:461fb9b6$0$952$8046368a(a)newsreader.iphouse.net...
>
> > Is any company offering removal of the Bayer filter from a Nikon-mount
> > DSLR? Particularly the D40? (I suspect it may not be feasible due to the
> > stacking order and how the microlenses, AA, IR cut, and Bayer are
> > combined, and other issues, and I haven't been able to Google up much, but
> > I thought asking might still turn something up.) I'm interested in a
> > high-sensitivity B&W camera for low-light situations.
>
> Interesting idea. Would one necessarily lose the micro-lenses as well and
> would that mitigate against removal? I don't really know, by the way. Here
> is an interesting link that might be helpful:http://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html

That is a *really* informative link, Charles. Thanks, man. It is
pretty technical, but goddam thorough.

--
YOP...

From: David Dyer-Bennet on
cgiorgio wrote:
> "David Dyer-Bennet" <dd-b(a)dd-b.net> schrieb im Newsbeitrag
> news:461fb9b6$0$952$8046368a(a)newsreader.iphouse.net...
>> Is any company offering removal of the Bayer filter from a Nikon-mount
>> DSLR? Particularly the D40? (I suspect it may not be feasible due to the
>> stacking order and how the microlenses, AA, IR cut, and Bayer are
>> combined, and other issues, and I haven't been able to Google up much, but
>> I thought asking might still turn something up.) I'm interested in a
>> high-sensitivity B&W camera for low-light situations.
>
> Certainly nobody will do that, Also you could easily buy a couple of D1 MK 3
> 's plus assorted lenses for the cost of doing that.

I can't tell if you know more than me on this topic, or less. I don't
believe that the Bayer filter is fabricated directly on the sensor as
part of the manufacturing process in most cases, but I don't have a good
specific source to point to, either.

I do know that a number of places offer cameras with the IR-block
filters removed, and there are instructions floating around for how to
do that yourself in various models. The cost for the commercial
versions is modest.

> It would be a more
> realistic approach to cool the sensor with liquid nitrogen (and float the
> camera with dry nitrogen to keep water out) to achieve a higher signal /
> noise ratio. A full frame sensor camera or a larger than full frame camera
> (like Mamyia) would be the easiest solution for achieving improved signal to
> noise ratio.

I very much doubt that LN cooling is feasible today for a camera I could
use to take photos at dimly-lit music parties.

A larger-sensor camera would have lower noise, but it would use much
slower lenses; this is why photojournalism and especially street
photography migrated to 35mm in the first place.

> In production multiple sensors are processed on a wafer (4", 6" or 200 mm)
> and only separated after they have run through all the processing steps
> (except for bonding).
>
> Even if a pin compatible black and white version of the original sensor
> would exist, it would need custom developed image processing (ASIC's and
> firmware) because processing black and white pixels can not use the same
> weighting used as for processing the signals from a Bayer matrix sensor.
> Recording in RAW and using a customized external converter program to obtain
> an image from that would be slightly easier - but probably not for any *.nef
> files, as these are not true RAW but store pre processed data. The camera
> display would also be pretty useless, but I did not have that on my film
> cameras and could still take pictures.

Digital IR photos are frequently taken by using a visible-light-blocking
filter. This greatly reduces the sensitivity, but usable IR photos can
be taken with most digital cameras this way. I believe the dyes in the
Bayer filter are mostly transparent in the infrared (or at least all the
colors are about the same density in the infrared). With P&S cameras,
the preview is reasonably accurate, and looks mostly monochrome, as does
the captured image. So I'm not at all sure that a rework of the
firmware (or external processing using a true raw file) would be
necessary to achieve usable B&W results. (I've shot infrared with an
Epson 850Z and a Fuji S2 using the Hoya r72 visible-light-blocking
filter). (A rework of the firmware or external RAW processing with a
special B&W version of the software might give some real increase in
resolution, though.)
From: John Sheehy on
"cgiorgio" <udlike(a)toknow.org> wrote in news:evot27$cd0$01$1(a)news.t-
online.com:

> Even if a pin compatible black and white version of the original sensor
> would exist, it would need custom developed image processing (ASIC's and
> firmware) because processing black and white pixels can not use the same
> weighting used as for processing the signals from a Bayer matrix sensor.

All a firmware or hardware needs to do is use a certain WB setting to
display the grey RAW data as grey RGB on the LCD, or in the JPEGs, and bias
the metering. The only artifacts might be slight color fringing in high-
frequency high-contrast content, when zoomed in sufficiently. If the
camera already has B&W mode (intended for the CFA), that won't even happen.

--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS(a)no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
From: David J. Littleboy on

"David Dyer-Bennet" <dd-b(a)dd-b.net> wrote:
> Is any company offering removal of the Bayer filter from a Nikon-mount
> DSLR? Particularly the D40?

Unlikely. Although I've not looked into the Sony APS-C sensors, their P&S
sensors build both the microlenses and color filters into the chip. Since
even the slightest registration error would be a complete disaster, it's
unlikely that the color filters are any different on the APS-C sensors.

> (I suspect it may not be feasible due to the stacking order and how the
> microlenses, AA, IR cut, and Bayer are combined, and other issues, and I
> haven't been able to Google up much, but I thought asking might still turn
> something up.) I'm interested in a high-sensitivity B&W camera for
> low-light situations.

Since the color filters are largely transparent to IR, the best you get is a
reasonably sensitive IR camera by removing the IR cut filter (and maybe the
low-pass filter).

High on my wish list is a dSLR with interchangeable sensors. It should be
possible. A 5DII with both a 16MP color sensor and an 8MP B&W sensor would
be seriously neat. I'd certainly cough up between US$700 and US$1000 for the
8MP sensor.

David J. Littleboy
Tokyo, Japan


From: David Dyer-Bennet on
David J. Littleboy wrote:
> "David Dyer-Bennet" <dd-b(a)dd-b.net> wrote:
>> Is any company offering removal of the Bayer filter from a Nikon-mount
>> DSLR? Particularly the D40?
>
> Unlikely. Although I've not looked into the Sony APS-C sensors, their P&S
> sensors build both the microlenses and color filters into the chip. Since
> even the slightest registration error would be a complete disaster, it's
> unlikely that the color filters are any different on the APS-C sensors.

And that's the answer I'm getting from people who actually perform
conversions, too. I'm not surprised; but I was hoping my vague ideas
were *wrong*. Oh well.

>> (I suspect it may not be feasible due to the stacking order and how the
>> microlenses, AA, IR cut, and Bayer are combined, and other issues, and I
>> haven't been able to Google up much, but I thought asking might still turn
>> something up.) I'm interested in a high-sensitivity B&W camera for
>> low-light situations.
>
> Since the color filters are largely transparent to IR, the best you get is a
> reasonably sensitive IR camera by removing the IR cut filter (and maybe the
> low-pass filter).

That has its own temptations, but completely different ones. And not so
tempting for me (though I've done IR a little with my last two digicams).

> High on my wish list is a dSLR with interchangeable sensors. It should be
> possible. A 5DII with both a 16MP color sensor and an 8MP B&W sensor would
> be seriously neat. I'd certainly cough up between US$700 and US$1000 for the
> 8MP sensor.

Something like that would be really nice.