Digital BW, The Print

Carl,

Aren't all sensors monochrome? Surely they only 'see' color by putting
colored filters over them.

Bob Frost.

----- Original Message ----- 
From: "Carl Schofield" <scho@...>


There was some discussion recently in the dpr Kodak dslr forum about
the possibility that Kodak might introduce a monochrome dslr.  The cmos
sensor currently used in the 14n/c cameras is apparently an RGB variant
of an existing monochrome sensor from FIllfactory so it should be
relatively easy for Kodak to produce a monochrome version:

> From: Bob Frost [mailto:bob@...]
>
> Aren't all sensors monochrome? Surely they only 'see' color by putting
> colored filters over them.

The filters are physically deposited on the chip, not suspended over the
chip or clamped onto it mechanically. I would say that that would justify
calling them color sensors.

By the way, a while back, someone posted this link to a guy who will remove
the Bayer filter from certain cameras for a price.

	http://www.irdigital.net/index.html

I expect he uses some chemical means to remove the Bayer filter, but the web
site doesn't say.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

actually they only remove the pice of filter that blocks out infra 
red, the sensor remains untouched.

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul D. 
DeRocco" <pderocco@i...> wrote:
> > From: Bob Frost [mailto:bob@f...]
> >
> > Aren't all sensors monochrome? Surely they only 'see' color by 
putting
> > colored filters over them.
> 
> The filters are physically deposited on the chip, not suspended 
over the
> chip or clamped onto it mechanically. I would say that that would 
justify
> calling them color sensors.
> 
> By the way, a while back, someone posted this link to a guy who 
will remove
> the Bayer filter from certain cameras for a price.
> 
> 	http://www.irdigital.net/index.html
> 
> I expect he uses some chemical means to remove the Bayer filter, 
but the web

> site doesn't say.
> 
> --
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@i...

> From: Ray [mailto:rayweb301@...]
>
> actually they only remove the pice of filter that blocks out infra
> red, the sensor remains untouched.

So you're saying that you wind up with a color sensor with an IR pass filter
over it instead of an IR block filter? Hmmm. I'm suspicious of that, because
the home page shows a beautiful, sharp image made at ISO200, 1/60sec f11. My
DiMage 7, which has no IR block filter, requires IR exposures more like
1/6sec wide open. Furthermore, my results look noisy and not very sharp, and
only the green channel is worth a damn, which doesn't yield the nice black
skies shown in his image.

I'd gladly pay the price of a Canon 300D plus $500 if I could get it with no
Bayer filter and no IR filter, just for straight B&W.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> > Aren't all sensors monochrome? Surely they only 'see' color by putting
> > colored filters over them.
>
> The filters are physically deposited on the chip, not suspended over the
> chip or clamped onto it mechanically.

I'm not sure about what sensors you are specifically talking about, but the
sensor arrays I've designed and designed with, are purely monochromatic
sensors, and the Bayer pattern filter of the same "pitch" is simply placed
on top of the sensor array (and affixed by a mechanical means, or adhesive).

It certainly does make sense that the manufacturing process be done as you
say for sensors that have any decent volume, since the primary use today is
color w/ a Bayer pattern filter, so I don't doubt what you say about *some*
sensors, I've just not physically seen one.

Here is a decent overview of the color filter array:

http://www.fillfactory.com/htm/technology/htm/rgbfaq.htm

and they do clearly say:

"The most widespread method to give RGB color sensitivity to image sensors
is the application of a color filter mosaic array (CFA) on top of a
black&white imager."

Now, how the color filter mosaic array is "applied" to the top of the
black&white imager is left to question.

Regards,

Austin

You're correct. The colour filter array remains. I have done this conversion
myself with a Canon D30, specifically to get IR shots. It works well IMHO.
With an 89b filter the channel sensitivities are R>G=B. Here's a recent
example:

http://www.asla81.dsl.pipex.com/IR_pictures/IR_example_1.jpg

Out of the camera the images have a magenta cast. ON the D30 sensor the CFA
appears to be deposited directly onto the sensor surface. A future project
will be to try and remove the CFA, reinstall an IR blocking filter and shoot
in B/W. Sensor resolution should then improve significantly because colour
interpolation is no longer needed.

Roger

-----Original Message-----
From: Paul D. DeRocco [mailto:pderocco@...] 
Sent: 30 July 2004 04:25
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: RE: [Digital BW] re: Monochrome Sensors

> From: Ray [mailto:rayweb301@...]
>
> actually they only remove the pice of filter that blocks out infra
> red, the sensor remains untouched.

So you're saying that you wind up with a color sensor with an IR pass filter
over it instead of an IR block filter? Hmmm. I'm suspicious of that, because
the home page shows a beautiful, sharp image made at ISO200, 1/60sec f11. My
DiMage 7, which has no IR block filter, requires IR exposures more like
1/6sec wide open. Furthermore, my results look noisy and not very sharp, and
only the green channel is worth a damn, which doesn't yield the nice black
skies shown in his image.

I'd gladly pay the price of a Canon 300D plus $500 if I could get it with no
Bayer filter and no IR filter, just for straight B&W.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...




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> From: Austin Franklin [mailto:darkroom@...]
>
> I'm not sure about what sensors you are specifically talking
> about, but the
> sensor arrays I've designed and designed with, are purely monochromatic
> sensors, and the Bayer pattern filter of the same "pitch" is simply placed
> on top of the sensor array (and affixed by a mechanical means, or
> adhesive).
>
> It certainly does make sense that the manufacturing process be done as you
> say for sensors that have any decent volume, since the primary
> use today is
> color w/ a Bayer pattern filter, so I don't doubt what you say
> about *some*
> sensors, I've just not physically seen one.
>
> Here is a decent overview of the color filter array:
>
> http://www.fillfactory.com/htm/technology/htm/rgbfaq.htm
>
> and they do clearly say:
>
> "The most widespread method to give RGB color sensitivity to image sensors
> is the application of a color filter mosaic array (CFA) on top of a
> black&white imager."
>
> Now, how the color filter mosaic array is "applied" to the top of the
> black&white imager is left to question.

I'm not denying that the underlying sensor is monochrome, and that the color
sensitivity is achieved with filters. I'm only skeptical that the filters
aren't built as part of the chip. For sensors with big pixels, the filter
may be separate, but the pixel pitch on a pro digicam is about 7 microns,
and on a typical consumer camera, it's much smaller. I don't see how they
could possibly build a separate filter, and then stick it to the IC with
micron-level alignment. The filter would have to be thinner than the pixel
pitch, which would make it a fraction of the thickness of ordinary plastic
wrap.

The link you provided (which is very interesting) mentions the use of
polymers for filters. I would think they'd be deposited right on the chip,
and then photo-etched away, because this would be an extension to the normal
semiconductor processing. If this is true, they might still be removable, if
you could find the right solvent.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

> From: Roger Salmon [mailto:james.salmon@...]
>
> You're correct. The colour filter array remains. I have done this
> conversion
> myself with a Canon D30, specifically to get IR shots. It works well IMHO.
> With an 89b filter the channel sensitivities are R>G=B. Here's a recent
> example:
>
> http://www.asla81.dsl.pipex.com/IR_pictures/IR_example_1.jpg
>
> Out of the camera the images have a magenta cast. ON the D30
> sensor the CFA
> appears to be deposited directly onto the sensor surface. A future project
> will be to try and remove the CFA, reinstall an IR blocking
> filter and shoot
> in B/W. Sensor resolution should then improve significantly because colour
> interpolation is no longer needed.

Exactly. And since you wouldn't be tossing away a third of the light in
filters, you'd get much lower noise images for regular B&W.

What kind of exposures do you need to make pictures like the one in your
link?

Also, do you know anything about how the color filters are made on cameras
like the D30, or how they might be removed?

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

That shot was 1/320@f8 iso 200. In its modified form the camera is about as
sensitive as the original.

The CFA looks like it is deposited onto the sensor surface but I haven't had
a high powered microscope on it yet. I can find no references to how the
arrays are applied to the chips. I suspect that suitable solvents will
remove it.

Roger

-----Original Message-----
From: Paul D. DeRocco [mailto:pderocco@...] 
Sent: 30 July 2004 09:14
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: RE: [Digital BW] re: Monochrome Sensors

> From: Roger Salmon [mailto:james.salmon@...x.com]
>
> You're correct. The colour filter array remains. I have done this
> conversion
> myself with a Canon D30, specifically to get IR shots. It works well IMHO.
> With an 89b filter the channel sensitivities are R>G=B. Here's a recent
> example:
>
> http://www.asla81.dsl.pipex.com/IR_pictures/IR_example_1.jpg
>
> Out of the camera the images have a magenta cast. ON the D30
> sensor the CFA
> appears to be deposited directly onto the sensor surface. A future project
> will be to try and remove the CFA, reinstall an IR blocking
> filter and shoot
> in B/W. Sensor resolution should then improve significantly because colour
> interpolation is no longer needed.

Exactly. And since you wouldn't be tossing away a third of the light in
filters, you'd get much lower noise images for regular B&W.

What kind of exposures do you need to make pictures like the one in your
link?

Also, do you know anything about how the color filters are made on cameras
like the D30, or how they might be removed?

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...




Please visit the Group Homepage to check the Files, and other resources as
they are often being updated.

http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

If you wish to receive no emails or just a daily digest, or you wish to
unsubscribe, please edit your Membership preferences by visiting this same
page.

Please follow these basic guidelines:
- As threads develop, trim off excess portions of earlier messages to keep
them short.
- Good manners are required at all time. No personal attacks or flames.
Hostile, aggressive or argumentative users may be removed from the
membership without notice.
- Keep your posts and threads related to the group topic of digital B&W
printing. Users who persistently make off-topic posts may be removed from
the membership.
- By posting on this forum you agree to abide by the group rules and
guidelines, and to abide by the actions and decisions of the group Owner and
Moderators. See Group Topic, Rules and Guidelines in the Files section:
http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/

BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
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> From: Roger Salmon [mailto:james.salmon@...]
> 
> That shot was 1/320@f8 iso 200. In its modified form the camera 
> is about as
> sensitive as the original.
> 
> The CFA looks like it is deposited onto the sensor surface but I 
> haven't had
> a high powered microscope on it yet. I can find no references to how the
> arrays are applied to the chips. I suspect that suitable solvents will
> remove it.

Maybe a patent search would dredge up the information.

-- 

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Hi Paul,

> And since you wouldn't be tossing away a third of the light in
> filters, you'd get much lower noise images for regular B&W.

Well, not IME.  I still have had to use a neutral density filter.  You're
not really "tossing away a third of the light" anyway with the Bayer pattern
filters.  It's a matter of picking an appropriate filter density for the
sensitivity of the sensor combined with the exposure time to give a minimum
of noise.  If you don't have a filter, most sensors will bloom way too
easily.

Regards,

Austin

Hi Paul,

> I'm only skeptical that the filters
> aren't built as part of the chip. For sensors with big pixels, the filter
> may be separate, but the pixel pitch on a pro digicam is about 7 microns,
> and on a typical consumer camera, it's much smaller. I don't see how they
> could possibly build a separate filter, and then stick it to the IC with
> micron-level alignment. The filter would have to be thinner than the pixel
> pitch, which would make it a fraction of the thickness of ordinary plastic
> wrap.

Keep in mind, the "pro digicam" market uses interline sensors, not what are
called "full frame" sensors (like used in high end dSLRs and digital backs
for medium/large format.  So, I agree that for that market (the market that
use high volume interline sensors) as I said, they probably do deposit the
filter material on the array as you suggest.

You said before, and say again, you are "skeptical that the filters aren't
built as part of the chip".  There is no need to be "skeptical", the filters
are not "built as part of the chip" in all cases, which is all I was
pointing out.

Regards,

Austin

Bob and Paul,

> > Aren't all sensors monochrome? Surely they only 'see' color by putting
> > colored filters over them.
>
> The filters are physically deposited on the chip, not suspended over the
> chip or clamped onto it mechanically. I would say that that would justify
> calling them color sensors.

I would say the sensors we are discussing (standard CCD/CMOS sensor arrays,
not Foveon) are monochrome, whether the sensor has a color filter over it or
not...as monochrome means "one color", so even with an R, G or B filter over
it, the sensor elements them selves are monochrome sensors.  As opposed to
the entire sensor array, which may or may not be monochrome.

Regards,

Austin

Austin, Paul, et al.,

Thanks for your observations on the 'monochrome sensor' thread. As a result,
I've become even more intrigued by the thought of how the Bayer color
filters are deposited/positioned and co-ordinated with the IR filters, the
moire low-pass filters and the microlenses that focus the light more
vertically into the sensors.

Bob Frost.

----- Original Message ----- 
From: "Austin Franklin" <darkroom@...>

I would say the sensors we are discussing (standard CCD/CMOS sensor arrays,
not Foveon) are monochrome, whether the sensor has a color filter over it or
not...as monochrome means "one color", so even with an R, G or B filter over
it, the sensor elements them selves are monochrome sensors.  As opposed to
the entire sensor array, which may or may not be monochrome.

Hi Bob,

> Austin, Paul, et al.,
>
> Thanks for your observations on the 'monochrome sensor' thread.
> As a result,
> I've become even more intrigued by the thought of how the Bayer color
> filters are deposited/positioned and co-ordinated with the IR filters, the
> moire low-pass filters and the microlenses that focus the light more
> vertically into the sensors.

I would be very interested in what you find out.  I will email my contacts
at some of the sensor fabs and ask them for more information if you like.

Clearly, microlenses are separate from the sensor array, and the low-pass &
IR filters are separate as well, as these two really have no special
alignment that I am aware of.  In fact, they are typically easily removable
on the MF and LF digibacks I have used.

Regards,

Austin