Digital BW, The Print

OK, the whole point of doing a monochrome sensor is to REMOVE the  
Anti-Aliasing filter because there is NO color aliasing. There is no  Bayer Filter Array 
on the sensor to start with, so why would you want to fuzzy  up the image?? 
The main strength of a mono sensor is it's twice as sharp as  a color one. IOW, 
it take twice as many Bayer Well Sites to equal the resolution  of a given 
number of mono well site, assuming the optics can resolve both.
 
As a Foveon mentor back in 1999, after being an early Kodak adopter, I  
learned this lesson well by comparing a cropped 3.2 megapixel (1.6k X 2K)  capture 
on the 3-chip prism camera, to a PhaseOne Lightphase AND  a Kodak 560. The 
Phase One had a 6 MPx Philips Sensor and NO AA  filter. The 560 had a 6 MPx 
sensor with AA filter. By far, Kodak's was the worst  performer. Foveon was the 
best, by a nudge, over the Phase One (that back was on  a Hasselblad). We are 
talking about $30,000 outfits here and not today's amazing  camera that cost less 
than $1,000. So those of us who spent that kind of cash  were SERIOUS about 
digital performance and had to make sure we had clients to  pay for it.
 
By the same token, Foveons X3 color sensor in the Sigma SD-10 (best cheap  
B&W capture also) has full color resolution at every well site, and so, at  3.5 
MPx native capture, performs as well or better than most 8 MPx cameras as  far 
as resolution BECAUSE there is not AA or BAYER filter array.
 
Back in 2000, Foveon had a prototype 22x22mm sensor that was monochrome. It  
was all CMOS, 4k x 4k (16 megapixels). Greg Gorman did a shot of a Cowboy in 
the  proto camera that had accepted Canon lenses. They made a 4 foot by 8 foot 
print  (cropping out 1/2 the image area captured by the sensor!!). At 
Photokina,  everyone thought the image was better than 4x5 film. It would have taken a 
36  MPx (6k by 6k) BFA color sensor to perform better than this, assuming the 
optics  could do it.
 
This may bee deemed as my opinion, but I have image files to prove it. I'm  
currently on my 30th digital camera in 10 years.
 
I only wish the Foveon technology would catch on and they could make bigger  
sensors. This way you would have all the shapness benefits of a mono sensor,  
with all of the post-process manipultations of scene renderings during the  
B&W conversion in Photoshop.
 
In the mean time, I suspect that if Ken Boydston of MegaVision decides to  
make a Mono Back that also does IR captures, like everything else he has done,  
someone will copy it.
 
Claude
 
In a message dated 7/10/2005 10:47:24 A.M. Eastern Daylight Time,  
DigitalBlackandWhiteThePrint@yahoogroups.com writes:

I'd  propose an answer to this question. Such a sensor would have no 
Bayer  mosaic, and would have a user-removable IR blocking filter (or no 
blocking  filter at all). In my ideal camera, it would have an 
anti-aliasing filter  (referred to as "blur" filter here earlier), though.


 


[Non-text portions of this message have been removed]

Can you still have monochrome moire?  I believe an AA filter still has value
on a monochrome CCD for that purpose.

John

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of
claudej1@...
Sent: Tuesday, July 12, 2005 9:35 AM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: [Digital BW] Digital Zone System via filters


OK, the whole point of doing a monochrome sensor is to REMOVE the
Anti-Aliasing filter because there is NO color aliasing. There is no  Bayer
Filter Array
on the sensor to start with, so why would you want to fuzzy  up the image??
<snip?


[Non-text portions of this message have been removed]

I'm not sure if I understand everything in this message. But here goes, I 
have Canon 20D that has been modified by Hutech. The IR cut-off filter has 
been removed, and because the anti-aliasing was attached to that filter the 
camera has no AA filter. The filter that was removed was replaced by a 
specially coated clear filter to preserve auto-focusing.
My camera requires an IR filter in front of the lens, which makes difficult 
to shoot because you cannot see through the filter. In the fall Hutech will 
begin producing bodies that have an IR filter in front of the sensor, so 
there will be no filter on the lens and the camera will be dedicated to IR. 
Are not the manufacturers or after market modifiers coming close to a 
dedicated B/W camera?.

Gary

----- Original Message ----- 
From: <claudej1@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Tuesday, July 12, 2005 6:35 AM
Subject: [Digital BW] Digital Zone System via filters



OK, the whole point of doing a monochrome sensor is to REMOVE the
Anti-Aliasing filter because there is NO color aliasing. There is no  Bayer 
Filter Array
on the sensor to start with, so why would you want to fuzzy  up the image??
The main strength of a mono sensor is it's twice as sharp as  a color one. 
IOW,
it take twice as many Bayer Well Sites to equal the resolution  of a given
number of mono well site, assuming the optics can resolve both.

As a Foveon mentor back in 1999, after being an early Kodak adopter, I
learned this lesson well by comparing a cropped 3.2 megapixel (1.6k X 2K) 
capture
on the 3-chip prism camera, to a PhaseOne Lightphase AND  a Kodak 560. The
Phase One had a 6 MPx Philips Sensor and NO AA  filter. The 560 had a 6 MPx
sensor with AA filter. By far, Kodak's was the worst  performer. Foveon was 
the
best, by a nudge, over the Phase One (that back was on  a Hasselblad). We 
are
talking about $30,000 outfits here and not today's amazing  camera that cost 
less
than $1,000. So those of us who spent that kind of cash  were SERIOUS about
digital performance and had to make sure we had clients to  pay for it.

By the same token, Foveons X3 color sensor in the Sigma SD-10 (best cheap
B&W capture also) has full color resolution at every well site, and so, at 
3.5
MPx native capture, performs as well or better than most 8 MPx cameras as 
far
as resolution BECAUSE there is not AA or BAYER filter array.

Back in 2000, Foveon had a prototype 22x22mm sensor that was monochrome. It
was all CMOS, 4k x 4k (16 megapixels). Greg Gorman did a shot of a Cowboy in
the  proto camera that had accepted Canon lenses. They made a 4 foot by 8 
foot
print  (cropping out 1/2 the image area captured by the sensor!!). At
Photokina,  everyone thought the image was better than 4x5 film. It would 
have taken a
36  MPx (6k by 6k) BFA color sensor to perform better than this, assuming 
the
optics  could do it.

This may bee deemed as my opinion, but I have image files to prove it. I'm
currently on my 30th digital camera in 10 years.

I only wish the Foveon technology would catch on and they could make bigger
sensors. This way you would have all the shapness benefits of a mono sensor,
with all of the post-process manipultations of scene renderings during the
B&W conversion in Photoshop.

In the mean time, I suspect that if Ken Boydston of MegaVision decides to
make a Mono Back that also does IR captures, like everything else he has 
done,
someone will copy it.

Claude

In a message dated 7/10/2005 10:47:24 A.M. Eastern Daylight Time,
DigitalBlackandWhiteThePrint@yahoogroups.com writes:

I'd  propose an answer to this question. Such a sensor would have no
Bayer  mosaic, and would have a user-removable IR blocking filter (or no
blocking  filter at all). In my ideal camera, it would have an
anti-aliasing filter  (referred to as "blur" filter here earlier), though.





[Non-text portions of this message have been removed]



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>> OK, the whole point of doing a monochrome sensor is to REMOVE the
>> Anti-Aliasing filter because there is NO color aliasing. There is no  Bayer
>> Filter Array
>> on the sensor to start with, so why would you want to fuzzy  up the image??


> Can you still have monochrome moire?  I believe an AA filter still has value
> on a monochrome CCD for that purpose.


Yeah, that's exactly why I'd want one. Aliasing arises when a signal 
with periodic structure is sampled at a frequency less than the Nyquist 
frequency. There is nothing magical about multichrome or monochrome 
sensors that makes them immune to this phenomenon.

What this means in practical terms is that if the sensor is not Nyquist 
sampling the resolution of the camera lens, aliasing may occur. I have 
taken a number of obviously aliased images with monochromatic science 
cameras, so they are definitely not immune. (The cameras I reference 
don't have antialiasing filters, because they expect the user to be 
smart enough to adopt a suitable sampling frequency.)

It is correct (obviously) that with a monochrome or multichrome camera, 
there is no color aliasing, and this is because the spatial sampling 
frequency does not vary by wavelength. Bayer demosaicing can introduce 
its own aliasing-like effects as well, so (equally obviously) these are 
not present in monochrome or multichrome cameras. Therefore the 
antialiasing filter in a monochrome camera can pass a much higher 
frequency than the one used in a camera with a Bayer mosaic. (The 
low-pass filter used for antialiasing cuts off [not very sharply in 
optical cases] frequencies greater than 1/2 the sampling frequency.) But 
it cannot be eliminated altogether, unless you plan on using an 
extremely high megapixel count (perhaps 60 or more megapixels in 35mm 
format), or rather poor lenses.

--
Jeff Medkeff
Eagle River, Alaska