Digital BW, The Print

Thanks Claude.  Interesting stuff.
 
Tom Baker

claudej1@... wrote:

In a message dated 12/17/2004 8:49:22 AM Pacific Standard Time, 
DigitalBlackandWhiteThePrint@yahoogroups.com writes:

Misinformation is worse than ignorance. I honestly don't want to sound like a 
naysayer here, but I worked as a beta tester/consultant with Foveon and have 
a direct line to their chief engineer. Most of what is written is based an the 
old salesman's credo "BS spoken with conviction sounds better than the 
truth." I hate to see this kind of stuff on any forum and I challenge the writer to 
respond with facts instead of sweet sounding opinions.
I INSERTED MY RESPONSE IN CAPS, SO I'M NOT SHOUTING.

Claude


(There are about 50% more green sensors than those filtered for red
> 
> and blue, once again to provide more luma information.)

THERE ARE TWICE AS MANY GREEN SENSOR ON A NON-FOVEON BAYER ARRAY SENSOR, NOT 
HALF AS MANY. DON'T MAKE THIS KIND OF ERROR ON MY PAYCHECK OR TAX RETURN. THE 
FOVEON HAS ALWAYS HAD THE SAME NUMBER OF SENSORS FOR ALL 3 COLORS.


> 
> Luma is just brightness. It has nothing to do with sharpness. ALL the
> sensors are responding to luma, but each in only one portion of the
> spectrum.


HAS EVERYTHING TO SO WITH MODULATION THEREOF BY THE LENS USING DIFFERENT 
COLOR ILLUMINANCE AND REFLECTANCE, SO IT HAS A GREAT DEAL TO DO WITH IT.

> 
> AntiAliasing is a "cure" to color issues, and has nothing (much) to do
> with luma. The anti-aliasing filter may be physical (which can lend to
> softness issues that can be severe, and easily discernable, or it
> calculated, which produces information depending on how well done the
> algorythms are, and the layout of the sensors.)
> 
> The need for anti-aliasing comes from trying to deal with a
> sensor-group which has two different colors meeting in a sharp line
> across it. 


ANTI ALIASING FILTERS HAVE NO COLOR BIAS, THEY ARE SIMPLY A LOWPASS FILTER 
AND ARE ABSOUTELY CALCULATED IN CONCERT WITH COLOR SMEARING ALGORTITHMS IN THE 
DIGITAL SIGNAL PROCESSORS OF THE SYSTEM. THE SYMPTOMS OF THEIR ABSENCE ON BAYER 
FILTER ARRAYS ARE VISUALLY MANIFESTED IN COLOR, BUT THEY ARE NOT A COLOR 
ISSUE PER SE.

> 
> Thus, if you shoot camera RAW, and select one channel, (any channel)
> you'll get perfectly sharp information, since a pixel in is a pixel out.
> 
> True: the Foveon does not require color anti-aliasing, but that has
> nothing to do with single pixel sharpness.


THE FOVEON ONLY SHOOTS RAW AND HAS EVERYTHING TO DO WITH SINGLE PIXEL 
SHARPNESS. WHERE DID YOU GET THIS BS WHEN TALKING ABOUT BAYER ARRAYS? WHAT IS 
PERFECTLY SHARP? 1/4 OF THE ARRAY PIXEL COUNT? WHAT PICTCH? WHAT FILTER?

> 
> However, all that said, simply take a RAW camera image (say 3024 x
> 2024, as it comes from the S2 pro) and select split channels in Photoshop.
> 
> You'll get three images with different ranges of gray tones, depending
> on the range implicit in the color filter. Each image will be some
> range of "black and white" and each image will be exactly 3024 x 2024,
> and contain just over 6 million pixels... not 1.5 million. 


THIS IS AFTER FUJI DOES THEIR SQUARE ROOT OF TWO, OCTAGONAL TO ORTHOGONAL 
VOODOO MATH, SO IT'S PROCESSED INFORMATION WHICH IS 5/6 INTERPOLATED AND NOT 
NATIVE DATA.

> 
> I have no idea what "real sharpness" is, but, in terms of raw pixels,
> and raw data, from a Camera RAW file, the 6 megapixel image IS twice
> as dense as the 3, and thus provides twice the information to deal
> with, and has, hence twice the resolution.

IT'S NOT THAT SIMPLE.
> 
> Take a camera RAW of 6 megs, and blend the three layers to your liking
> for full tonal range, and you'll have a perfectly sharp 6 meg photo.


YOU ARE STILL TALKING A PROCESSED IMAGE NOT RAW, UNLESS IT''S FOVEON WHICH IS 
RAW. BTW, I HAVE OWNED 4 DIFFERENT FOVEONS CAMERAS FOR 5 YEARS AND PRINTED 
MANY IMAGES FROM THEM, B&W AND COLOR.

> 
> Take the color information out of a 3.5 meg photo, blend the results,
> and you'll still have 3.5 megs of resolution.


COMPARED TO WHAT? NOT ALL PIXELS ARE CREATED EQUAL AND FOVEON PIXELS ARE 
ROUGHLY THE SAME AS TWICE AS MANY BAYER PIXELS IN THE FILE.

> 
> Remember, we're talking B&W here, not color, which is what
> anti-aliasing is used for...


THE SYMPTOMS OF ALIASING SHOW UP IN COLOR THE MOST, BUT AA FILTERS ARE NOT AS 
COLOR DEPENDENT AS YOU SUGGEST. THE COLOR DEPENDENCY OF THE 
LUMINANCE/ILLUMINANCE IS SMALL FRACTION OF THEIR TOTAL EFFECT.

> 
> And it is impossible for there to be such a thing as an "interpolated'
> RAW file: either it is RAW info, or it is interpolated info, but it
> cannot be both, by definition. RAW is what the CCD photo sensors put
> out: period. (I understand the confusion, the tyranny of words, that
> can arise, since the Foveon only puts out a "raw" file, but to keep
> the terminology correct, once that file is interpolated, it is no
> longer "raw" in the sense normally used when speaking of digital
> camera RAW files.


ARE YOU TALKING ABOUT COLOR INTERPOLATION? FOVEON DOES NOT COLOR INTERPOLATE, 
EVER. TYRANNY INDEED.

> 
> Yes, the Foveon is great, particularly for color. Excellent stuff. But
> there is a trade-off on sheer resolution vs the lack of need for
> anti-aliasing. Bottom line, for color, is how you like the result.
> It's the photo, stupid! :-)


THIS IS THE ONLY TRUE STATEMENT YOU HAVE MADE SO FAR. JUST LUCKY I GUESS.

> 
> But for B&W, if using RAW files, then there is no anti-aliasing, and
> no matter how you slice the pie, 3.5 megs is less information than 6.1. 


FOVEON RAW FILES HAVE HISTORICALLY BEEN 12 MEGAPIXELS, 16 MEGAPIXELS (ON 
THEIR MONOCHROME SENSOR, NEVER PRODUCED) OR 10.5 MEGAPIXELS ON THEIR CURRENT X3 
CHIPS. THEY HAVE NEVER BEEN 3.5 IN RAW. THEY ARE 4.5 ON THEIR SMALLEST CHIP, NOT 
YET IN PRODUCTION CAMERAS, BUT FORTHCOMING IN POLAROID CAMERAS, IT WOULD 
SEEM.





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