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Subject: Re: Superior Technology: Foveon X3

"Gary" wrote:
To capture the color that other image sensors miss, Foveon X3 direct
image sensors use three layers of pixels embedded in silicon. The
layers are positioned to take advantage of the fact that silicon
absorbs different wavelengths of light to different depths. The bottom
layer records red, the middle layer records green, and the top layer
records blue. Each stack of pixels directly records all of the light at
each point in the image.

Nice theory. Except that it doesn't work that way in real life. The color
separation is poor, and decoding color introduces noise. Foveon has to
interpolate its color vertically, whereas Bayer has to interpolate it
horizontally. Six of one, half a dozen of the other.

Also, you have to store three separate charges at each pixel, so the well
depth is that much smaller and the noise that much larger. Strike two.

That approach has inherent drawbacks, no matter how many pixels a
mosaic-based image sensor might contain. Since mosaic-based image
sensors capture only one-third of the color, complex processing is
required to interpolate the color they miss. Interpolation leads to
color artifacts and a loss of image detail. Blur filters must then be
used to reduce color artifacts. The use of blur filters adversely
affects sharpness and resolution of the final image captured.

This is lying FUD. Foveon sensors also require antialiasing filters to avoid
Moire and other aliasing artifacts just as Bayer sensors do. Look up the
mathematics of discrete sampling and the Nyquist theorem.

With its revolutionary process for capturing light, Foveon X3
technology never needs to compromise on quality, so you get sharper
pictures, truer colors, and fewer artifacts.

Snake oil. In real life you get bogus snap-to-grid detail, poor color
reproduction, and more artifacts, since none of the Foveon cameras have the
mathematically required low-pass filter.

And cameras equipped with
Foveon X3 technology do not have to rely on processing power to fill in
missing colors, reducing hardware requirements, simplifying designs and
minimizing lag time between one shot and the next.

Now this is simply a lie. Foveon cameras require three times the data
storage and processing capacity of Bayer cameras (of the same pixel count),
since they have to store three values for each pixel in the RAW format and
have to perform complex processing to decode the color.

David J. Littleboy
Tokyo, Japan


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