Gvie up on SD1? Pentax K-1/ar7ii? Need advice.

DMillier wrote:

D Cox wrote:

mike earussi wrote:

DMillier wrote:

I can understand in principle why this may be the case for Bayer sensors. But in pixel shift mode? What could be the explanation in pixel shift mode - this effectively bypasses the Bayer pattern...

Pixel shift enables each pixel to be unique, but the Bayer color is also limited by the fixed color filters on the chip. Foveon doesn't have this limitation.

The Foveon colour filters (layers of silicon) are fixed too, but their more gentle slopes allow finer discrimination of hues than the narrow-band filters used in Bayer sensors.

Some say that the Foveon filters lead to increased noise.

Do we have sources for this?

Here's one from a paper by AVC/Foveon:

"3.3 Color matrix effects

The overlap in the spectral response of the three channels, while providing robust information on the wavelength of narrow-band sources, leads to relatively large off-diagonal terms in the color transformation matrix needed to produce tristimulus values. As an example, it can be easily seen that the blue channel in the tristimulus function is much narrower than the blue photo-diode response. To narrow this channel, a large component of the green must be subtracted. The green is reduced by the blue and the red to narrow the peak and the red channel is augmented with the green to shift the peak to a slightly lower wavelength. Figure 7 shows a typical matrix10 that incorporates those features.

While large off-diagonal terms have a negative effect on signal-to-noise ratio, this is generally not more significant than the effect of the absorption losses in color filter arrays. For color filter arrays using yellow-magenta-cyan or other overlapping bands to increase light throughput, large off-diagonal color matrix terms are also needed, negating some of the sensitivity improvement. Those arrangements still absorb at least one-third of the light."

http://kronometric.org/phot/sensor/fov/SD9%20sensor%20in%20depth.pdf

While not exactly false, the last paragraph seems to be a bit like marketing-speak.

In that same paper, they claim an SNR of 61dB for the green layer, which is just over 10 EV, FWTW ...