Originally posted by kh1234567890 The problem is subsampling - in the Bayer sensor there are physical gaps between elements of the same colour sensitivity, this is what leads to Moire artefacts. You can oversample - have more of smaller elements and then low pass filter in software or you can use a birefringent physical AA filter to spread the light just enough in the horizontal and vertical directions only so that a point source image always covers one or more of the rectangularly arranged sensing elements. Smaller sensing elements also collect fewer photons per exposure giving more quantisation noise. The Foveon sensor stacks the three colour sensing elements on top of each other (like a colour film would), making the inter-element gaps much smaller.
Yes, my whole point is that the Bayer matrix will sample at a frequency similar to the Foveon
if we use equal data rates as the basis for comparison (as opposed to equal pixel-counts). The Foveon pixel embraces all 3 colours vertically, the Bayer spreads them laterally, so (crudely, the reality is more complex) a 3-colour Bayer "superpixel" would need to have 3 pixels occupying the same space as a Foveon pixel - hence my suggestion that the Bayer sensor has 3x the pixel-count. Obviously, if you use equal pixel-counts as the basis for comparison, the Bayer would need stronger anti-aliasing as it's sampling at a lower frequency. (I do notice that the Sigma SD1 Foveon marketing describes the pixel-count as 48MP, but this refers to 16MP-worth of 3-colour pixels).
Regarding noise, if you print at the same resolution as the sensor, then, yes, you'll get more noise as you increase pixel-count.
However, if you were to compare high and low pixel-count sensors when printing at a constant resolution (i.e. constant print size), you wouldn't see any difference. How can this be? Well (crudely) the printer will be combining ("binning") pixels in software to make bigger "virtual pixels", which have the same reduced quantisation noise as real bigger pixels. There's nothing wrong with smaller pixels - it's just the high data rates which are currently problematic.