What the imager has

Started Feb 11, 2014 | Discussions thread
Earthrise Contributing Member • Posts: 670
Re: Color Resolution Zen

FDecker wrote:

yvind Strm wrote:

Kendall Helmstetter Gelner wrote:

Roland Karlsson wrote:

mike earussi wrote:
Which will vary throughout the image, dependent entirely on the value of the four top layer pixels. So some parts of the image could be as low as 5mp whereas other part could be as high as 19mp, color resolution of course.

Yes, and this is an unwanted characteristic. One of the more irritating properties of bayer sensors is its varying resolution.

Now, the Quattro will not vary in resolution, but in color resolution. Not the same thing.

Yes, the irritating part about bayer is varying luminance resolution, because it suddenly drops the plots as far as detail before natural factors like DOF would cause decay.

The other annoying part is the color artifacts, which bring utterly unexpected colors into view where none should be simply based on a pattern.

Agree, I remember the fence pictures you have shown.

The Quattro should be immune to simply "made up" colors, the worst I can possibly see happening is some kind of color bleeding. But because of the top layers also getting some values the lower layers get, you can eliminate a lot of color bleeding kinds of effects simply by having a clear picture of where the boundaries are.

You have an intersting thought about using info from the top layer - it does make sense. I wonder, with the current sensor, it also sees everything on the top level. Is it correct to see that it needs to subtract what it sees on the lower levels to calclulate what the colors of the top level are? Or am I wrong? If that is correct, it is a bit difficult to imagine how this subraction process would be accurate with different (and lower) resulution on the lower layers.

Unfortunately, Kendall's and some others point of view is flawed in this respect. Yes, it is right that the top layer converts some of the "green" and a bit of the "red" photons. But they are indistinguishable to the sensor. You just get one luminance for the top layer (with no color information at all). The trick with Foveon is that you can reconstruct the correct colour because the conversion ratio between B,G and R is well known for each layer (depends on the absobtion depth of the different wavelengths). So, by taking the luminance of the other two layers into account, the primary colour of each individual layer can be re-constructed from the mixture.

Now, the quattro averages out the luminance values of the middle and bottom layers which belong to the four top layers. So, it is no longer possible to accurately re-construct the colours which contributed to the luminance value of a single top layer pixel. Simply because the exact value of the "local" middle and bottom layer of the "original" Foveon is replaced by the average of the "global" (i.e., 2x2) middle and bottom layer.

That a part of the converted photons in the top layer result from G and R photons will not help.

So BGR resolution is 4.9+4.9+4.9, similar to the original sensors, with a 19 luminance overlay?  No interpolation, no demosaicing, just perceived resolution?

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