Advantages of Foveon sensor Locked

Started Jun 23, 2013 | Discussions thread
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Laurence Matson
Laurence Matson Forum Pro • Posts: 11,969
Re: Walk before you run

Just another Canon shooter wrote:

Laurence Matson wrote:

Just another Canon shooter wrote:

Roland Karlsson wrote:

Bobn2 wrote:

What is a 'color gradient'?

To be more specific, what is a 'color'?

A good question.

For an RGB image, a color is an RGB triple in some color space.

In nature, "color" has infinitely many components, it is a "spectral density". Each sensor, Foveon or not, projects it on a 3D space in some way. So does the human eye. Bob's point is that Foveon senors have color vision farther away from the human eye than the Bayer ones. This has nothing to do with spatial separation. It is worse separation in another dimension, which is the spectral one.

If the Foveon sensors has a wider curve in the red part of the spectrum, this does mean that it can see "more colors" but also means that it cannot distinguish between them, like a B&W sensor (with no color filter). If that curve is significantly different than that of the human eye, then it is a poor approximation of the human vision.

Welcome to the Sigma Forum.


Not to be rude, but your second paragraph is a gem of fluff. There are "more colors" and specific wavelengths. I don't really see someone here is saying that a Foveon imager can see "more colors"

This poster did:

Then he can jog with you.

but rather that it sees distinct colors at each spatial location where three pixels scrape together the electrons - simplistically speaking, dead photons (one step beyond Einstein's Nobel Prize winner - at each layer and come up with three sort of distinct numbers, which can be turned into a specific color.

The problem is that it sees "the wrong colors". Three distinct, yes, but not the right three distinct. It has great spatial resolution bit poor, and wrong spectral one. You, and most people here are missing the point - it is about the spectral, not about the spatial resolution. Imagine a uniform colored surface: the Foveon sensor would have hard time recording the color we see, while the Bayer one would get much closer.

I do not think it makes sense to get into a VFA vs. CFA argument. I am not sure how you can define the distinct colors as wrong (or right). It is what is made with them in determining the end result for that spatial location. That is the spectral response for that pixel. I am not sure how you see that as spatial resolution in the first instance; ultimately, it is that as well.

So the key is not that the Foveon imager can see more colors but rather that it theoretically can distinguish colors accurately, with a caveat on all of the last part of the phrase.

Exactly the opposite. The spectral properties of the layers are much worse than those of the CFA filters, relative to the human vision.

This is not true in my experience and from what I know. What is your source for that specifically relating to the theories behind the Foveon imager?

Where the Bayer process relies on a brilliant method of exploring the surrounding pixels to determine what belongs between two good signals, the Foveon process relies on accurately interpreting collected information. Both are forms of interpretation, if you will.

Again, that is spatial resolution, not spectral one.

I would argue that it is secondarily. First you have to have a color at a location.

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laurence at appledore-farm dot com
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