Foveon colors

Started Dec 3, 2012 | Discussions
guzzibreva1
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Foveon colors
Dec 3, 2012

I have noticed that my Sigma cameras have the ability to differentiate subtle changes in in color better than my Bayer cameras. I notice it mostly in greens. My SD15 also seems to be a bit more color accurate than my Pentax and Sony cameras.

This is difficult to understand since it is known that the color separation of the foveon chip is not as efficient as the Bayer color filter. Most all reviews of Sigma cameras also talk about the great colors, IQ, and saturation at low ISO.

My only guess is that the broad spectrum sensitivity of each layer helps differentiate color at the expense of color noise at lower exposure levels. This could be achieved with the Bayer filters also but then the noise would be similar to the the Foveon. Overall public acceptance of higher speed must be more important than outright IQ.

Sigma SD15
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Laurence Matson
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Blitzmerkur
In reply to guzzibreva1, Dec 3, 2012

It is a shell game over in Bayerland. A well-done one in most cases, but still . . .

guzzibreva1 wrote:

I have noticed that my Sigma cameras have the ability to differentiate subtle changes in in color better than my Bayer cameras. I notice it mostly in greens. My SD15 also seems to be a bit more color accurate than my Pentax and Sony cameras.

This is difficult to understand since it is known that the color separation of the foveon chip is not as efficient as the Bayer color filter. Most all reviews of Sigma cameras also talk about the great colors, IQ, and saturation at low ISO.

My only guess is that the broad spectrum sensitivity of each layer helps differentiate color at the expense of color noise at lower exposure levels. This could be achieved with the Bayer filters also but then the noise would be similar to the the Foveon. Overall public acceptance of higher speed must be more important than outright IQ.

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xpatUSA
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Re: Foveon colors
In reply to guzzibreva1, Dec 4, 2012

guzzibreva1 wrote:

I have noticed that my Sigma cameras have the ability to differentiate subtle changes in in color better than my Bayer cameras. I notice it mostly in greens. My SD15 also seems to be a bit more color accurate than my Pentax and Sony cameras.

This is difficult to understand since it is known that the color separation of the foveon chip is not as efficient as the Bayer color filter. Most all reviews of Sigma cameras also talk about the great colors, IQ, and saturation at low ISO.

My only guess is that the broad spectrum sensitivity of each layer helps differentiate color at the expense of color noise at lower exposure levels. This could be achieved with the Bayer filters also but then the noise would be similar to the the Foveon. Overall public acceptance of higher speed must be more important than outright IQ.

Your experience is opposite to mine but on the SD9 whose color inaccuracy is documented ad nauseam in this forum. I sold mine in despair at those brown reds under artificial lighting which are still evident in the SD1 review on this site. Later, I bought an SD10 which seemed greatly improved in that regard. Meanwhile, my humble Nikon D50 produces very accurate colors in RAW/ACR (camera neutral profile). According to the MacBeth card, anyway.

According to a paper by the Foveon guys, the sensor does not suffer from "color noise" (actually color aliasing).

Public definitely seems to  prefer huge resolution, enormous ISOs, ultra-high frame rates and now HD movies with stereo recording and not forgetting Wi-Fi, Bluetooth, Android with live touchscreens. All that for just a buck or two. Excuse me, while I puke

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SigmaChrome
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Re: Foveon colors
In reply to xpatUSA, Dec 4, 2012

xpatUSA wrote:

Your experience is opposite to mine but on the SD9 whose color inaccuracy is documented ad nauseam in this forum. I sold mine in despair at those brown reds under artificial lighting which are still evident in the SD1 review on this site. Later, I bought an SD10 which seemed greatly improved in that regard. Meanwhile, my humble Nikon D50 produces very accurate colors in RAW/ACR (camera neutral profile). According to the MacBeth card, anyway.

According to a paper by the Foveon guys, the sensor does not suffer from "color noise" (actually color aliasing).

Public definitely seems to prefer huge resolution, enormous ISOs, ultra-high frame rates and now HD movies with stereo recording and not forgetting Wi-Fi, Bluetooth, Android with live touchscreens. All that for just a buck or two. Excuse me, while I puke

No puking on the forum -- if you don't mind!

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guzzibreva1
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Re: Foveon colors
In reply to xpatUSA, Dec 4, 2012

"According to a paper by the Foveon guys, the sensor does not suffer from "color noise" (actually color aliasing)."

This is not correct.

The Foveon colors suffer at high ISO because there is a lot of common mode information in the color channels. This requires more amplification to extract chroma information. When the signals are small, the noise from this amplification noise shows up as hue shifts in the form of blotches.

The up side to this seems to be that the sensor is equally sensitive to all colors whereas the bayer approach favors the primary colors of the array. My Pentax K5 produces images where the greens tend to all look like the were all painted with the same color brush. The highlights lose saturation before clipping also. This is why some people have said the colors look "thicker" in the foveon images.

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Jim Beverlin
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Re: Foveon colors
In reply to guzzibreva1, Dec 6, 2012

Interesting post.  I have 3 Pentax cameras and have just taken images of our highly decorated Christmas tree with a K-05 and a K-01.  Want to try shots with both my 1st D and DP2X too.

With all settings at default I was surprised how much better the K-01 handles reds than the K-5.

Will try the other cameras over the weekend and advise.  I have a number of limtied primes that are used with the K-01 and am really amazed at the quality that I get from this much maligned camera.

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xpatUSA
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Re: Foveon colors
In reply to guzzibreva1, Dec 6, 2012

guzzibreva1 wrote:

"According to a paper by the Foveon guys, the sensor does not suffer from "color noise" (actually color aliasing)."

This is not correct.

I was referring to the content under "Color Aliasing" in this paper:

http://www.foveon.com/files/CIC13_Hubel_Final.pdf

It says this, and more:

"In cameras that employ color filter array (cfa) mosaics aliasing
occurs in the three color planes at different locations. This artifact,
referred to as color aliasing, appears as brightly colored fringes in
locations of image detail at a particular spatial frequency."

Can't see anything incorrect there . . .

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Ted.

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ArvoJ
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Re: Foveon colors
In reply to xpatUSA, Dec 6, 2012

I think that guzzibreva meant that color noise and color aliasing are different things. Foveon concept suffers from relatively high color noise, but not from color aliasing.

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