Decoding the Foveon X3 Direct Image Sensor

Ames, Radishes and Butter

By Sam Chapin–

Perhaps the most common criticism given to digital photography is that it’s “not film.” Something is lost in translation between the two mediums that most people just can’t put their finger on. Well, Foveon has.“Where the difference in color comes from,” said Rudy Guttosch, Vice President of Foveon, in a recent interview with Resource, “is essentially in the way that the color is sensed.”

Behold the beauty in the breakdown

Soon after its inception, Foveon was quick to realize that single-layer color sensors were not cutting it in terms of capturing detailed images. So the company started out building and manufacturing prism cameras that use a glass prism to separate light into its component colors (red, green, and blue), matching each color with a different sensor, in order to mimic the sensor technology found in film cameras.  “There were a lot of manufacturing headaches with the prism camera,” Guttosch said. “Aligning three image sensors was a big problem. So Foveon mined its research database, found this patent, and decided they would build an image sensor based on it. That’s where the X3 got its start.”

Adler, Color Jacket

The X3 is an image sensor that took the three-sensor prism technology and condensed it into a single silicon chip with three layers:  one sensor capturing red, green and blue within the silicon depth. There is an individual layer for each color. Since different wavelengths of light penetrate silicon to different depths, each of the three layers primarily captures its individual color. Building three layers in a silicon semi-conductor process is challenging and many companies did not consider this process to be a profitable or worthwhile venture.

three-layer sensor technology

Most digital cameras are forced to take shortcuts with their image sampling because their sensors are not equipped to digest all the data a single image contains. The X3 relies on technology that allows light to be naturally and completely absorbed, resulting in a more vibrant picture. Foveon pioneered the three-layer sensor technology for digital cameras, but in order to put it into practice, they had to find a worthy host. “Sigma has always made good lenses, and now they’re making some truly outstanding ones. You need a lens that can do that three-layer sensor—that complete sampling— justice.”

Sigma and Foveon had collaborated years earlier on their first digital camera, the SD9. In the following years, several more models followed including Sigma’s DP series, a truly groundbreaking product which incorporated a DSLR image sensor in a compact camera body.

In November, 2008, Sigma purchased Foveon and they went to work on building their next camera—the SD1. This new camera made use of an X3 image sensor with more than 3 times the pixel count of the previous Sigma camera generation. The increase in pixel count helped demonstrate the unique nature of the images the camera would produce. “People have talked about the three-dimensional look you get, which is due to a lot of things, but one thing that contributes to it, in my opinion, is the fact that we’re sampling the entire image properly. In other words, we’ve got full red, full green, full blue information, we’re not interpolating—we’re not guessing.” Although the X3 technology is certainly a breakthrough in the image sensor market, Guttosch conceded that there are certain jobs that it wouldn’t be suited for.

“There are a lot of different reasons to buy a particular digital camera. Some photographers have to have ten frames per second for what they do…Well, that’s not necessarily our strongest area, because we’re taking so much more data to make that detailed image.” The camera is for people who have a good amount of light to work with–people who shoot outdoors—landscape photographers, nature photography–and people who can control their light in the studio.


But above all, said Guttosch, what they are concerned with is realism. “The idea of the Foveon sensor was born in reproducing reality, not reconstructing it. And that’s where our real strength lies. For photographers who are looking for that kind of realism in their images, this is the technology that they should seriously consider.” The X3 sensor documents moments authentically and accurately. It is able, through the three-layer technology that it utilizes, to thoroughly study a moment in time and to give the most honest depiction of it as possible—to capture truth.

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