Foveon Sensor


Today’s Question: You discussed the topic of “demosaicing” and touched based on the Bayer sensor. Can you also discuss the Foveon sensor and its potential advantages on capturing color values?

Tim’s Quick Answer: The Foveon sensor captures full color for each pixel, rather than only red, green, or blue for each pixel as with a Bayer pattern sensor. While there are theoretical advantages to the Foveon sensor, there are also limitations that have prevented the Foveon sensor from having a clear advantage over others.

More Detail: As I imagine most photographers are aware, the typical digital camera includes a sensor with a Bayer pattern array, where for each four pixels on the sensor two are capturing only green light, one is capturing red light, and one is capturing blue light.

Because these sensors only capture one out of the three color values per pixel, software must be used to process the resulting image data into a full-color photo. This process is referred to as “demosaicing”.

The Foveon sensor was first used in a camera (the Sigma SD9) in 2002, and I had the opportunity to test that camera at the time. While I was impressed with the technology and the level of detail in the photos from the Foveon sensor compared to other digital cameras at the time, the technology never caught on with the top digital camera manufacturers. In 2008 Sigma acquired Foveon, and several camera models employing the Foveon sensor were released by Sigma over the years.

While there are theoretical advantages to the Foveon sensor based on capturing full-color information, there are drawbacks as well. For example, because light is being absorbed in separate “layers” in the Foveon sensor, the sensor isn’t capturing as much information as you might assume. That translates into a need for additional amplification, which results in noise. The more recent Foveon-based cameras I’ve been able to test exhibited very poor noise performance.

All things considered, I would say that the benefits of the Foveon sensor are outweighed by the disadvantages, and that in general sensors with a Bayer pattern array provide better image quality compared to the Foveon sensor.