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The Foveon X3 Chip
A plain English overview of what 
all the fuss is about

by the Staff at Vivid Light

Until now, you haven't been getting the picture. At least not the complete picture.

That's because revolutionary Foveon X3 technology features the first and only image sensors that capture red, green and blue light at each and every pixel. All other image sensors record just one color per pixel—that's why Foveon X3 technology delivers increased sharpness, better color detail and resistance to unpredictable color artifacts. 
-- From Foveon's Web Site

That's a pretty bold claim. It is true that Foveon's image sensors are different from the CCD and CMOS sensors used in every other digital camera. We'll lay out the differences here so you can understand them and make an informed decision. But while Foveon's technology makes for a good story, one that has been told by every photo magazine, the proof is in the picture. For more information on how the Foveon chip in Sigma's SD-9 stacked up against the CCD in the Nikon D100 click here.

The Underlying concept
CMOS and CCD sensors, which we'll generically call image sensors, use a matrix design to record different colors of light. The color of any one pixel is therefore an interpolated value using the values of the pixels around it. 50% of the information captured is in the green channel, with the remaining 50% split between the red and blue channels. 

Now while that may not sound like a very accurate way to capture color it should be noted that the images from today's digital cameras look pretty darned good. There may be some compromise at the lowest level of capture but this matrix style system is capable of producing some stellar results. 

You may be wondering why green dominates the matrix design. That's because the human eye is most sensitive to green light. Images captured with this mix of red, green and blue appear sharper to we humans because of the way our vision is biased. That said I do find myself sharpening and tweaking the images from almost every digital camera to get exactly the results I'm after.

Foveon's position is that its only common sense that a sensor that doesn't have to interpolate data will produce a more accurate image. But does it? And if it does is it accuracy you can see? 

The reality is that the Foveon is capable of producing high quality images. But we didn't find them to be more accurate or sharper than images produced with a D100 using the same lens. In fact we found the opposite to be true. The Nikon CCD produced more accurate colors and worked well in a wide range of lighting conditions. The Foveon chip did not fair well in low light. 

Engineering 101 teaches us that there is no free lunch. Every design decision involves tradeoffs. Evidently the tradeoff in the Foveon design is decreased light sensitivity compared to competing designs. In fairness this is a first generation design. It will be interesting to see what Foveon's engineers are able to do with this chip as they compete in a VERY hot marketplace. 

You can read a complete technical overview of the X3 chip at Just read with the caveat that we haven't seen the extreme problems shown in the example images with today's current crop of digital SLRs.

Other Factors
The tendency when talking about digital photography is to focus on one component in a vacuum, whether it be resolution or chip design. There are other things besides the image chip that affect the quality of the final image.  

Lens Quality - Lens quality is as much a factor in digital photography as it is in film photography. If you buy one of these expensive digital wonder cameras and slap on a cheap lens you'll get lousy results every time. 

Quality of Engineering - Noise is an issue with any digital camera design. A good example is the difference between Nikon's D1 and D1X/H cameras. The later generation design featured circuit board designs that significantly reduced noise. The result was better images that produced cleaner results in continuous tone and shadow areas. The longer the exposure the more of a factor noise becomes. In digital cameras noise manifests itself as grainy areas and a loss of detail in shadow areas.

Technique - At the risk of bruising a few egos I'll say that with today's cameras the weak link is often the photographer. Technique doesn't just mean using a tripod for long exposures and nailing the composition. It also means taking the time to really understand your gear. Digital cameras are not film cameras. They require an understanding of new concepts and they require you to take the time to experiment and really understand how they work (or don't work) under a variety of lighting conditions. It's akin to the exercise of shooting your favorite film under a variety of conditions and checking the results on a light table to understand how that film works in different circumstances. See The Ultimate Equipment Bargain for the process. It works equally well for digital testing.

Other Factors
Other factors determine the right camera for your needs. They include camera features, handling, and system compatibility. I've heard more than one photographer get so caught up in the latest digital feature that they were talking about trading in their whole camera system for a system from a different manufacturer. Before taking such a drastic (and expensive) step. Be sure you understand what you're buying and whether you can actually see the difference.

If you've been in a system for a while it becomes very expensive to change. Think long and hard before doing so, and make sure you have a compelling reason.

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