Tuesday, September 7, 2010

Foveon Sensors Are Cool

In my discussion of various types of cameras and the sensors they hold, I forgot to mention the Foveon sensor. I've never really gotten a chance to play around with one of these cameras and wish I could do so without buying the damned camera.

A funny thing about digital cameras is that the numbers they give for megapixels are total horse shit. Yes, a camera may have 15 megapixels (million), but none of them actually register red, green, and blue. They only register one of the colors. So if you're in with the monitor lingo, they'd be more accurately be described as subpixels, since it takes a red, green, and blue to make a full pixel. So in a sense, the true megapixels rating of any camera you may buy is whatever they advertise divided by three.

They cobble together an image from this because the pixels are layed out in a grid where each color is bordered by three other pixels of the other two colors. This allows the computer to interpolate a full color for each pixel. Thus, each subpixel becomes a "true" pixel after software analysis.

Foveon has introduced a new sensor that's actually kind of like old 35mm film. You have three layers of sensors that are, in increasing order of wavelength, blue on top, then green, and red. The light that activates one set of sensors is blocked by that layer, but the other wavelengths pass right through. This allows each pixel recorded in the image to require no interpolation. They are true pixels. This means that per-pixel sharpness is AMAZING. There is no interpolation to blur the fine edges of objects, which means that details in complex scenes like forests or fabric aren't lost.

I wish, wishwishwishwishwish, that Foveon's sensor wasn't so damned crappy in low-light and high-ISO. It's noisy as hell. Still, I love doing a lot of long-exposure work in woodsy environments. My Canon APS-C cameras get overwhelmed and I end up with lots of blurring in distant foliage. So, yeah, if you're looking for a camera it might be worth it to check out the Sigma DP2.

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