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Kirata -> RE: Camera Talk (11/17/2011 1:37:57 AM)
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quote:
ORIGINAL: LookieNoNookie
Something about, taking images with this new 'thing" would allow you to expand the photo to something akin to a stadium, with no loss of pixels or some such. It not only was supposed to take images that would allow some vastly greater resolution, but that it could/would allow one to find things in a photo that heretofore weren't previously available (digital generally being assumed to capture more than first glance would suggest). And all of this, in less space, with less power demands.
True?
I never heard any claims quite that grandiose. But there is a big difference between images derived from a conventional mosaic sensor and those produced by a Foveon chip. To explain we have to address the question: "What is a pixel?"
In normal parlance we think of a "pixel" as a picture element (which is where the term came from). But with a mosaic sensor, the only circumstances under which a picture element corresponds to a sensor element is when you're shooting black and white images. Color is a whole other matter. With color images, there is no correspondence between picture elements and sensor elements. The color value of virtually every single picture element in the derived image is a guess.
A very good guess, with the firmware in today's digital cameras. But a guess nonetheless. When you are shooting color with a mosaic sensor, the color value of every single picture element in the final image has to be estimated from the signal level at the surrounding sensor elements, because each sensor element is sensitive to only one of the three primary colors. And the result is never perfect. Very good, but not perfect. Moreover, since the sharpness of the image depends on clearly defined edges determined by different color values, there is price to be paid in sharpness as well as color fidelity.
With the Foveon chip, on the other hand, every single picture element corresponds directly to a sensor element on the light-facing surface of the chip. There is no algorithmic guessing, and therefore no price to be paid in color fidelity or sharpness. But, and there is a but, you'll notice that I mentioned the light-facing surface of the chip. Because, while a 15-megapixel Foveon chip has 15 million sensor elements, they are arranged in three layers, one for each of the primary colors. As a result, the surface area exposed to the incoming light is comprised of 5 million sensor elements, with another 5-million in the second layer, and the final 5-million in the third.
In a DSLR that uses standard lenses, this smaller sensor surface captures a smaller field of view at the focal plane. But because the images are captured directly, without even the slightest loss in quality due to algorithmic guessing, they do indeed enlarge better than would a comparable crop. And when you start talking about the Sigma D1, with 15-megapixels on the light-facing surface of its 45-megapixel Foveon chip, only two thoughts come to mind. One is "Wow!" and the other is, "second mortgage."
K.
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