Monday, June 30, 2008
More than just megapixels—what you need to know about your digital camera’s core component
All Pentax D-SLRs, except the new K20D, use CCD sensors. The K20D features a new 14.6-megapixel APS-C format CMOS sensor codeveloped with Samsung. Much smaller peripheral circuitry increases the photosensitive diode area, and peripheral circuitry handles live-view operation.
The new 14.6-megapixel CMOS sensor in Samsung's GX-20 (and the Pentax K20D-developed by Samsung and Pentax and manufactured by Samsung) features the most megapixels in an APS-C-sized sensor. Large microlenses positioned close to the photodiodes minimize microlens gaps and maximize the light-gathering area, providing excellent performance and allowing for ISOs up to 3200 from the 5.0-micron pixels. An HDR (High Dynamic Range) function increases detail in bright and dark areas.
Sigma's SD14 D-SLR and DP1 compact digital camera are the only current models to feature Foveon's unique X3 "full-color" image sensor. The Foveon sensor takes advantage of the fact that different light wavelengths penetrate silicon to different depths: red, the deepest; green, a bit less; and blue, least of all. Thus, three pixel layers are stacked, the top recording blue light, the middle one, green, and the bottom one, red. The advantage of this system is that every pixel site records every color, so no colored filter array is needed over the pixels, no interpolation of missing colors is needed and no image-softening anti-aliasing filter is needed.
After starting its D-SLR program (in part using technology acquired from Konica Minolta) with its own CCD sensors, Sony has put a new Sony Exmor CMOS unit in its top-of-the-line DSLR-A700 model. The 12.2-megapixel Exmor features on-sensor A/D conversion and dual before-and-after-conversion noise reduction. The sensor responds well to Sony's Dynamic Range Optimizer, which allows users to adjust the dynamic range to suit the scene. Sony's low-priced DSLR-A350 has the highest-resolution CCD sensor (14.2 megapixels) in the category in a 35mm form-factor D-SLR. Sony is currently working on a 24.6-megapixel full-frame Exmor CMOS sensor for its flagship D-SLR model due later this year.
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