Sunday, August 23, 2009

Smart Cameras

Powerful processors and advanced technology give today’s digital cameras some remarkable features
By Mike Stensvold Published in SLRs
Smart Cameras

Live View Multiexposure

Multiple-exposure capability—the ability to make several exposures on a single frame of film or in a single digital image—has been around for years. But even this old favorite has seen a new wrinkle of late. For example, the Olympus E-30 and E-620 let you display an already-shot image on the LCD monitor in Live View mode and then use it as a guide for superimposing a second image. This makes it easy to position both images precisely.


Sigma's D-SLRs and digital compact cameras like the new DP2 don't have a lot of the bells and whistles—they're straightforward cameras with easy-to-use (and easy-to-figure-out) controls. What they do have is the unique Foveon full-color-capture CMOS image sensor and a TRUE (Three-layer Responsive Ultimate Engine) processor designed to get the most from it.

Conventional CCD and CMOS sensors don't see colors; they just see brightnesses. In order to provide color information, a grid of colored filters is positioned over the sensor, so that each pixel is covered by a red, green or blue filter. How do the pixels get color information for the other two primary colors? From the neighboring pixels, via complex interpolation using proprietary algorithms.

Canon's peripheral illumination correction, available on the EOS 5D Mark II, EOS 50D and new EOS Rebel T1i, automatically adjusts for light falloff near the corners of the frame for supported lenses.
The Foveon sensor used in Sigma digital cameras takes advantage of the fact that different light wavelengths penetrate silicon to different depths, in effect "stacking" three pixel layers—a top one that records blue light, a middle one that records green and a bottom one that records red. Thus, every pixel site actually does record all three primary colors of light, no interpolation (and no image-softening anti-aliasing filter) required. The result is sharp images with accurate colors and no "artifacts."

Automatic Lens Correction

Two major problems inherent in camera lenses are vignetting and chromatic aberrations. Vignetting means the center of the image is brighter than the edges and especially the corners, due to the light falloff. Some recent D-SLRs are programmed to compensate for this light falloff automatically when a lens in the camera's onboard database is being used.

Among other things, chromatic aberrations cause the infamous "purple fringing" around subject edges in high-contrast images. A number of recent D-SLRs automatically compensate for this when you use a lens that's included in the camera's onboard lens database. These cameras come with a number of popular lenses in the database, and you can add others via supplied software.

Some cameras—Nikon's new D5000 and Pentax's new K-7, for example—can even correct for barrel and pincushion distortion as you shoot with wide-angle and long lenses.

Yet to Come

This is just a sampling of features you can use today; there are lots more to come. Many of the technologies and components necessary to advance digital imaging are just starting to appear.

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