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

Automatic Lighting Correction

Some scenes contain too great a brightness range for a normal exposure to record detail throughout. Automatic lighting correction helps address this. Auto lighting correction comes under various names: Auto Lighting Optimizer and Highlight Tone Priority (Canon), Active D-Lighting (Nikon), Shadow Adjustment Technology (Olympus), Dynamic Range Expansion (Pentax) and Dynamic Range Optimizer (Sony), for example.

Basically, these systems adjust exposure and in-camera processing to retain more detail in bright and dark areas. Sony (and presumably newer Nikon) D-SLRs work on the RAW data from the sensor before it becomes an image and don't suffer the problems of working on compressed image data. This requires lots of processing power and can slow the shooting rate or limit the number of shots that can be made in a continuous burst, but provides very effective results.

With some systems, you can choose among several strength settings or let the camera make the adjustments automatically. You also can switch automatic lighting correction off when it's not needed or when shooting speed is a priority.

The new Pentax K-7 has an HDR feature that captures three images, then combines them in-camera to bring out detail in all areas of the image.

Panasonic's Lumix GH1 is one of many cameras with subject-tracking AF to follow a moving subject.

Subject Tracking

AF SLRs have long been able to track moving subjects (some more effectively than others) through their continuous AF mode. In order to compensate for the small distance a subject moves during the brief span between the moment you fully depress the shutter button to make the exposure and the moment the exposure is actually made, most AF SLRs feature predictive AF, in which the AF system calculates the subject's predicted position at the instant of exposure (based on successive focus readings and the assumption the subject will continue to move in the direction and at the speed it was moving when those readings were taken).

Minolta came up with Multi-Dimensional Predictive AF many years ago, which could even handle subjects that changed speed or direction—pretty amazing. Sony now incorporates that in its D-SLRs (having acquired Minolta's D-SLR technology when Minolta left the camera market). Other manufacturers are a bit tight-lipped about the inner workings of their AF systems, but today's predictive autofocusing works very accurately, regardless of brand.

Nikon's new D5000 can "memorize" brightness and color information from a selected area of the subject and track the subject as it moves across the frame, even if it momentarily leaves the frame. When the subject reenters the frame, the camera will pick it up and, assuming you have the shutter button depressed halfway, focus on it. Note that autofocusing doesn't occur while the camera is tracking the subject with this feature.
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