Nikon updates its entry-level dSLR with the addition of video capture, new processing algorithms, and the de rigeur bump in resolution. The D3100 adds HD video capture with continuous autofocus. Continuous AF is unusual in dSLRs, but for good reason; the focusing mechanisms in the lenses are generally too noisy and an unwelcome addition to your soundtrack. This remains true for Nikon's solution, and without a mic input, you really have no way around it. Consider it a tradeoff. The camera does have a direct-access button for movie mode rather than shunting it off to the mode dial.
Here are some basic comparisons with Nikon's other current entry-level models (tables updated with more specs):
Nikon D3100 Nikon D5000
Sensor (effective resolution) 10.2-megapixel CCD 14.2-megapixel CMOS 12.3-megapixel CMOS 23.6 x 15.8.mm 23.6 x 15.8mm23.1 x 15.4mm 23.6 mm x 15.8mm Sensitivity range ISO 100 - ISO 3200 ISO 100 (expanded)/200 - ISO 3200/12,800 (expanded) ISO 100 (expanded)/200 - ISO 1600/3200 (expanded Continuous shooting 3fps n/a raw/n/a JPEG 3fps n/a 4 fps 9 raw/100 JPEG (medium/fine) Viewfinder magnification/effective magnification 95% coverage 0.80x/0.53x 95% coverage 0.80x/0.53x 95% coverage 0.78x/0.52x Autofocus 11-pt AF center cross-type 11-pt AF center cross-type 11-pt AF center cross-type to f5.6 Shutter speed 1/4000 to 30 secs; bulb; 1/200 sec x-sync 1/4000 to 30 secs; bulb; 1/200 sec x-sync 1/4000 to 30 secs; bulb; 1/200 sec x-sync Metering 420-pixel 3D color matrix 420-pixel 3D color matrix 420-pixel 3D color matrix Live View Yes No Yes Yes Video No 1080/24p; 720/30p AVCHD MOV 720/24p LCD size 3 inches fixed 230,000 dots 3 inches fixed 230,000 dots 2.7 inches articulated 230,000 dots Wireless flash Yes Yes No Battery life (CIPA rating) 500 shots n/a shots 510 shots Dimensions (inches, WHD) 5.0 x 3.8 x 2.5 4.9 x 3.8 x 2.9 5.0 x 4.1 x 3.1 Body operating weight (ounces) 18.8 17 (est) 21.6 Mfr. Price n/a n/a $629.95 (body only) $549.95 (with 18-55mm lens) $699.95 (with 18-55mm lens) $699.99 (est, with 18-55mm lens) n/a n/a n/a Ship date July 2009 September 2010 April 2009
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