Size And Speed
Also shared with the D90 is the ‘APS-C’ size – or DX format in Nikonese – CMOS-type sensor with a total pixel count of 12.9 million. Naturally, there will be comparisons with the 500D’s resolution of 15.5 megapixels, but more isn’t necessarily better if it involves smaller-sized pixels compromising image quality and, besides, the roughly 2.5 MP difference isn’t going to translate into much in real terms.
The D5000’s sensor’s effective pixel count of 12.3 MP delivers a maximum image size of 4288x2848 pixels and, with JPEG capture, there’s a choice of two smaller sizes and three compression levels which Nikon annotates as 1:4, 1:8 and 1:16. RAW files are captured as 36-bit NEFs. RAW+JPEG capture is possible with any size/ quality compressed file attached. The sensitivity range is equivalent to ISO 200 to 3200 with ‘boost’ settings either side for ISO 100 and 6400.
This CMOS sensor is mated with a dedicated version of Nikon’s ‘Expeed’ high-speed image processor, enabling a host of number-crunching features such as scene recognition and face detection AF plus continuous shooting at up to a nippy 4.0 fps (only marginally slower than the D90). Sensor cleaning is performed via ultrasonic vibration of the low-pass filter (LPF) on the front of the image module, but Nikon works to minimise the amount of dust actually getting that far via a vent arrangement which is designed to create a more vigorous airflow inside the mirror box. Active cleaning is performed automatically whenever the camera is switched on or off, but can also be manually activated. Incidentally, image stabilisation in the Nikon D-SLR world is done optically via VR-equipped lenses and the D5000 is packaged with the 18-55mm VR standard zoom (although it can also be purchased as a camera body only should you wish to specify another lens).
To keep it compact, the D5000 has a penta-mirror type optical viewfinder – while the D90 has a full pentaprism which gives a higher magnification – but it has an adjustable-angle LCD monitor screen to maximise the functionality of live view.
The tilt/swing monitor is a first for a Nikon D-SLR and, unusually, it pivots from the base of the camera rather than from the side. However, like any adjustable monitor, it can be folded away with the screen facing inward which protects it most effectively during carriage or storage.
Live view on the D5000 is achieved conventionally by locking up the reflex mirror and opening the shutter which both must then be recycled to enable an exposure to commence. However, Nikon has abandoned the even clunkier ‘Hand Held’ mode for autofocusing in live view (which used the conventional AF sensors) so the D5000 has to rely entirely on contrast detection measurements derived from the imaging sensor. This system is pretty slow too, although there’s a choice of face-priority and wide-area modes (in reality, not actually all that wide) plus a new tracking capability which has the potential to be useful with active subjects such as children or pets… even if the instruction manual does warn “Some time may be required for the camera to initiate focus” which could well defeat the purpose of the facility anyway. Consequently, in many situations focusing manually is the best option with live view, especially as part of the subject can be magnified (by up to about 6.7x on the D5000) to enable quite precise fine-tuning.