It’s a significantly improved version of the Multi-CAM 900 autofocus module found in the Nikon D100, D70, and D50 digital SLR (DSLR) cameras. Where the Multi-CAM 900 was limited to Single Area, Dynamic Area, and Dynamic Area with Closest Subject Priority modes, the Multi-CAM 1000 adds another AF mode called Group Dynamic. This mode gives you finer control over things like sports photography, macro focusing, and selective area AF.
While the Multi-CAM 900 had five AF sensors, the Multi-CAM 1000 gives us 11. It is very similar to the 11-sensor arrangement in the flagship Nikon D2x Multi-CAM 2000 system. So, you can expect professional-level performance from Multi-CAM 1000 in the D90.Why is it called Multi-CAM 1000? The number 1000 represents the approximate number of CCD contrast-sensing elements in the autofocus system. With so many elements, it will autofocus in low to high light levels and at high speeds.
A unique feature of the Multi-CAM 1000 in the Nikon D90 is the ability to combine the 11 sensors into a 7-AF areas wide-array arrangement. This gives you the ability to better follow moving subjects like flying birds, race cars, or airplanes.