chieved accurately, autofocusing depends on multipattern metering and averaging of the edge characteristics of the image. To be achieved quickly (within a few hundreds, or preferably a few tens of milliseconds), autofocusing depends on highly optimised and highly parallel processing algorithms. The same principle applies to almost all other functions including autoexposure (metering and averaging the luminance characteristics of the image) and colour balancing (metering and averaging the chrominance characteristics of the image. Today, midtier digital cameras can handle capture speeds of at least two frames per second with absolutely no compromise in image capture quality. If camera phones aspire to replace digital cameras, or at least aspire to replace low-end or midtier digital cameras, then they have to provide equivalent functional performance. 8.4.1 Digital Compact and Digital SLR Cameras as a Quality and Functional Performance Reference What does this mean in practice? Let's consider two digital cameras in 2005, one a digital compact, one a digital SLR, both are from the same manufacturer, both are priced at about £700 (Table 8.2). Table 8.2 Digital compact cameras versus digital SLR Specification Digital Compact Digital SLR Resolution (Mpixels) Sensor size (mm) 9 X 6 23.7 X 15.6 ISO range 50-400 200-1600 Lens (35 mm equiv) 35-350 mm 27-105 mm Aperture range F2.8-5.2 F3.5-4.5 Shutter speeds 8-1/3000 S 30-1/8000 S Metering Multisegment (256), centre 3D colour matrix, centre weighted, spot weighted, spot (AF point) EV compensation /2EV in 0.3 EV steps /5 EV in 0.3 or 0.5 EV steps Viewfinder 0.44-inch tft, 235 000 pixels Optical fixed pentaprism Continuous shooting speed 1.2 fps/2.3 fps (display off) 3 fps Continuous shooting capacity 5 shots 4 shots (RAW), 9 shots JPEG fine RAW file processing time O S (up to 5 shots) Start up time AF speed 600 ms 300 ms Battery life 240 shots 400 shots Dimensions 116 X 85 X 121 mm 140 X 111 X 78 mm Weight 600 g 595 g User-Centric Software Note the maximum sensitivity of the 