System implications of implementing white balance on consumer digital cameras

Abstract

In consumer digital cameras, some of the primary tasks in the image capture data path include automatic focus, automatic exposure determination and auto-white balance (AWB). There are numerous algorithms used in implementing these tasks--auto-focus is implemented using maximum contrast, ranging or sonar; white balance using color gamut determinations and `gray value estimations', and auto- exposure using scene evaluations. We evaluate the system implications of implementing one of these tasks, namely white balance on an embedded system--a digital camera. There include, among other things, design approach, power consumption, software vs. hardware implementation and microprocessor vs. ASIC implementation. Commercially available digital cameras and their choice of AWB implementation are discussed where appropriate. Such an evaluation will assist, we hope, anyone designing or building a digital camera sub-system.