Signal to Noise Ratio and Visual Noise of Mobile Phone Cameras

Recently, ISO standard 15739:2013 revealed the first official visual noise metrics. Until now, signal to noise ratio (SNR) has been used the most as the noise measurement metric for digital cameras, but according to several research studies it does not represent the visual perception of noise included in images. This article investigates the differences between SNR based noise measurements and visual noise measurements when real mobile phone cameras are measured. The work contains the following tasks. Firstly, the improvements between old and new standards are detailed. Secondly, the noise measurements are executed, testing 20 mobile phones using three different light environments. Finally, the results are compared between different noise measurement algorithms and conclusions are drawn. The result of this work gives detailed noise measurement results for mobile phone camera systems on the market. Total and visual noise metrics are measured, also corresponding ISO speed and exposure parameters are stored and correlations between noise levels and parameters are calculated. The differences between noise metrics are summarized and perceptual inspection is made of the images which have clear differences between total and visual noise. (C) 2015 Society for Imaging Science and Technology.