Comparison of digital image quality obtained from different image sensors

Abstract

Nowadays, digital still camera is worldwide accepted as a significant input device. Image sensors play a vital role for the image quality of digital still cameras. The purpose of this research is to evaluate and compare the digital image quality generated from four different image sensors, i.e. CCD, Super CCD, CMOS and FOVEON X3, in terms of image resolution, tone reproduction, color reproduction and graininess/noise. For image resolution, visual resolution and spatial frequency response (SFR) were measured and compared. For tone reproduction, comparisons of tone reproduction curve of image pixel values were performed. For color reproduction, Delta E*[subscript ab] (color error of Macbeth color checker) were measured and compared. With different kinds of graininess/noise including dark current noise, amplifier noise, thermal noise and shot noise, the standard deviations of image pixel value at middle gray were measured and compared. For the image resolution measurement, Fuji S2pro (Super CCD) had highest absolution and extinction resolution while Sigma SD9 (Foveon X3) had the highest SFR, which represents the best contrast. For the tone reproduction measurement, Canon D60 (CMOS) had the highest dynamic range which means that CMOS could best capture the bright and dark areas. For the color reproduction measurement with all color tones analysis, Nikon D100 (CCD) had lowest color error, which means that CCD could most capture the natural color in all color. For the graininess/noise measurement, Canon D60 (CMOS) had the lowest amplifier noise in luminous channel at ISO100 while Fuji S2pro (Super CCD) had the lowest amplifier noise in luminous channel at ISO200-ISO1600. It means that CMOS had high capacity in providing an accurate image signal at ISO100 while Super CCD was better at ISO200-ISO1600. Nevertheness, the effectiveness of each image sensor could be differently among the management program of each camera.