Effect of smartphone camera settings in colorimetric measurements under controlled illumination

Abstract

Smartphone based point-of-care diagnostics can be a viable alternative for lab-based methods in low resource settings. However smartphone applications for quantification of colorimetric tests are not robust enough and lack field portability as they require external add-on device to mitigate ambient lighting conditions. To make the system accessory free, we need some features which do not change with ambient light conditions. However, camera ISP system adjust itself to give best image by compromising spectral changes. In this study, we investigated smartphone camera settings; ISO and Focus to study the effect of these settings on colorimetric values in controlled lighting conditions. A total of 198 images were acquired using smartphone, where ISO and focus, were changed manually in different lighting conditions; 3 different color temperature and 10 focus points. It was observed that “Hue” parameter of HSV color space and “a” parameter of CIEL*a*b color space depicts least variation with lighting and ISO variation. Also, colorimetric values change with the focus on strip. Therefore, ISO and Focus settings of smartphone should be taken into account for accurate colorimetric estimation.