As shown in Fig. 3(b), there are significant deviations from the designed yellow intensity using both the smartphone and digital camera. Using either a digital camera or a smartphone, the yellow intensity was overestimated at low values and saturated at a value of 55–60%. In fact, the picture captured by using a scanner provides yellow intensities that are more consistent with the preset values (up to 65%). Reducing the illumination levels using the scanner can correct such deviations even further,while the correction of camera captured images is rather difficult. In addition, there is no need to modulate the aperture and focal length when using a scanner to capture images, hence the flatbed scanner is the ideal tool for colorimetric analysis in the present study.