Mahdi Nezamabadi

Effect of image size on the color appearance of image reproductions using colorimetrically calibrated LCD and DLP displays

— Archiving images of cultural heritage based on spectral imaging techniques is an active research area in imaging science. Original and reproduced art are usually viewed under quite different viewing conditions. One of the interesting differences in viewing condition is size difference. This leads to different surrounds and adaptation states. In order to investigate the effect of size in color perception of rendered images, a visual experiment was conducted using a colorimetrically characterized digital projector and LCD. An image was rendered and projected on the screen. The same image was processed using various algorithms followed by rendering for the LCD. These LCD rendered images, by definition, were considerably smaller than the projected image. Using a paired-comparison method, the effect of image size was investigated using a colorimetric image of Georges Seurats, “Sunday Afternoon on the Island of La Grande Jatte — 1884.” The image rendered for an LCD with a linear increase in lightness resulted in a closer match to the image projected on screen than an original colorimetrically rendered image and was perceived as a more accurate reproduction than the majority of algorithms tested.

An investigation of the effect of image size on the color appearance of softcopy reproductions using a contrast matching technique

Many art objects have a size much larger than their softcopy reproductions. In order to develop a multiscale model that accounts for the effect of image size on image appearance, a digital projector and LCD display were colorimetrically characterized and used in a contrast matching experiment. At three different sizes and three levels of contrast and luminance, a total of 63 images of noise patterns were rendered for both displays using three cosine log filters. Fourteen observers adjusted mean luminance level and contrast of images on the projector screen to match the images displayed on the LCD. The contrasts of the low frequency images on the screen were boosted while their mean luminance values were decreased relative to the smaller LCD images. Conversely, the contrast of projected high frequency images were reduced for the same images on LCD with a smaller size. The effect was more pronounced in the matching of projected image to the smaller images on the LCD display. Compared to the mean luminance level of the LCD images, a reduction of the mean luminance level of the adjusted images was observed for low frequency noise patterns. This decrease was more pronounced for smaller images with lower contrast and high mean luminance level.