Figure 2. Yardstick which lines up the perceived freshness scores of each image according to their scores on a one-dimensional line.

Each vertical gray line on the yardstick indicates the perceived freshness score (PFS) of each image. Distance from the left edge of the scale to each vertical gray line depicts the score size of each image: an image indicated by a vertical gray line positioned nearer the right side was perceived as fresher than that nearer the left side. Labels under the images indicate the individual identification index and degradation time of each image.