Less is more: subjective detailedness depends on stimulus size.

Subjective detailedness is the spontaneously perceived overall detailedness of an image. Cursory experience suggests that, for identical objective detailedness, subjective detailedness is higher in small than in large images. While previous studies hint towards a size-dependence of subjective detailedness, they are not conclusive regarding the magnitude, direction and robustness of the effect, in particular in natural images. Subjects performed a two-interval forced choice task, deciding which of a pair of images they perceived as more detailed. We used both natural images and random patterns. One of the images in each pair was scaled down to one third of the linear size of the other, but was otherwise identical. Objective detailedness was adjusted for each image individually via a low-pass filter and the point of subjective equivalence was determined. Depending on the type of image, subjects required the objective detailedness of the larger image to be 0.26-0.48 log units (median values) higher than that of the smaller image for perceiving the same subjective detailedness. This implies that, with equal objective detailedness, smaller images appear more detailed. Our results demonstrate that the effect is sizable and robust across most subjects and across repetitions. It is not readily explained by differences in contrast sensitivity, but may rather have its origin in visuo-cognitive strategies of image evaluation.