We investigated the influence of the medium on the perception of depicted objects and materials. Oil paintings and their reproductions in engravings were chosen because they are vastly distinctive media while having completely identical content. A total of 15 pairs were collected, consisting of 88 fragments depicting different materials, including fabric, skin, wood and metal. Besides the original condition, we created three manipulations to understand the effect of colour (a greyscale version) and contrast (equalised histograms towards both painting and engraving). We performed rating experiments on five attributes: three-dimensionality, glossiness, convincingness, smoothness and softness. An average of 25 participants finished each of the 20 online experimental sessions (five attributes X four conditions). Besides clear correlations between the two media, the differences mainly show in their means (different levels of perceived attributes) and standard deviations (perceived range). In most sessions, paintings depict a wider range than engravings. In addition, it was the histogram equalisation (global contrast) that made the most impact on perceived attributes, rather than colour removal. This suggests that engravers compensated for the lack of colour by exploiting the possibilities of local contrast.

In European painting, a transition took place where artists started to consciously introduce blurred or soft contours in their works. There may have been several reasons for this. One suggestion in art historical literature is that this may have been done to create a stronger sense of volume in the depicted figures or objects. Here we describe four experiments in which we tried to test whether soft or blurred contours do indeed enhance a sense volume or depth. In the first three experiments, we found that, for both paintings and abstract shapes, three dimensionality was actually decreased instead of increased for blurred (and line) contours, in comparison with sharp contours. In the last experiment, we controlled for the position of the blur (on the lit or dark side) and found that blur on the lit side evoked a stronger impression of three dimensionality. Overall, the experiments robustly show that an art historical conjecture that a blurred contour increases three dimensionality is not granted. Because the blurred contours can be found in many established art works such as from Leonardo and Vermeer, there must be other rationales behind this use than the creation of a stronger sense of volume or depth.

Most studies on the perception of style have used whole scenes/entire paintings; in our study, we isolated a single motif (an apple) to reduce or even eliminate the influence of composition, iconography, and other contextual information. In this article, we empirically address two fundamental questions of the existence (Experiment 1) and description (Experiment 2) of style. We chose 48 cut-outs of mostly Western European paintings (15th to 21st century) that showed apples. In Experiment 1, 415 unique participants completed online triplet similarity tasks. Multidimensional scaling (MDS) reached a nonrandom three-dimensional (3D) embedding, showing that participants are able to judge stylistic differences in a systematic way. We also found a strong correlation between creation year and embedding, both a linear correlation with Dimension 2, and a rotational correlation in the first two dimensions. To interpret the embedding further, in Experiment 2, we fitted three color statistics and nine attribute ratings (glossiness, three-dimensionality, convincingness, brush coarseness, etc.) to the 3D perceptual style space. Results showed that Dimension 1 is associated with spatial attributes (Smoothness, Brushstroke coarseness) and Convincingness, Dimension 2 is related to Hue, and Dimension 3 is related to Chroma. The results suggest that texture and color are two important variables for style perception. By isolating the motifs, we could exclude higher levels of information such as composition and context. Interestingly, the results reinforce previous findings using whole scenes, suggesting that style can already be perceived in sometimes very small fragments of paintings.

If two painters paint the same scene, the appearance difference can be referred to as style difference. The distinguishing features result from artists’ use of composition, color, brushstroke etc. We are interested in how people perceive different depiction styles, when they are presented with different levels of information. Whole paintings contain mid-level information (depicted scenes, etc.) and low-level information (brushstroke, colors, etc.). Square cut-outs of single objects contain only low-level information. The same cut-outs in grayscale contain low-level information but without colors. We collected 42 digitized oil paintings as stimuli, the creation years varied from 15th to 21st century, and their location of production varied from southern Spain to the northern Netherlands. All paintings contain at least one apple. We gathered similarity judgement data using a triplet comparison method from three online experiments, where observers were presented the whole paintings (condition 1), square cut-outs of painted apples (condition 2) and the same cut-outs in grayscale (condition 3). 20 observers completed each experiment (60 observers in total). We applied soft ordinal embedding to achieve multidimensional embeddings. We reached a 3D space for condition 1 and 3, and a 4D space for condition 2. Condition 2 has less information than condition 1, but has one more dimension, suggesting that different criteria might be involved. Condition 3 has one less dimension than condition 2, suggesting that color is one of the attributes for style perception judgement. In addition, having the same dimensionality, around 64% of the raw data was in line with the 3D embedding in condition 1 and 58% in condition 3. This difference suggests that although the whole scene and a grayscale cut-out both need three dimensions to describe their style differences, the implicit style criteria for grayscale cut-outs are apparently more ambiguous than those used to judge the whole paintings.

Before the invention of photography, paintings were reproduced in a graphic and linear medium, engravings. To compare material perception across two modalities, paintings and engravings, we conducted two online experiments. We collected 15 pairs of color oil paintings and their engraving reproductions. Then we selected 40 elements from these 15 pairs, including fabric and skin, which resulted in 80 stimuli in total. In experiment 1, we used original (colored) versions for both paintings and engravings. In experiment 2, we used the same stimulus set, but achromatic (luminance only). Two attributes were rated in both experiments: glossiness and softness. 30 observers completed online rating tasks for each attribute in each experiment (120 observers in total). For glossiness, independent of color or black and white versions, engravings scored higher than paintings. In experiment 1, engravings were rated as glossier in 28 out of 40 pairs of variations, with 11 out of these 28 pairs showing significant differences. In experiment 2 (achromatic), engravings scored higher in glossiness than paintings in 33 pairs with 21 pairs showing significant differences. Both numbers increased when colors were removed. For softness, 21 elements in experiment 1 and 29 elements in experiment 2 were judged glossier in engravings than in paintings. Surprisingly, engravings performde well in presenting both gloss and softness. Moreover, when colors were removed, the performance of engravings in conveying glossiness and softness got even better. The increased number of significant cases underscores the robustness of this trend.