Abstract
An image of a scene depends on both the physical attributes of the surfaces it depicts and the characteristics of the lens used to capture it. The visual system can often tell when an image has been captured using a shallow depth of field or a specific focal length, and variation in image ‘defocus’ blur has been studied extensively as depth cue. The tilt-shift effect demonstrates how depth of field manipulations can induce strong differences in perceived scene scale, but the image features used by the visual system to differentiate defocus from other sources of image blur are unknown. Here, we show that misinterpretation of image blur can cause depth of field manipulations to induce illusory distortions in perceived shape and material, and reveal the conditions that produce this effect. We manipulated the depth of field and focal length used to render images of 3D surfaces varying in relief height and specularity, and measured differences in perceived surface gloss and depth of field (using paired comparison tasks) and perceived 3D shape (using the gauge figure task). We found that depth of field manipulations that preserved the sharpness of a surface’s occluding edge led to larger changes in perceived gloss and shape, and smaller changes in perceived depth of field, than conditions where the occluding edge was blurred by defocus. These differences were also larger for more specular surfaces. Our results reveal that changes in the occluding edges of surfaces are important cues in the perception of shallow depth of field, and that defocus blur can be misattributed to changes in specular roughness or shading gradients when these cues are absent.
Meeting abstract presented at VSS 2015