Luminance changes within a scene are ambiguous; they can indicate reflectance changes, shadows, or shading due to surface undulations. How does vision distinguish between these possibilities? When a surface painted with an albedo texture is shaded, the change in local mean luminance (LM) is accompanied by a similar modulation of the local luminance amplitude (AM) of the texture. This relationship does not necessarily hold for reflectance changes or for shading of a relief texture. Here we concentrate on the role of AM in shape-from-shading. Observers were presented with a noise texture onto which sinusoidal LM and AM signals were superimposed, and were asked to indicate which of two marked locations was closer to them. Shape-from-shading was enhanced when LM and AM co-varied (in-phase), and was disrupted when they were out-of-phase. The perceptual differences between cue types (in-phase vs out-of-phase) were enhanced when the two cues were present at different orientations within a single image. Similar results were found with a haptic matching task. We conclude that vision can use AM to disambiguate luminance changes. LM and AM have a positive relationship for rendered, undulating, albedo textures, and we assess the degree to which this relationship holds in natural images. [Supported by EPSRC grants to AJS and MAG].
|Publication status||Unpublished - 2006|
|Event||29th European Conference on Visual Perception - St Petersburg , Russian Federation|
Duration: 20 Aug 2006 → 25 Aug 2006
|Conference||29th European Conference on Visual Perception|
|Period||20/08/06 → 25/08/06|
Bibliographical noteAbstract published in ECVP 2006 Abstract Supplement, Perception, 35(Suppl. S), p. 227. ISSN 0001-4966
- luminance changes
- indicate reflectance changes
- surface undulations
- local mean luminance
- local luminance amplitude
- disambiguate luminance changes
Schofield, A. J., Georgeson, M. A., Hesse, G., Rock, P. B., & Yates, T. A. (2006). The role of local luminance amplitude in the interpretation of shape-from-shading in textured surfaces. Paper presented at 29th European Conference on Visual Perception, St Petersburg , Russian Federation.