One of the primary jobs of visual perception is to build a three-dimensional representation of the world around us from our flat retinal images. These are a rich source of depth cues but no single one of them can tell us about scale (i.e., absolute depth and size). For example, the pictorial depth cues in a (perfect) scale model are identical to those in the real scene that is being modelled. Here we investigate image blur gradients, which derive naturally from the limited depth of field available for any optical device and can be used to help estimate visual scale. By manipulating image blur artificially to produce what is sometimes called fake tilt shift miniaturization, we provide the first performance-based evidence that human vision uses this cue when making forced-choice judgements about scale (identifying which of an image pair was a photograph of a full-scale railway scene, and which was a 1:76 scale model). The orientation of the blur gradient (relative to the ground plane) proves to be crucial, though its rate of change is less important for our task, suggesting a fairly coarse visual analysis of this image parameter.
Bibliographical noteCopyright: © 2023 Meese et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by research grant EP/H000038/1 from the Engineering and Physical Sciences Research Council awarded to Tim Meese and Mark Georgeson. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Data Availability: The raw data, code and stimuli for this study can be found on the OSF repository at: https://doi.org/10.17605/OSF.IO/4K2XP
- Depth Perception
- Visual Perception