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Guido Maiello, Manuela Chessa, Fabio Solari, Peter Bex; The Contribution of Perspective, Blur and Disparity to Depth Perception in Natural Vision. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2662.
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© ARVO (1962-2015); The Authors (2016-present)
Natural scenes contain multiple sources of depth information. However, the relative contribution of these alternative cues is not well understood under natural conditions. When these cues are not accurately simulated in computer generated 3 dimensional scenes, observers can experience visual fatigue, nausea and diplopia. We examine depth perception in real images with natural variation in perspective, blur and binocular disparity.
Image patches subtending 8 degrees of visual angle were extracted from light field photographs of natural scenes taken with a Lytro camera that simultaneously captures up to 12 focal planes. When accommodation at any given plane was simulated, the correct defocus blur and stereoscopic disparity at other depth planes was extracted from the stack of focal plane images. Depth information from geometric cues, relative blur and stereoscopic disparity were independently introduced into depth images. In a 2AFC paradigm with feedback, four observers identified the closer of two stimuli presented concurrently.
Depth discrimination thresholds were lowest when geometric and stereoscopic disparity cues were both present. Depth order discrimination was not possible with defocus blur alone and the addition of blur cues impaired geometric thresholds by reducing the contrast of geometric information at high spatial frequencies. When blur cues were introduced along with geometric and disparity cues, they did not noticeably impair thresholds, and appeared to compensate the perceptual bias towards the far plane previously induced by disparity.
Light field photographs are a useful tool to quantify how naturally-occurring cues contribute to depth perception. Correct defocus blur diminishes visual fatigue while viewing stereoscopic stimuli (Hoffman, et al (2008) JoV 8(3), 33,1-33,30) and should therefore not be discarded in 3D images. Here we show that defocus cues alone impair fine depth perception near the plane of fixation, but might be beneficial if used in conjunction with stereoscopic disparity.
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