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Joerg W. Huber, Ian R. L. Davies, Neil Stringer, Chris O'Neil; Station-point violations and their effect on size perception in minimal access surgery. Journal of Vision 2006;6(6):74. doi: 10.1167/6.6.74.
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Curiously, in tele-presence applications such as minimal access surgery there is no control or recommendation over where the surgeon views the monitor from. The retinal image produced by viewing the monitor only replicates the retinal image produced under normal direct viewing if viewed from a single point, the ‘station-point’. If the image is being used to control delicate actions, mis-perceiving the layout could have serious consequences. Experiment 1 assessed the consequences of station-point violation by comparing shape judgments made at the correct station-point and half or double the station-point distance. Isosceles triangles varying in their height to base ratio, drawn on a flat surface, were viewed on a monitor fed by a camera pointing at the surface. This surface with the triangles on was either normal to the camera or inclined away at one of three angles. The subjects' task was to decide which triangle was equilateral. The result was that accuracy of shape judgments declined as the angle of the surface increased, but station-point violation had no effect, implying that observers were compensating for station-point violation. In Experiment 2, additional depth information was provided but although shape judgments were more accurate, the station-point still had no effect. Experiment 3 tested the effect of violating the station-point through viewing the monitor obliquely (45° rotation around the vertical axis). Now, accuracy for oblique viewing was significantly worse than for normal viewing, and in a manner consistent with the optical changes resulting from station-point violation.
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