Why do objects appear enlarged under water?

Ross, Helen E.; Nawaz, Syed Junaid

doi:10.1590/s0004-27492003000600009

Cited by 14 publications

(5 citation statements)

References 25 publications

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“…However, it is unlikely for accommodation and convergence to be doubly involved in the perception of object size, first in scaling the angular size, and then in scaling the scaled angular size by perceived distance. As Biersdorf et al (1963) and Ross and Nawaz (2003) have shown, angular matching and object matching lead to essentially the same result at close focal distances. It seems likely that as the focal distance gets closer, perceptual decisions regarding the angular size and the object size corresponding to a fixed retinal image become increasingly dependent on the same underlying neural-computational mechanisms.…”

Section: Beyond Emmert's Lawmentioning

confidence: 62%

“…Biersdorf et al (1963) found the same negative slope for the matched size as a linear function of diopter (the reciprocal of the focal distance in meters) regardless of the type of instruction. More recently, Ross and Nawaz (2003) also found that matched size at close viewing distances is no different from the object size regardless of the instructions for angular matching or for object matching. Such results undermine the distinction between the perceived angular size and the perceived object size at close distances, and make the notion of size constancy applicable to A^C micropsia.…”

Section: A^c Micropsia Of Afterimage and Size Constancymentioning

confidence: 93%

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Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

Lou

2007

Perception

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The apparent size of an afterimage viewed from distances between 5 cm and 580 cm was matched to that of a size-adjustable stimulus at a fixed distance (20, 30, 90, and 200 cm). The experiment was conducted under normal indoor illumination with a procedure that facilitated matching for angular size. The matched size was found to increase with focal distance within 1 m and very little beyond 1 m. Similar results were obtained with an equivalent series of real stimuli subtending a constant visual angle. These findings suggest a scaling in perceived angular size in proportion to the oculomotor adjustments for accommodation and convergence. The observations of perceived angular size of the afterimage complement what Emmert's law is meant to describe (perceived object size of the afterimage), even though as the focal distance decreases it may be increasingly difficult to tease out perceived object size and perceived angular size with the matching procedure.

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Section: Beyond Emmert's Lawmentioning

confidence: 62%

Section: A^c Micropsia Of Afterimage and Size Constancymentioning

confidence: 93%

Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

Lou

2007

Perception

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“…This difference can be explained by the hypothesis that objects in water appear larger than those in air by an optical magnification factor of 4/3. Objects in water appear beyond their optical distance and are slightly enlarged in linear size but not in accordance with the size-distance invariance [ 19 ].…”

Section: Discussionmentioning

confidence: 99%

In vitro Comparison of the Mechanical and Optical Characteristics of 5 Disposable Flexible Ureteroscopes

Phromprathum,

Srinualnad,

Leewansangtong

et al. 2024

Urol Int

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Introduction: Disposable (single-use) flexible ureteroscopes are alternatives to reusable ureteroscopes. With their superior surgical efficacy and safety in the presence of upper urinary calculi, disposable ureteroscopes aim to overcome the main limitations of conventional reusable ureteroscopes. However, studies on the performance of the most recently developed models of single-use flexible ureteroscopes are scarce. This study aimed to compare the in vitro performance of several recently introduced, single-use, flexible ureteroscopes. Methods: Five disposable flexible ureteroscopes were tested in vitro to evaluate their mechanical and optical characteristics. To this end, their degrees of deflection, irrigation flow rates, and image qualities were investigated. The models examined were Innovex US31-B12, OTU-100RR, Redpine RP-U-C12, Sciavita SUV-2A-B, and Seplou URS3016E. Their performance was also compared with that of a reusable flexible ureteroscope, Olympus URV-F. Results: The OTU device had the highest degrees of deflection and the smallest loop diameter of the disposable ureteroscopes. The single-use ureteroscopes had identical image resolutions at a distance of 1 cm. The Innovex and Redpine devices had the best color representation. Conclusions: Of the tested disposable ureteroscopes, the OTU device had the best mechanical attributes, given its small loop diameter, high deflection angles, and low irrigation flow loss. As to their optical properties, the resolutions of all 5 single-use models were identical at an image distance of 1 cm.

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“…What happened to the compression of space? Our participants viewed the stimuli in the in-pool condition through a small amount of water (~35 cm) and the display would have been slightly distorted by the refraction of light from the display passing through the participants’ SCUBA goggles, the water column and the transparent viewport of the display 56 , 57 . Figure 5 and the statistical results shown in Supplementary Table S 5 show no significant difference between the in-pool and in-lab data collection sessions in judging the size of a target – no significant magnification or perceptual effects from being submerged were observed.…”

Section: Discussionmentioning

confidence: 99%

Vection underwater illustrates the limitations of neutral buoyancy as a microgravity analog

Bury¹,

Jenkin²,

Allison³

et al. 2023

npj Microgravity

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Neutral buoyancy has been used as an analog for microgravity from the earliest days of human spaceflight. Compared to other options on Earth, neutral buoyancy is relatively inexpensive and presents little danger to astronauts while simulating some aspects of microgravity. Neutral buoyancy removes somatosensory cues to the direction of gravity but leaves vestibular cues intact. Removal of both somatosensory and direction of gravity cues while floating in microgravity or using virtual reality to establish conflicts between them has been shown to affect the perception of distance traveled in response to visual motion (vection) and the perception of distance. Does removal of somatosensory cues alone by neutral buoyancy similarly impact these perceptions? During neutral buoyancy we found no significant difference in either perceived distance traveled nor perceived size relative to Earth-normal conditions. This contrasts with differences in linear vection reported between short- and long-duration microgravity and Earth-normal conditions. These results indicate that neutral buoyancy is not an effective analog for microgravity for these perceptual effects.

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Why do objects appear enlarged under water?

Cited by 14 publications

References 25 publications

Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

In vitro Comparison of the Mechanical and Optical Characteristics of 5 Disposable Flexible Ureteroscopes

Vection underwater illustrates the limitations of neutral buoyancy as a microgravity analog

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