Stereograms 4

Stereograms 4

Free-fuse each pair of neighbors. Then you will see a stereoscopic object.

since June 18, 2009

"Overestimation of stereoscopically tilted sides"

When neighboring parallelograms are cross- or uncross-fused, the oblique sides appear to be tilted in depth and appear to be longer than the upper or lower sides, though the oblique lines are actually slightly shorter than the upper or lower sides (If the latter are 100, the former are 93.6 for the left and right parallelograms and 97.3 for the middle one). I think this effect corresponds to the stereoscopic counterpart of the Shepard illusion.

Besides, the upper side appears to be different in size from the lower side, a phenomenon that a farther object appears to be larger than a nearer object even if the physical or retinal sizes are the same. Accordingly, physically parallel oblique sides do not appear to be parallel. I think this effect corresponds to the stereoscopic counterpart of the Leaning Tower illusion.

cf. Thouless, R. H. (1931) Phenomenal regression to the real object. I. British Journal of Psychology, 21, 339-359. <note added February 26, 2011>

"Shepard illusion and overestimation of stereoscopically tilted sides"

Although the oblique lines are actually slightly shorter than the upper or lower sides (If the latter are 100, the former are 93.6 for the left and right parallelograms and 97.3 for the middle one), the oblique sides appear to be the same as or longer than the upper or lower sides. This effect is the Shepard illusion.

When neighboring parallelograms are cross- or uncross-fused, the effect is enhanced. This effect should be regarded as an addition of the Shepard illusion and overestimation of stereoscopically tilted sides.

"Stereoscopic counterpart of the Leaning Tower illusion"

Two trapezoids in each frame are the same shape and size and aligned in parallel, but the right one appears to be tilted more clockwise than the left one (Leaning Tower illusion). This effect is enhanced by binocular stereopsis in that the upper (shorter) side appears to be farther than the lower (longer) side. On the other hand, this effect is decreased by binocular stereopsis in that the upper (shorter) side appears to be nearer than the lower (longer) side.

"Stereoscopic counterpart of the Osa illusion"

The oblique sides in each trapezoid form an angle of 90 degree, which is strongly underestimated by binocular stereopsis. This effect is stronger when the upper (shorter) side appears to be farther than the lower (longer) side. I suggest a close relationship to the "overestimation of stereoscopically tilted sides".

"Osa illusion and its stereoscopic counterpart"

The oblique sides of the contour trapezoid of the central blue road form an angle of 90 degree, which is underestimated (Osa illusion). This effect is enhanced by binocular stereopsis. This effect is stronger when the upper (shorter) side appears to be farther than the lower (longer) side.

Thanks to Idesawa sensei for discussion

"Osa illusion and its stereoscopic counterpart: a Xmas version"

The oblique sides of each trapezoid form an angle of 90 degree, which is underestimated (Osa illusion). This effect is enhanced by binocular stereopsis. This effect is stronger when the upper (shorter) side appears to be farther than the lower (longer) side.

"Stereoscopic counterpart of the Osa illusion: an obuse angle version"

The two oblique edges in a particular right or left side of a hexagon form an angle of 90 degree, which is strongly overestimated by binocular stereopsis.

"Osa illusion: an obuse angle version"

The two oblique edges in a particular right or left side of a hexagon form an angle of 90 degree, which appears to be overestimated.

"Stereogram of the Fraser illusion"

Locat tilts in depth are observed but no global tilt in depth is obtained.

"Transparent Panum's limiting case - Quadruple images"

Quadruple images in depth are observed with binocular fusing. Two by two makes four?

Red circles shows the four depth.

"Transparent Panum's limiting case - Triple images"

Triple images in depth are observed with binocular fusing.

"Transparent Panum's limiting case"

Double images in depth are observed with binocular fusing.

"Demonstration of stereoscopic size constancy"

An object that appears to be nearer with binocular stereopsis appears to be smaller ~~larger~~ than an object that appears to be farther even if the retinal images of these two objects are of the same size.

"Explanation of binocular stereopsis"

When A is nearer to the observer than is B, the image of A is projected to a more temporal part in each retina than that of B (binocular disparity). Based upon this disparity, the brain produces binocular stereopsis of the positions of A and B.

means the right eye in Japanese (probably also in Chinese), whilemeans the left eyes.