Summary
Visual acuity was measured with grating test patterns that had areas of 1, 5 or 25 cm2. When subjects were instructed to adjust the viewing distance so that all parts of the grating appeared clear, the smaller gratings were visible at greater distances. However, when subjects were asked to adjust the distance so that they could identify the orientation of the grating, stimulus area had little effect on acuity. The apparent loss of acuity for larger test patterns that was found when the first criterion was used resembles the loss of acuity in the parafoveal retina, and therefore is probably a result of requiring the subject to use peripheral regions of his retina, rather than a consequence of the phenomenal spreading of the lines in small gratings.
Zusammenfassung
Die Sehschärfe wird mit Gittern mit einer Fläche von 1 bis 25 cm2 gemessen. Wenn die Vpn als Kriterium die deutliche und klare Erkennbarkeit des Gitters verwenden, werden die kleineren Gitter bei größeren Entfernungen gesehen. Wenn jedoch die Vpn nur die Richtung der Gitterstreifen angeben sollten, wird die Sehschärfe von der Fläche des Gitters unabhängig. Die schembare Abnahme der Sehschärfe beim ersten Kriterium ist der Abnahme der Sehschärfe zur Peripherie hin ähnlich und ergibt sich vermutlich durch die Mitwirkung extra-fovealer Bereiche und nicht durch die scheinbar größere Schärfe kleinerer Gitter.
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Supported by the J. McKeen Cattell Fund. We are grateful to Dr. G. Vicario for extensive advice in replicating his experiment, to Dr. Donald Laming for assistance in the statistical analysis, to Dr. J. D. Mollon for critically reading the manuscript, and to Professor O. L. Zangwill for providing facilities.
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Chapman, F.A., Cavonius, C.E. The influence of stimulus area on visual acuity effect of observer criterion. Psychol. Forsch. 36, 329–334 (1974). https://doi.org/10.1007/BF00424570
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DOI: https://doi.org/10.1007/BF00424570