A commentary on ‘Amplitude spectra of natural images’

2015 ◽  
Vol 35 (6) ◽  
pp. 628-630
Author(s):  
David J. Tolhurst
Keyword(s):  
Natural Images ◽  
Amplitude Spectra

Contrast Adaptation and the Spatial Structure of Natural Images

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 174-174
Author(s):  
M A Webster ◽  
O H MacLin ◽  
A L Rees ◽  
V E Raker
Keyword(s):  
Selective Adaptation ◽  
Natural Images ◽  
Spatial Frequencies ◽  
Outdoor Scenes ◽  
Amplitude Spectra ◽  
Contrast Pattern ◽  
Biased Perception ◽  
Face Adaptation ◽  
Contrast Thresholds ◽  
Human Faces

Contrast (pattern-selective) adaptation influences perception by adjusting sensitivity to the prevailing pattern of stimulation. We asked how the state of adaptation might depend on the patterns of spatial contrast typical of the natural visual environment. In one set of experiments, we examined whether adaptation to the characteristic amplitude spectra of natural images (which tend to decrease with frequency as 1/f) induces characteristic changes in contrast sensitivity. Contrast thresholds and suprathreshold contrast matches were measured after adaptation to random samples from an ensemble of images of natural outdoor scenes, or synthetic images formed by filtering the amplitude spectra of noise over a range of slopes. Adaptation differentially reduced sensitivity at low to medium spatial frequencies, but losses were not strongly dependent on the slope of the adapting spectra. In a second set of experiments, we examined the figural aftereffects induced by adaptation to naturalistic stimuli, by adapting and testing with images of human faces, for which small configural changes are highly discriminable. Observers adapted to frontal-view images of faces that were distorted by local expansions or contractions about the centre, and then adjusted distortions in test images to try to select the original face. Adaptation strongly biased perception in a direction opposite to the adapting distortion, with strongest aftereffects when test and adapting stimuli were derived from the same face image. Our results suggest that adaptation to the stimuli encountered in the course of normal viewing may exert ubiquitous and selective influences that are important in characterising the normal operating state of the visual system.

Discrimination of Changes in the Slopes of the Amplitude Spectra of Natural Images: Band-Limited Contrast and Psychometric Functions

Perception ◽  
1997 ◽  
Vol 26 (8) ◽  
pp. 1011-1025 ◽  
Author(s):  
David J Tolhurst ◽  
Yoav Tadmor
Keyword(s):  
Spatial Frequency ◽  
Discrimination Task ◽  
Spatial Scales ◽  
Natural Images ◽  
Natural Scenes ◽  
Local Contrast ◽  
Frequency Bands ◽  
Amplitude Spectra ◽  
Lower Frequency Band ◽  
Band Limited

Thresholds were measured for discriminating changes in the slopes of the amplitude spectra of stimuli derived from photographs of natural scenes and from random-luminance patterns. The variety and magnitudes of the thresholds could be explained by a model based on the discrimination of the changes in band-limited local contrast. Different spatial scales of local contrast (or different spatial-frequency bands of about 1 octave) were implicated for different reference spectral slopes; the model implicated a lower frequency-band for stimuli with shallower amplitude spectra. The implications of the model were tested experimentally by using stimuli in which the spectra were changed within restricted spatial-frequency bands. When the amplitude spectra of the test and reference stimuli differed only within the implicated frequency bands, thresholds were affected little. However, when the test and reference spectra differed at all frequencies except those in the implicated bands, the thresholds were elevated markedly. The forms of the psychometric functions for the discrimination task were entirely compatible with the hypothesis that the task relies upon the ability to discriminate changes of contrast. The Weibull functions fitted to the data had slope parameters (β) in the range 1 to 3, compatible with discrimination of low (but suprathreshold) contrasts.

scholarly journals Amplitude spectra of natural images

2007 ◽  
Vol 12 (2) ◽  
pp. 229-232 ◽  
Author(s):  
D. J. Tolhurst ◽  
Y. Tadmor ◽  
Tang Chao
Keyword(s):  
Natural Images ◽  
Amplitude Spectra

Prediction of the Helmholtz-Kohlrausch Effect for Natural Images Using a Correction Function

2019 ◽  
Vol E102.A (9) ◽  
pp. 1217-1224
Author(s):  
Yuki HAYAMI ◽  
Daiki TAKASU ◽  
Hisakazu AOYANAGI ◽  
Hiroaki TAKAMATSU ◽  
Yoshifumi SHIMODAIRA ◽  
...  
Keyword(s):  
Natural Images ◽  
Correction Function
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