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The effect of background and illumination on color identification of real, 3D objects.

Allred SR, Olkkonen M - Front Psychol (2013)

Bottom Line: As in 2D scenes, we found relatively high but imperfect stability of color judgments under an illuminant shift.In contrast to 2D scenes, we found that background had little effect on average color judgments.Taken together, these results suggest that in real 3D scenes with ample cues to object segregation, the addition of a background may improve stability of color identification.

View Article: PubMed Central - PubMed

Affiliation: COVI Research Lab, Department of Psychology, Rutgers - The State University of New Jersey Camden, NJ, USA.

ABSTRACT
For the surface reflectance of an object to be a useful cue to object identity, judgments of its color should remain stable across changes in the object's environment. In 2D scenes, there is general consensus that color judgments are much more stable across illumination changes than background changes. Here we investigate whether these findings generalize to real 3D objects. Observers made color matches to cubes as we independently varied both the illumination impinging on the cube and the 3D background of the cube. As in 2D scenes, we found relatively high but imperfect stability of color judgments under an illuminant shift. In contrast to 2D scenes, we found that background had little effect on average color judgments. In addition, variability of color judgments was increased by an illuminant shift and decreased by embedding the cube within a background. Taken together, these results suggest that in real 3D scenes with ample cues to object segregation, the addition of a background may improve stability of color identification.

No MeSH data available.


(A) Color constancy indices in the illumination condition. Each bar shows the average color constancy index for one cube, with perfect constancy indicated by the red horizontal line. Indices are modified-Brunswick ratios (see Materials and Methods) averaged across observers. Error bars are s.e.m across observers; the average number of observers per cube was 12. (B) Average constancy indices in the joint condition (with background; y-axis) and the illumination condition (no background; x-axis). Black diagonal line indicates no effect of background. Bar height (A) and symbol color (B) approximate apparent cube color.
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Figure 5: (A) Color constancy indices in the illumination condition. Each bar shows the average color constancy index for one cube, with perfect constancy indicated by the red horizontal line. Indices are modified-Brunswick ratios (see Materials and Methods) averaged across observers. Error bars are s.e.m across observers; the average number of observers per cube was 12. (B) Average constancy indices in the joint condition (with background; y-axis) and the illumination condition (no background; x-axis). Black diagonal line indicates no effect of background. Bar height (A) and symbol color (B) approximate apparent cube color.

Mentions: As with the data for the individual cubes (Figure 4), average color constancy across all cubes under an illumination shift, shown in Figure 5, was generally high but imperfect. To quantify the degree of constancy, it is standard to compute a color constancy index. Such indices seek to frame the data with respect to their position between the constancy and no-constancy predictions, where 1 indicates perfect constancy, 0 indicates a complete failure of constancy, and indices greater than 1 indicate that observers overcompensated for the illuminant shift. From the constancy predictions (illustrated for the four cubes in Figure 4), we computed such an index (see Materials and Methods). Briefly, the color constancy prediction was derived using the assumption that color constant observers would choose the same paint chips in the baseline condition as in the illumination condition; that is, their matches would reflect consistency in surface reflectance, rather than chromaticity.


The effect of background and illumination on color identification of real, 3D objects.

Allred SR, Olkkonen M - Front Psychol (2013)

(A) Color constancy indices in the illumination condition. Each bar shows the average color constancy index for one cube, with perfect constancy indicated by the red horizontal line. Indices are modified-Brunswick ratios (see Materials and Methods) averaged across observers. Error bars are s.e.m across observers; the average number of observers per cube was 12. (B) Average constancy indices in the joint condition (with background; y-axis) and the illumination condition (no background; x-axis). Black diagonal line indicates no effect of background. Bar height (A) and symbol color (B) approximate apparent cube color.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3823087&req=5

Figure 5: (A) Color constancy indices in the illumination condition. Each bar shows the average color constancy index for one cube, with perfect constancy indicated by the red horizontal line. Indices are modified-Brunswick ratios (see Materials and Methods) averaged across observers. Error bars are s.e.m across observers; the average number of observers per cube was 12. (B) Average constancy indices in the joint condition (with background; y-axis) and the illumination condition (no background; x-axis). Black diagonal line indicates no effect of background. Bar height (A) and symbol color (B) approximate apparent cube color.
Mentions: As with the data for the individual cubes (Figure 4), average color constancy across all cubes under an illumination shift, shown in Figure 5, was generally high but imperfect. To quantify the degree of constancy, it is standard to compute a color constancy index. Such indices seek to frame the data with respect to their position between the constancy and no-constancy predictions, where 1 indicates perfect constancy, 0 indicates a complete failure of constancy, and indices greater than 1 indicate that observers overcompensated for the illuminant shift. From the constancy predictions (illustrated for the four cubes in Figure 4), we computed such an index (see Materials and Methods). Briefly, the color constancy prediction was derived using the assumption that color constant observers would choose the same paint chips in the baseline condition as in the illumination condition; that is, their matches would reflect consistency in surface reflectance, rather than chromaticity.

Bottom Line: As in 2D scenes, we found relatively high but imperfect stability of color judgments under an illuminant shift.In contrast to 2D scenes, we found that background had little effect on average color judgments.Taken together, these results suggest that in real 3D scenes with ample cues to object segregation, the addition of a background may improve stability of color identification.

View Article: PubMed Central - PubMed

Affiliation: COVI Research Lab, Department of Psychology, Rutgers - The State University of New Jersey Camden, NJ, USA.

ABSTRACT
For the surface reflectance of an object to be a useful cue to object identity, judgments of its color should remain stable across changes in the object's environment. In 2D scenes, there is general consensus that color judgments are much more stable across illumination changes than background changes. Here we investigate whether these findings generalize to real 3D objects. Observers made color matches to cubes as we independently varied both the illumination impinging on the cube and the 3D background of the cube. As in 2D scenes, we found relatively high but imperfect stability of color judgments under an illuminant shift. In contrast to 2D scenes, we found that background had little effect on average color judgments. In addition, variability of color judgments was increased by an illuminant shift and decreased by embedding the cube within a background. Taken together, these results suggest that in real 3D scenes with ample cues to object segregation, the addition of a background may improve stability of color identification.

No MeSH data available.