On 2015 Sep 29, Lydia Maniatis commented:

No matter how much I tried, I found it impossible to stabilise a sense of how the authors are defining and/or and evaluating photometric effect and geometric effect. The definitions are not straightforward and completely tied to the specific conditions and datasets:

Photometric effect: "The data separate by color in the plots with the separation increasing with the difference between upper and lower plane context illuminant. We refer to this as a photometric effect because, across illuminant context conditions, the geometry is held constant."

Geometric effect: "Finally, there is a geometric effect: The lightness of the probe tab changes as it is moved from the in-plane to the out-plane orientation."

And the analysis: "We quantified the photometric effect for each illuminant change condition as the mean difference between the matches for all probe tabs whose immediate surround was primarily the lower context plane and all matches whose immediate surround was primarily the upper context plane. We quantified the geometric effect for each illuminant change condition as follows. First, we found the slope of the line connecting the pair of data points for each background plane and illuminant change condition (the slopes of the red lines shown in Figure 3; slopes represented in units of change in log10 match reflectance per 90° of tab angle rotation). We then took as a measure of the geometric effect for each illuminant change condition the average of the upper and lower context plane slopes."

The vagueness of the title is explained.

Prizes to anyone who finds this statement intelligible: "Interestingly, the magnitudes of the photometric and geometric effects covaried with the changes in photometric context as revealed by the fact that both scaled linearly with the magnitude of the illuminant change. This is a form of independence: We only need to know the slope of each line to predict the sizes of the photometric and geometric effects for any illuminant change. To put it another way, the relationship between photometric and geometric effects is independent of the size of the illuminant change."

Conclusion: A surface that appears coplanar with a darker one/shadowed will appear lighter than a surface that appears coplanar with a lighter one, but the retinal background will also have some effect. A trivial and predictable result that is almost impossible to make out in this convoluted presentation.

On 2015 Sep 18, Lydia Maniatis commented:

None

On 2015 Aug 16, Lydia Maniatis commented:

The authors of this study describe it as “among the first to measure how variation in both photometric and geometric context affect perceived lightness.” This is a very odd statement, since all stimuli exist in a “photometric and geometric context,” since all of lightness theory directly addresses (and measures) this context, and since the relevance of context is the most fundamental principle of visual perception.

Part of the study simply replicated a classic experiment. Another part added conditions for which there was no theoretical reason to expect an effect, and, indeed, there was no effect.

It is easy to take measurements of anything, including perceived lightness in varying contexts; the point, however, is to choose these contexts in such a way as to test hypotheses, to corroborate or reject assumptions and principles, to learn something new or corroborate something controversial. In confirming that “photometric and geometric context affect perceived lightness” this study just restates the most obvious generality in perception, offering nothing more. The mathematical treatment seems designed to obscure rather than clarify otherwise straightforward results.

For me, this study is part of a wider and sterile tendency in lightness perception (and not only) toward atheoretical “exploration.” Little or no theoretical motivation, lots of data collection, strained calculations and statistical computatons, incoherent discussion, no illumination.

On 2015 Aug 16, Lydia Maniatis commented:

The authors of this study describe it as “among the first to measure how variation in both photometric and geometric context affect perceived lightness.” This is a very odd statement, since all stimuli exist in a “photometric and geometric context,” since all of lightness theory directly addresses (and measures) this context, and since the relevance of context is the most fundamental principle of visual perception.

Part of the study simply replicated a classic experiment. Another part added conditions for which there was no theoretical reason to expect an effect, and, indeed, there was no effect.

It is easy to take measurements of anything, including perceived lightness in varying contexts; the point, however, is to choose these contexts in such a way as to test hypotheses, to corroborate or reject assumptions and principles, to learn something new or corroborate something controversial. In confirming that “photometric and geometric context affect perceived lightness” this study just restates the most obvious generality in perception, offering nothing more. The mathematical treatment seems designed to obscure rather than clarify otherwise straightforward results.

For me, this study is part of a wider and sterile tendency in lightness perception (and not only) toward atheoretical “exploration.” Little or no theoretical motivation, lots of data collection, strained calculations and statistical computatons, incoherent discussion, no illumination.

On 2015 Sep 18, Lydia Maniatis commented:

None

On 2015 Sep 29, Lydia Maniatis commented:

No matter how much I tried, I found it impossible to stabilise a sense of how the authors are defining and/or and evaluating photometric effect and geometric effect. The definitions are not straightforward and completely tied to the specific conditions and datasets:

Photometric effect: "The data separate by color in the plots with the separation increasing with the difference between upper and lower plane context illuminant. We refer to this as a photometric effect because, across illuminant context conditions, the geometry is held constant."

Geometric effect: "Finally, there is a geometric effect: The lightness of the probe tab changes as it is moved from the in-plane to the out-plane orientation."

And the analysis: "We quantified the photometric effect for each illuminant change condition as the mean difference between the matches for all probe tabs whose immediate surround was primarily the lower context plane and all matches whose immediate surround was primarily the upper context plane. We quantified the geometric effect for each illuminant change condition as follows. First, we found the slope of the line connecting the pair of data points for each background plane and illuminant change condition (the slopes of the red lines shown in Figure 3; slopes represented in units of change in log10 match reflectance per 90° of tab angle rotation). We then took as a measure of the geometric effect for each illuminant change condition the average of the upper and lower context plane slopes."

The vagueness of the title is explained.

Prizes to anyone who finds this statement intelligible: "Interestingly, the magnitudes of the photometric and geometric effects covaried with the changes in photometric context as revealed by the fact that both scaled linearly with the magnitude of the illuminant change. This is a form of independence: We only need to know the slope of each line to predict the sizes of the photometric and geometric effects for any illuminant change. To put it another way, the relationship between photometric and geometric effects is independent of the size of the illuminant change."

Conclusion: A surface that appears coplanar with a darker one/shadowed will appear lighter than a surface that appears coplanar with a lighter one, but the retinal background will also have some effect. A trivial and predictable result that is almost impossible to make out in this convoluted presentation.