Visual Performance and Visual Clarity under Electric Light Sources: Part II—Visual Clarity

Lamp spectrum and spatial brightness at photopic levels: A basis for developing a metric

“…If not, then an investigation of the differences will improve understanding of methodology. While a few studies have done this, 1,32,34,42 and one study at mesopic levels, 109 most do not. It is recommended to include null condition trials as these can detect and quantify the effects of bias.…”

“…A review of definitions reported by researchers suggests an intention by some that brightness and clarity are different phenomena. For example, Vrabel et al 34 provided different definitions for brightness and clarity, implying them to be different, whereas Flynn et al 80 infer that perceptual clarity and spatial brightness relate to the same visual impression and Hashimoto and Nayatani 10 suggested the term brightness sensation to have the same meaning as visual clarity. A comparison of the results of brightness and clarity evaluations, however, suggests that test participants give similar judgements for brightness and clarity when these are not defined in the test procedure.…”

Light source spectrum, brightness perception and visual performance in pedestrian environments: a review

“…In addition to the differences between these models [16][17][18][19][20][21][22][23][26][27][28] , it is important to appreciate that none of them predict any effect of SPD in photopic conditions, yet it is well established that SPD does influence brightness perception in photopic conditions [30][31][32][33][34] . Indeed, there are empirical models for predicting brightness under different light sources in photopic conditions based on this effect 32,[34][35][36][37] .…”

Comment on empirical evidence for the design of public lighting

“…One tendency is for respondents to avoid the ends the response scale leading to a tendency toward the middle region, an effect exaggerated if the scale has an obvious middle category. Peña-García et al report the mean ratings (their Table 2 anchoring a scale is to provide written descriptions of the range, as was done by Vrabel et al [Vrabel et al, 1998]. Surveys need to clearly describe the meaning of questions and anchor the response scale to stimuli to promote consistency [Fotios and Atli, 2012].…”