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James Schirillo, Matthew Riddle, Rumi Tokunaga, Alexander Logvinenko; Can luminance contrast be estimated with real light?. Journal of Vision 2010;10(7):422. doi: 10.1167/10.7.422.
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© ARVO (1962-2015); The Authors (2016-present)
In that numerous studies have shown that humans can match the luminance contrast between edges generated on a CRT monitor, it should be possible to match a crisp luminance edge produced by a spotlight to a luminance edge produced by a reflectance edge in a natural scene. In one experiment we had 40 naïve observers match the luminance contrast of a luminance edge produced by a spotlight to one of 20 reflectance edges. In a second experiment we had the same observers match the lightness of the region lit by the spotlight to one of the same 20 reflectance edges. The luminance ratio produced by the spotlight was 15:1, where its luminance was 22.4 cd/m2, and its area was 9.0° X 4.9° visual angle. The size of each of the 20 reflectance papers was 0.72° X 0.72°. We found, first, large inter-individual variations with the luminance match covering a ∼15:1 range, suggesting that observers cannot make an accurate luminance match unlike CRT screen performance. Second, observers made the histograms of lightness and luminance matches very close to each other, suggesting that when asked to make a luminance match they actually performed a lightness match. Lastly, the luminance contrast averaged ∼ 6.33:1 for both luminance contrast matches and lightness matches. This underestimates the actual luminance contrast produced by the spotlight by 42%. These findings suggest that observers cannot estimate the luminance contrast produced by real objects lit by real light sources. Whether these findings conflict with what has been reported for luminance contrast matches with a CRT screen will be discussed.
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