Spectral sensitivity curves were determined at mesopic luminance levels, 0.1 and 0.01 ft-L, for a 2° field viewed foveally and parafoveally. These data are compared with similar curves for a 10° field, centrally fixated, whose area encompasses the smaller areas studied individually. The results show that, at 0.1 ft-L, differences between the 2° and 10° fields are similar to those between the CIE 2° and 10° photopic curves; furthermore the large field data can be predicted from the 2° data. At 0.01 ft-L however the spectral sensitivity is different from both CIE photopic and scotopic values at all positions and summation within the large field is complex.
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