Abstract
The functional visual field for detecting a colored target out of colored background was determined for various luminance levels covering a range of 0.15 cd/m2 through 30 cd/m2. The background was consisted of two different colors distributed randomly over the field, each color element having a size of 2°×2° arc of visual angle. The visual field had a normal size of about 20° diameter when transformed into an equivalent circular from with a high luminance level, but it contracted down to 8° with the lowest luminance level employed. The importance to keep the luminance level above about 1.5 cd/m2 was shown in order to avoid an extreme contraction of the functional visual field size under the experimental conditions investigated.
