Increment threshold

Whereas absolute thresholds are measured against zero luminance backgrounds, increment thresholds are measured against backgrounds with visible background luminance levels. Select threshold stimulus paradigms to graphically see the difference between absolute and increment threshold stimulus displays.

The increment threshold paradigm is useful when one wishes to selectively measure the sensitivity of one or more of the cone receptors. For example, suppose you wanted to measure the spectral sensitivity of a normal visual system as if it were missing the short wavelength receptors. To accomplish this task an investigator would perform increment thresholds against a very bright blue background. This background would adapt the short wavelength sensitive cones thereby reducing their sensitivity.

Measuring Spectral Sensitivity

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