Abstract

We measured sensitivity to sinusoidal temporal modulation as a function of the relative phase of two equally luminant chromatic sources. We previously reported data for three observers at a range of temporal frequencies (OSA 1985); now we report data for a range of observers at a single temporal frequency. The stimuli were presented in a two-channel Maxwellian view system employing red (625-nm) and green (564-nm) light-emitting diodes (LEDs). The two sources were matched by heterochromatic flicker photometry, and their mixture was metameric to ~600 nm. The radiance of the LEDs was controlled by computer-driven electronic circuitry that provided a linear response up to 900 td/LED. A 350 td, 2° test field was superimposed on 8°, 600-nm adapting fields of 100 and 1000 td. We measured modulation sensitivity to 6-Hz flicker for eighteen phases from 0° to 340° and computed an axis of symmetry. Color-normal males had phase axes in the range of 123–173° and 112–156° for adapting fields of 100 and 1000 td (that is, stimulus condition red-leads-green gives minimum sensitivity). In comparison, color-defective males had phase axes of 176–184°. We discuss the data in terms of cone density ratios.

© 1986 Optical Society of America