I wanted to verify that I understood the parameters of drifting grating stim correctly.
If I have monitor refresh rate 60 Hz, then:
temporal_frequency (Hz) = phase_advance * 30, because 0.5 phase corresponds to 1 cycle (psychopy docs)
speed = temporal_frequency / spatial_frequency (degrees/sec) or linear_speed = tf*d(monitor distance)*cot(sf) (cm/s)
Is that correct or I am missing smth?
Code to present 0.2s drifting:
tf = 2 # Hz
spatial_freq=0.05 # cyc/deg
phase_advance= tf/30.0 # monitor refresh rate 60 Hz, 0.5 phase = 1 cycle
orientation_latency=12 # units are in frames? 1/60 = duration of 1 frame. (1/60)12 = 0.2s = 200ms.
speed = tf/sf # degrees/s, cycle - constant; linear_speed = tf*d(monitor distance)*cot(sf) = cm/s
for frameN in range(orientation_latency):
grating2.setPhase(phase_advance, '+')#advance phase by 0.05 of a cycle