Hello,

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?**

Thanks,

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

angle_iteration=30

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
grating2.draw()
mywin.flip()
```