Best way to code very short image presentations

Coding
1

Hi,

I am building a visual masking experiment and image presentation is very important. I need to make sure that I present images for the shortest possible duration for a 60Hz Monitor, which I believe is something like 16-17ms. I build my task in the coder. And the way I execute my presentation times is with a while loop. Something like this:

# Get images onset, show images, draw fixation cross, flip and wait
image_onset = global_clock.getTime()
current_target.draw()
current_distractor.draw()
fixation_cross.draw()
win.flip()

while global_clock.getTime() < image_onset + image_duration:
    pass

# Get images offset and measure actual image duration
image_offset = global_clock.getTime()
actual_image_duration = image_offset - image_onset
print(f"Trial {i}: Image duration = {actual_image_duration}")

where image_duration=0.017

Do you think this will do what I am asking it to do or likely my code will fail in reality due to the extremely short duration I need? So having the double of that time already messes up with my task.

If you have any other solutions to my problem which may be more precise please let me know.

2

If you want just one frame then why wait at all? You could flip to present the image and then flip again to hide it.

3

Is the while loop method likely to fail? also will it be possible to ask how to edit the code? Would it be something like this:

image_onset = global_clock.getTime()
current_target.draw()
current_distractor.draw()
fixation_cross.draw()
win.flip()
—> win.flip()

4

Hello @antoniyaaboyanova

As I read the code, fixation_cross is displayed for the same duration as the images current_targert and current_distractor (image_duration) because all three stimuli are flipped together and then remain visible until the end of the while loop. I think that you need two win.flip to show the fixation cross for one refresh. One to show target, distractor and fixation cross and a second to show the target and the distractor. Then comes your while-loop.

Best wishes Jens