.started and .stopped columns in output files

OS: Linux
PsychoPy version: 2020.1.2

I’ve some difficulties in understanding the values of “.started” and “.stopped” columns in the output csv files.

Let’s say I have two image components (Img1 and Img2) that I’m showing one after the other in the same routine.

Both components have duration and start defined in seconds with variables.

When looking at the output file, I see something like this:

Img1.started | Img1.stopped | Img2.started 
15.68        | 21.19        | 21.15        

So it seems that Img2 was shown before the end of Img1, is that right?

That’s probably just noise because the switch happens instantaneously. Or maybe the program draws Img2 slightly before so that it exists when Img1 disappears. Does this timing matter a ton for your experiment?

Thanks for your reply Sal. Since this would be an fMRI experiment I would really need to know when stimuli are appearing on screen but from these values I don’t understand if Img2 appears at 21.15 or 21.19.

Oh I see. My guess would be 21.19, because Img2 is drawn before being displayed when Img1 disappears, but don’t quote me on that. Are you using a code component to select/switch the images? If so, maybe you can put console.log(t) next to the line in your code where the images switch so you can compare the outputs?