# Onset of Images During Trial- Timing is Off

**URL:** <https://discourse.psychopy.org/t/onset-of-images-during-trial-timing-is-off/40602>\
**Category:** Coding\
**Tags:** timing\
**Created:** [June 27, 2024, 7:50pm UTC](https://discourse.psychopy.org/t/onset-of-images-during-trial-timing-is-off/40602 "2024-06-27T19:50:14Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Rachel\_Foster](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/rachel_foster/32/38649_2.png) [@Rachel\_Foster](https://discourse.psychopy.org/u/Rachel_Foster)\
**Post date:** [June 27, 2024, 7:50pm UTC](https://discourse.psychopy.org/t/onset-of-images-during-trial-timing-is-off/40602/1 "2024-06-27T19:50:14Z")

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Hello,

I am sending messages from PsychoPy to SR Eyelink’s Dataviewer to mark the onset of stimuli during a trial (fixation, stimulus and feedback). In Psychopy, the timing of the onset of the fixation and stimulus is set at consistent times (0 ms into trial for fixation, 500ms into trial for stimulus) and yet the messages that get sent to the stimulus can vary by up to 100ms. Someone on the SR side tried the same code and did not have this happening on their version, and suggested it is likely a problem with the actual time PsychoPy is presenting the images.

Does anyone have experience with PsychoPy being off by ~100ms on presenting stimuli?

Thank you!

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**Author:** ![jonathan.kominsky](https://avatars.discourse-cdn.com/v4/letter/j/a587f6/32.png) [@jonathan.kominsky](https://discourse.psychopy.org/u/jonathan.kominsky)\
**Post date:** [July 15, 2024, 11:13am UTC](https://discourse.psychopy.org/t/onset-of-images-during-trial-timing-is-off/40602/2 "2024-07-15T11:13:41Z")

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You can get small variations some stimuli or the occasional frame drop, but 100ms would be a lot. Are you using an old computer or an older version of PsychoPy?

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<div class="post-metadata">

**Author:** ![Rachel\_Foster](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.psychopy.org/rachel_foster/32/38649_2.png) [@Rachel\_Foster](https://discourse.psychopy.org/u/Rachel_Foster)\
**Post date:** [July 15, 2024, 4:21pm UTC](https://discourse.psychopy.org/t/onset-of-images-during-trial-timing-is-off/40602/3 "2024-07-15T16:21:38Z")

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Thank you for your reply! I decided to code the experiment fully rather than using the builder version with code chunks and now my timings are much more accurate (at most off by 7ms). I am still not sure why this was happening in the builder version unfortunately.