White flickering between events

I am trying to program a visual attention task using Superlab 4.5 and I am running into some difficulties. The transition between events is choppy and there is a white (horizontal) flicker between each event.

My stimuli are simple BMP files (~3000KB) which include a fixation cross and colored circle against a light grey background. It almost seems like there is a lag between events and/or a screen refreshing issue causing a white flicker each time the stimuli are uploaded.

Any suggestions on how to mitigate this problem would be greatly appreciated!

When you erase the screen it will add a refresh cycle. If the circle is larger then the fixation cross and can cover it, you don’t have have to erase the screen. This should eliminate the lag time.