QGraphicsView Performance displaying QImage is faster with QRectGraphicsItem

Hello,

i wrote a software that loads images frame by frame, and displays them in a graphis view (QOpenGLWidget) triggered by a QTimer with 1000Hz (so im trying to process as fast as possible, if the previous processing did not happen yet then it gets rejected).

In the processing Im loading FULLHD grayscale images from my SSD.

The speed that im measuring is around 80 fps. But when i add a QGraphicsRectitem to the scene, then i get 120 fps. Does this make sense?

So in every loop what i do is that i store the QImage in a member variable. I have another QTimer triggered display loop that actually updates the QImage in the scene with 60Hz. Both, loading the image and displaying it are in the same thread.

Does anybody know why i get a faster performance with an extra object in the scene?