fullwidth section picture position.

Hi,
I seted up a Fullwidth Section with an image in the background and parallax enabled.
Is there a way to set the position of the picture?
Right now if I’m scrolling the page I only see the upper part of the picture.
And even if I setting a higher section (bigger padding) I still only see the upper parts of the picture.

If I can’t set the position can you at least explain briefly the logic of the picture positioning? (So I can prepare the picture differently..)

Thanks,
John