Hueman theme – custom header size

Using the hueman child theme I’ve added a custom header background image but it doesn’t show the full image: its zoomed in. Can anyone help?

Currently using this on the CSS:

#header {
	background: url(https://chriswhitley.co.uk/wp-content/uploads/2014/07/film-2-e1433258971334.jpg);
	background-size: cover;
	}
}

Site here:
https://www.chriswhitley.co.uk