Remove automatic darkening of header image?

I am playing with design and notice that the header image on the home page is darkened, so that white type becomes more visible. Is there an easy CSS tweak for disabling the darkening, so that the image is nice to look at?

See my test page here:

This appears to work … please correct me if there’s a better way:

.site-header:before {
background: rgba(0,0,0,0);