[Theme TwentyThirteen] Make Header Scale Height & Width to Screen Size

I switched to 2013 from 2011 since I was having major issues with sidebars. Now on 2013 I need to fix the header image on my website. I found a solution that scales the width of the header to the screen size but it does not scale the height so the image looks squeezed. I just want my header to be completely visible and proportional on all screen sizes.