will chao on "How to fit my home page image to screen scale?"

Hello,

I just started working on my second site, here's a problem:

http://agapeportraits.com.au/

The home page image is 1600px wide, it looks fine on my 24 and 27 inch monitors but as soon as the screen resolution falls below 1600px or when i resize the browser, the image is cropped and doesn't resize.

Is there a way to make the image responsible? I am using a prophotoblog.com theme and I assume I have to add a custom CSS code.

I have googled this for hours and couldn't come up with a useful result, please help

Thanks!