[Theme: Espied] Image width issue

I have an issue with Espied theme which I’ve seen a couple of times on this forum, but I still haven’t managed to fix it.

The theme supports 1272px width images, but when I load the page the images appear a lot smaller, even though they are 1272 width jpeg files. I think it’s the same issue as this post:
https://wordpress.org/support/topic/picture-issue-2?replies=4

I’ve made a child theme, using the code suggested for style.css and function.php.

What I’ve found so far:
If I include the @import url… it grabs the style.css information from Espied theme which means that the theme has the same issue, but if I remove this line, I get the full width image but none of the other css styling.

Is it actually an issue with the style.css file?

Here is a link to a screenshot of firebug analysis:
http://jamesbarberdesign.net/screenshot.jpg

thanks
James