Why are my fullscreen images being cropped?

Greetings,

I'm using the Momentum template and the images I've uploaded are being displayed at full screen with a slight crop, sometimes vertically and sometimes horizontally, depending on the size of the browser I'm using. If I physically drag the browser to say fit the screen, then image is correctly displayed.
I'm currently using Safari v6.0.5, but it seems not matter what browser I'm using the images are always slightly cropped unless I drag the window to a larger size.

I created each image in Photoshop with a resolution of 1500x1000.

Does it appear to be template issue, or an image size issue?

Here's a link to my page for reference. https://mike-debbie.squarespace.com/neveroddoreven

Thanks,

MD