Photos in IMovie are being cropped - and I don't mean the fit / fill option

So I'm trying to make a little video in imovie of a recent holiday and I've just realised that my photos are all being 'trimmed' a little. I know how to adjust the fit / crop to fill / ken burns adjustments but don't know why my pics are coming up a little smaller. Any advice? I'm dragging and dropping them into the app on my macbook straight from iphoto.

I've included the original photo and how it looks in iphoto to show you - any advice from accomplished movie makers very welcome - but in layman's terms please!

Thank you