site logo does not look sharp on mobile device?

Hi im using an upfront theme.
i have uploaded a high res site logo which looks sharp when viewed on desktop computers but when viewed on mobile device it looks fairly blurry ?
is there a way to ensure it remains sharp?

Domain - http://tinyurl.com/plletgb
Screenshot desktop - http://take.ms/e8bow
Screenshot mobile - http://take.ms/qXqxA

Would using a different file format help ? SVG - https://css-tricks.com/using-svg/ ?
Thanks

Tom