Why my photos look awful in Muse?

Hi guys,

I'm having serious problem with images in Adobe Muse CC 2014...

Here attached (on light gray background) how the image looks like in Muse.  On dark gray background, the same image in photoshop.  as you can see, the typographie is barely readable in Muse....

ps : I imported the jpeg image in real size at first, then I doubled the size, but got the same result.  I tried PNG but same result.

(I used to do my site with an obsolete Apple iweb but, even with that old and simple program images looked much crispier!)

any idea ou suggestions?

thanks in advance!