Css SiteOrigin Image Widget

Hello,

I would like my images on this page http://espacesacre.ch/spectacles/ to be the same height using the SiteOrigin Image Widget. The purpose is : the images would display the same way on the page whatever their original dimension when I add them in the widget (even if they are a little bit cut in the process it doesn’t matter)

I tried this code in the Style CSS but it doesn’t do the trick :

Could you give me a hand on this please ?
Thank you,
Ciel