Image is transparent

Hi everyone (and thanx for this nice theme xxx)
i have a problem when i set an image into one of the circles. i’ve downloaded “Featured Image” plugin and it works great, but when i enter my website i can only see the image when the mouse is over the picture.
i wish to make the image 50% transparent when the mouse is not over, and 100% when the mouse is over.. what to do?

xxx camela