My webpage is here:  http://folk.ntnu.no/williamo/prosjekt2016/bestill.html

The idea is that whenever I press a radio button, the image under should get opacity 1.

It works, but whenever I press a new radio button, the image still has opacity 1, contrary to the expected 0.5, and I don't know why.

Here is the code I use:

1.   radioImages.on("click", function() {
2.     if( ($(this).is(":checked")) ) {
3.       $(this).siblings("img").css("opacity", "1");
4.     } else {
5.       $(this).siblings("img").css("opacity", "0.5");
6.     }
7.   });