Set opacity on background-image with media query

Question

I have a couple of divs, each with a background image. I'm using responsive and adaptive CSS, and when my divs' widths gets less than a certain size(760px btw), the text and some tables with styling becomes hard to read/see with the background image moving in behind them(the background image is on the far right of the text/tables and unobtrusive if the width is above 760px...). So when the width of the viewport gets to 760px and less, I only want the background image to have an opacity...

How do I do that?

So my CSS starts like this:

@media screen and (max-width: 760px){
   background: #cdcdcd url("/images/back.jpg") no-repeat top right;
    /*How do I set the opacity of only the background?*/
} 

Answer 1

You can not change the opacity of a background image, unless you move it to a separate container.

All you can change is the opacity of BG color using rgba() :

background: rgba(0, 0, 0, .5);

Answer 2

You can't set opacity just for a background, but the whole element. You can set opacity of background color (see Zoltan's answer for the example).

---

You can set white <div> over the image and change it's opacity.

<div class="yourImage">
    <div class="imageCover"></div>
</div>

.yourImage {
  background: url(http://blog.stackoverflow.com/wp-content/uploads/stackoverflow-logo-300.png);
  width: 300px;
  height: 83px;
}
.imageCover {
  background: #fff;
  width: 300px;
  height: 83px;
  opacity: .5;
}

Live demo: Tinkerbin

However, this won't work if you don't have a clean background BEHIND your image.