CSS :after hover Transition

The HTML structure

<div id="small_gal">
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
    <div><img src="images1.jpg" /></div>
</div>

The images are having dropshadows so border is not a solution, as it will be outside the image

The border is having transition and it works smoothly on FF but not in chrome or other browsers

Here is the code which I have used

#small_gal div:hover{cursor: pointer;}
#small_gal div:after {
    content: '';
    position: absolute;
    width: 112px;
    height: 81px;
    border: 3px solid #e27501;
    left: 9px; top: 9px;
    z-index: 9;

    opacity: 0;
    -webkit-transition: opacity 0.5s ease-in-out;
    -moz-transition: opacity 0.5s ease-in-out;
    -o-transition: opacity 0.5s ease-in-out;
    -ms-transition: opacity 0.5s ease-in-out;
    transition: opacity 0.5s ease-in-out;
}
#small_gal div:hover:after {
    opacity: 1;
}

Note:

#small_gal

is only the container each image is wrapped in a div so we can implement :after