Fade between multiple images

Hello !
I'm trying to make a website for a school project, and I would like to add some animations made with CSS.
I found this code on internet :

----------------------------------
CSS
#crossfade > img
{
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0px;
    left: 0px;
    color: transparent;
    opacity: 0;
    z-index: 0;
    -webkit-backface-visibility: hidden;
    -webkit-animation: imageAnimation 30s linear infinite 0s;
    -moz-animation: imageAnimation 30s linear infinite 0s;
    -o-animation: imageAnimation 30s linear infinite 0s;
    -ms-animation: imageAnimation 30s linear infinite 0s;
    animation: imageAnimation 30s linear infinite 0s;
}

#crossfade > img:nth-child(2)
{
    -webkit-animation-delay: 6s;
    -moz-animation-delay: 6s;
    -o-animation-delay: 6s;
    -ms-animation-delay: 6s;
    animation-delay: 6s;
}
#crossfade > img:nth-child(3)
{
    -webkit-animation-delay: 12s;
    -moz-animation-delay: 12s;
    -o-animation-delay: 12s;
    -ms-animation-delay: 12s;
    animation-delay: 12s;
}
#crossfade > img:nth-child(4)
{
    -webkit-animation-delay: 18s;
    -moz-animation-delay: 18s;
    -o-animation-delay: 18s;
    -ms-animation-delay: 18s;
    animation-delay: 18s;
}
#crossfade > img:nth-child(5)
{
    -webkit-animation-delay: 24s;
    -moz-animation-delay: 24s;
    -o-animation-delay: 24s;
    -ms-animation-delay: 24s;
    animation-delay: 24s;
}

@-webkit-keyframes imageAnimation
{
    0% { opacity: 0; -webkit-animation-timing-function: ease-in; }
    8% { opacity: 1; -webkit-animation-timing-function: ease-out; }
    17% { opacity: 1 }
    25% { opacity: 0 }
    100% { opacity: 0 }
}

@-moz-keyframes imageAnimation
{
    0% { opacity: 0; -moz-animation-timing-function: ease-in; }
    8% { opacity: 1; -moz-animation-timing-function: ease-out; }
    17% { opacity: 1 }
    25% { opacity: 0 }
    100% { opacity: 0 }
}

@-o-keyframes imageAnimation
{
    0% { opacity: 0; -o-animation-timing-function: ease-in; }
    8% { opacity: 1; -o-animation-timing-function: ease-out; }
    17% { opacity: 1 }
    25% { opacity: 0 }
    100% { opacity: 0 }
}

@-ms-keyframes imageAnimation
{
    0% { opacity: 0; -ms-animation-timing-function: ease-in; }
    8% { opacity: 1; -ms-animation-timing-function: ease-out; }
    17% { opacity: 1 }
    25% { opacity: 0 }
    100% { opacity: 0 }
}

@keyframes imageAnimation
{
    0% { opacity: 0; animation-timing-function: ease-in; }
    8% { opacity: 1; animation-timing-function: ease-out; }
    17% { opacity: 1 }
    25% { opacity: 0 }
    100% { opacity: 0 }
}
----------------------------------
HTML
<div id="crossfade">
  <img src="http://farm6.staticflickr.com/5145/5576437826_940f2db110.jpg" alt="Image 1">
  <img src="http://farm4.staticflickr.com/3611/3463265789_586ce40aef.jpg" alt="Image 2">
  <img src="http://farm6.staticflickr.com/5263/5601183065_f88a48d599.jpg" alt="Image 3">
  <img src="http://farm2.staticflickr.com/1415/983021323_8eb2f92c01.jpg" alt="Image 1">
  <img src="http://farm1.staticflickr.com/168/397834706_6a46c6ada5.jpg" alt="Image 1">
</div>
----------------------------------

It works, but we can see the background between two images.
What I want is the exact same effect, but without the background.
I tried to modify 25% { opacity: 0 } to 25% { opacity: 1 }, and it worked, but, after a cycle, it stopped to work.

Thanks for reading !