Um diesen unendlichen Bildlaufeffekt zu optimieren, bin ich mir jedoch nicht ganz sicher, wie ich beim Zurückschleifen zum Originalbild einen reibungslosen Übergang schaffen soll. Bei 10s ist es kaum zu bemerken, bei 30s ist es jedoch offensichtlicher. Ich gehe davon aus, dass es etwas mit der Endposition zu tun hat, kann es aber nicht genau bestimmen. Was soll der Wert des letzten Frames sein?

JSFiddle

HTML:

<div class="container">
    <div class="photobanner">
        <img class="first" src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
    </div>
</div>
<div class="container">
    <div class="photobanner">
        <img class="second" src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
    </div>
</div>
<div class="container">
    <div class="photobanner">
        <img class="first" src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
        <img src="http://placehold.it/350x150">
    </div>
</div>

CSS:

.container {
    width: 100%;
    overflow: hidden;
    margin: 10px auto;
    background: white;
}

.photobanner, .photobanner2 {
    height: 233px;
    width: 3550px;
}

.photobanner img, .photobanner2 img {
    padding-right: 10px;
    height: 233px;
    width: 350px;
}

.photobanner img  {
    -webkit-transition: all 0.5s ease;
    -moz-transition: all 0.5s ease;
    -o-transition: all 0.5s ease;
    -ms-transition: all 0.5s ease;
    transition: all 0.5s ease;
}

.photobanner img:hover {
    -webkit-transform: scale(1.2);
    -moz-transform: scale(1.2);
    -o-transform: scale(1.2);
    -ms-transform: scale(1.2);
    transform: scale(1.2);
    cursor: pointer;

    -webkit-box-shadow: 0px 3px 5px rgba(0,0,0,0.2);
    -moz-box-shadow: 0px 3px 5px rgba(0,0,0,0.2);
    box-shadow: 0px 3px 5px rgba(0,0,0,0.2);
}
/*keyframe animations*/
.first {
    -webkit-animation: bannermove 30s linear infinite;
       -moz-animation: bannermove 30s linear infinite;
        -ms-animation: bannermove 30s linear infinite;
         -o-animation: bannermove 30s linear infinite;
            animation: bannermove 30s linear infinite;
}

@keyframes "bannermove" {
 0% {margin-left: 0px;}
 100% {margin-left: -2125px;}
}

@-moz-keyframes bannermove {
 0% {margin-left: 0px;}
 100% {margin-left: -2125px;}
}

@-webkit-keyframes "bannermove" {
 0% {margin-left: 0px;}
 100% {margin-left: -2125px;}
}

@-ms-keyframes "bannermove" {
 0% {margin-left: 0px;}
 100% {margin-left: -2125px;}
}

@-o-keyframes "bannermove" {
 0% {margin-left: 0px;}
 100% {margin-left: -2125px;}
}

.second {
    -webkit-animation: bannermoves 30s linear infinite;
       -moz-animation: bannermoves 30s linear infinite;
        -ms-animation: bannermoves 30s linear infinite;
         -o-animation: bannermoves 30s linear infinite;
            animation: bannermoves 30s linear infinite;
}

@keyframes "bannermoves" {
 0% {margin-left: -2125px;}
 100% {margin-left: 0px;}
}

@-moz-keyframes bannermoves {
 0% {margin-left: -2125px;}
 100% {margin-left: 0px;}
}

@-webkit-keyframes "bannermoves" {
 0% {margin-left: -2125px;}
 100% {margin-left: 0px;}
}

@-ms-keyframes "bannermoves" {
 0% {margin-left: -2125px;}
 100% {margin-left: 0px;}
}

@-o-keyframes "bannermoves" {
 0% {margin-left: -2125px;}
 100% {margin-left: 0px;}
}